Self-Powered Sensing and Wireless Communication Synergic Systems Enabled by Triboelectric Nanogenerators

Abstract

With the rapid advancement of the Internet of Things (IoT) era, the demand for wireless sensing and communication is increasingly prominent. Tens of thousands of sensing and communication nodes have presented new challenges to distributed energy. As a green energy harvesting technology, the triboelectric nanogenerator (TENG), with its outstanding characteristics of simple configuration, low cost, and high compatibility, demonstrates significant advantages in self-powered sensing systems and great application potential in the fields of human–machine interaction and wearable devices in the IoT era. More importantly, the electric displacement field and modulated electromagnetic waves that TENG triggers have opened a new paradigm for self-powered wireless communication, making up for the disadvantages of power supply by traditional distributed power sources. This review comprehensively discusses the latest scientific and technological progress in wireless communication technology prompted by TENG and further discusses its potential applications in various promising fields. Finally, a summary and outlook of TENG-based self-powered sensing and wireless communication synergic systems are presented, aiming to stimulate future innovation in the field and accelerating the paradigm shift to a fully self-powered IoT era.

1. Introduction

With the continuous development of 5G communication technology and the era of the Internet of Things (IoT) [1,2,3,4,5,6,7,8,9,10,11,12,13], the landscape of trillions of widely distributed sensor nodes has become a reality. They are intricately woven into various environments, executing real-time surveillance and acquisition of crucial physical parameters such as temperature, humidity, pressure, and lighting, which further cooperate with communication modules for synchronized transmission of the sensor signals [14,15,16,17,18,19,20,21,22,23,24,25,26]. Among different communication methods, wireless communication is highly favored due to its ability to facilitate long-distance signal transmission without the constraints of external cables, significantly reducing work costs and enhancing system flexibility [23,27,28,29,30,31,32,33,34,35]. The proliferation of sensor and communication networks has extensively promoted the perception and interaction of the external environment, providing vital data support for fields such as smart cities, intelligent oceans, and health monitoring [3,27,28,29,36,37,38,39,40,41,42,43,44,45]. Currently, most sensor and communication nodes adopt batteries as power sources, which to some extent solves the shortcomings of complex wiring and low flexibility associated with traditional cable-based power supply. However, the large size, short lifespan, high renewal and maintenance costs, and potential environmental impacts of batteries bring new challenges for distributed power sources in the burgeoning IoT ecosystem.

Green nanotechnology for energy collection offers a potential solution for distributed power sources, such as electromagnetics, optoelectronics, thermoelectrics, piezoelectrics, and triboelectrics, which can successfully collect environmental energy and convert it into electrical energy to power systems, demonstrating the advantages of sustainable use and environmental friendliness [46,47,48,49,50,51,52,53,54,55]. Among them, the triboelectric nanogenerator (TENG) based on the coupling effect of contact electrification and electrostatic induction is a new energy-harvesting technology proposed by Zhong Lin Wang et al. in 2012 [56], which presents the irresistible advantages of a wide material selection range, simple structure, and low cost [46,57,58,59,60]. In systems powered by TENGs, sensors, microcontroller units, and wireless transmission circuits are normally integrated to achieve signal perception and communication. For example, Yu et al. reported a fully self-powered wireless sensor node that utilizes TENGs to collect vibration energy and provide power in situ to the sensor and wireless communication module, ultimately achieving long-distance wireless transmission of temperature and humidity signals [34]. Additionally, leveraging TENGs’ sensitivity to external stimuli, they can also function as self-powered sensors for signal perception, with broad applications in wearable sensing and human–machine interaction [44,61,62,63,64,65,66,67,68,69]. Representatively, they can be weaved into clothing to monitor human movement, which would generate electrical signals of varying intensities with the change in motion amplitude [70]. On this basis, an integrated TENG system without an external power supply has been developed, where the TENG not only serves as a sensor for information perception but also collects energy for powering wireless communication modules [71,72].

However, it must be mentioned that considering the high output impedance of TENGs, it is challenging to directly apply them to traditional electronic systems, where power management circuits are usually required to address impedance mismatch issues [15,73,74,75]. Furthermore, higher power outputs generally necessitate larger-sized TENGs, limiting the system’s application scenarios and significantly increasing complexity and cost. Although TENGs can be applied as self-powered units to achieve sensing functions free from external power supply, wireless communication modules such as Bluetooth, Zigbee, and Wi-Fi still require a power supply.

Recently, researchers discovered and proposed a new scheme for self-powered wireless communication systems based on TENGs utilizing tuning electromagnetic waves or the electric displacement field generated by triboelectric charges during TENG operation for wireless communication [76,77,78,79]. Moreover, by integrating TENG-based self-powered sensing, a new type of self-powered wireless sensing and communication system has been constructed [79,80,81,82], which demonstrates unique advantages. On the one hand, the triboelectric effect brings the ability to collect energy and self-powered sensing signals from mechanical motions. On the other hand, the electric displacement field or electromagnetic wave excited by the TENG is capable of wirelessly transmitting embedded sensing signals in the absence of cables and power modules, representing one of the development trends in the IoT era.

To summarize the technical innovation and rapid advancements, this review comprehensively presents the fundamental operation principles, structural designs, and application scenarios of novel self-powered sensing and wireless communication synergic systems enabled by TENGs. Starting from Maxwell’s displacement current, the fundamental working principles and modes of TENGs are illustrated. Moreover, the self-powered wireless communication models triggered by TENGs are explored and established in detail, and a comprehensive analysis of the current optimization strategy is provided. Additionally, their broad application scenarios in underwater environments, smart transportation, human–machine interaction, etc., are summarized. Finally, the challenges and prospects of TENG-based self-powered sensing and wireless communication synergic systems are discussed. The technology of directly using TENGs for self-powered sensing and wireless signal transmission offers the advantages of miniaturization, high integration, and potent portability, providing an effective solution for realizing emerging fully self-powered wireless sensing and communication in the new era (Figure 1).

2. Principles of TENGs

2.1. Maxwell’s Displacement Current

Maxwell established and improved a set of differential equations in the 19th century to describe the relationship between electric field, magnetic field, charge density, and current density, named the Maxwell equations:

$$𝝯·\mathit{E}={\displaystyle \frac{\rho }{{\epsilon }_0}}$$

(1)

$$𝝯·\mathit{B}=0$$

(2)

$$𝝯\times \mathit{E}=-{\displaystyle \frac{𝜕\mathit{B}}{𝜕\mathrm{t}}}$$

(3)

$$𝝯\times \mathit{B}=-{\mu }_0\left(\mathit{J}+{\epsilon }_0{\displaystyle \frac{𝜕\mathit{E}}{𝜕\mathrm{t}}}\right),$$

(4)

where $\mathit{E}$ and $\mathit{B}$ represent electric and magnetic fields, respectively, $\mathit{J}$ is current density, $\rho$ is charge density, ${\epsilon }_0$ refers to vacuum dielectric constant, and ${\mu }_0$ is vacuum permeability. Maxwell’s equations provide a universally applicable electromagnetic theory, which states that a changing electric field produces a magnetic field, while a changing magnetic field conversely induces an electric field, laying the theoretical foundation for the opening of the radio era. Among them, the bold assumption and introduction of displacement current are the important basis for establishing Maxwell’s equations, which compensates for the shortcomings of Ampere’s law in dealing with changing electric fields:

$${\mathit{J}}_{\mathit{D}}={\displaystyle \frac{𝜕\mathit{D}}{𝜕\mathrm{t}}}={\epsilon }_0{\displaystyle \frac{𝜕\mathit{E}}{𝜕\mathrm{t}}}+{\displaystyle \frac{𝜕\mathit{P}}{𝜕\mathrm{t}}},$$

(5)

in which ${\mathit{J}}_{\mathit{D}}$ is displacement current density, D is the displacement field, and P represents the polarization field. According to Maxwell’s theory, this fundamental part is independent of the motion of charges and is essentially an electric field that changes over time. Maxwell postulated that displacement current elicits a magnetic field in the same manner as conduction current; specifically, the fluctuation of the electric field stimulates a magnetic field in the adjacent space. Based on Maxwell’s displacement current, academician Zhong Lin Wang proposed that the second term of displacement current is fundamentally related to the output signal of the nanogenerator, and it is supposed that displacement current is the only conduction mechanism for TENG power transmission [83].

2.2. Equivalent Circuit Model of Capacitor and First-Order Lumped Parameters

For any TENG, a pair of triboelectric layers are used for contact charging, providing static polarized charges. Under mechanical forces, the electric field composed of static polarized charges on the triboelectric layer surface constantly changes, thus driving electrons to flow between external electrodes. Assuming that the amount of transferred charge on the outer electrode is Q, and supposing that triboelectric charge does not exist, the structure can be regarded entirely as a capacitor (Figure 2a). Therefore, its contribution to the voltage between the two electrodes is $-Q/C\left(x\right)$, where $C$ is the capacitance between the two electrodes and $x$ is the distance between the two electrodes. Meanwhile, the contribution of the surface charge of the triboelectric layer to the voltage is defined as $V_{OC}\left(x\right)$, which is the open-circuit voltage output of the TENG. According to the principle of potential superposition, the total voltage potential difference between the two electrodes can be expressed as

$$V=-{\displaystyle \frac{Q}{C\left(x\right)}}+V_{OC} \left(x\right)$$

(6)

This equation describes the $V–Q–x$ relationship of a TENG, which is the governing equation for any TENG, clearly characterizing the inherent capacitive behavior of a TENG.

Further, from this governing equation, the lumped parameter equivalent circuit model can be easily derived [84], as shown in Figure 2b. Specifically, a variable capacitor is used to represent the capacitance term (first term) in Formula (6), and an ideal voltage source describes the open-circuit voltage term (second term) in Formula (6). This model is suitable for any TENG analysis.

2.3. TENG-Based Energy Harvesting and Self-Powered Sensing

Macroscopically speaking, the working principle of TENGs is based on the coupling effect of contact electrification and electrostatic induction. Commencing with the TENG’s classic contact-separation (CS) mode, the working process of a TENG is presented. As shown in Figure 2c(i), when two different materials come into contact under forces, the different electron affinities of the two materials will result in equal charges with opposite polarity on each surface, i.e., contact electrification. At this stage, these charges almost overlap in the same plane, thus presenting an overall charge balance state. After the external forces are removed, the two materials separate from each other and gradually move away. The surface charges on the triboelectric layers, as immobile charges, would induce freely moving charges on the electrodes, which flow in the external circuit driven by the potential difference (Figure 2c(ii)). When the two triboelectric materials are completely separated, a new electrostatic equilibrium state is reconstructed again (Figure 2c(iii)), and no charge flow is observed on the external circuit. With the process of the two materials approaching again under force, the opposite transversion occurs, and reversely flowing electrons can be observed in the external circuit until they come into complete contact again (Figure 2c(iv)). By continuously applying periodic forces externally, periodic stable currents can be obtained in external circuits.

Since the first report on TENGs in 2012, they have been explored to collect energy from various mechanical activities, including low-frequency human motion energy such as walking and jumping, as well as environmental energy like wind and hydropower [57,85,86,87]. More importantly, TENGs can display sensitive electrical signal outputs (voltage, current, and charge) to different external stimuli without the involvement of external power sources. This unique attribute has propelled their widespread adoption as self-powered sensors, demonstrating remarkable performance in wearable sensing, health monitoring, and smart home applications [61,62,63,88]. Generally speaking, TENGs can be divided into four working modes (Figure 2d). In addition to the classic CS mode, TENGs also include lateral-sliding (LS) mode, single-electrode (SE) mode, and freestanding triboelectric-layer (FS) mode to cover the application breadth in multiple scenarios. The CS-mode TENG performs well in small vibrations and is suitable for low-frequency energy harvesting [63,89]. TENGs in linear LS mode utilize continuous lateral sliding to generate electrical energy, which can provide more stable energy output in specific continuous motion scenarios [90,91]. TENGs in SE mode considerably simplify the structural design, and the setting of a single electrode gives the triboelectric layer greater degrees of freedom [92,93]. Additionally, the FS mode works effectively in dynamic environments and is particularly well suited for applications that necessitate adaptability to fluctuating environmental conditions [94,95]. It is worth mentioning that multimodal TENGs can be used in collaboration to meet the complexity of practical work scenarios.

2.4. TENG-Triggered Self-Powered Communication Model

From the above principle analysis, it can be seen that during TENG operation, the electric displacement field constantly changes, which is one of the basic ideas for TENGs to achieve wireless communication. As shown in Figure 3a, an electrostatic simulation conducted using COMSOL focuses explicitly on the triboelectric layers, where it can be seen that there are different space potential distributions around the dielectric loaded with triboelectric charges. If a collector, i.e., an electrode, is placed within the coverage area of the electric displacement field, the TENG’s electrical signals can be collected on the electrode. In essence, the energy induced by the TENG can be transmitted to external space through changes in the intrinsic electric displacement field for wireless sensing and communication.

If one of the triboelectric layers is wired to a transmitting electrode, as most research works call it [96], the alternating current signal generated by the TENG under external stimulation would flow sequentially to the transmitting electrode and induce an electric field ${\mathit{E}}_{\mathbf{0}}$ in the surrounding environment. As shown in Figure 3b, the positive and negative charges move in the dielectric medium between the transmitting electrode and receiving electrode and generate a polarization electric field ${\mathit{P}}_{\mathbf{0}}$. Under the coupling effect of the electric field and polarization electric field, the electric displacement field ${\mathit{D}}_{\mathbf{0}}$ from Maxwell’s equation is expressed as follows [97]:

$${\mathit{D}}_{\mathbf{0}}={\epsilon }_0{\mathit{E}}_{\mathbf{0}}+{\mathit{P}}_{\mathbf{0}}$$

(7)

The polarization of the dielectric medium is represented as

$${\mathit{P}}_{\mathbf{0}}=\left({\epsilon }_r-1\right){\epsilon }_0{\mathit{E}}_{\mathbf{0}},$$

(8)

where ${\epsilon }_r$ is the relative dielectric constant of the dielectric medium; therefore,

$${\mathit{J}}_{\mathit{d}}={\displaystyle \frac{𝜕{\mathit{D}}_{\mathbf{0}}}{𝜕\mathrm{t}}}={\epsilon }_0{\displaystyle \frac{𝜕{\mathit{E}}_{\mathbf{0}}}{𝜕\mathrm{t}}}+{\displaystyle \frac{𝜕{\mathit{P}}_{\mathbf{0}}}{𝜕\mathrm{t}}}={\epsilon }_r{\epsilon }_0{\displaystyle \frac{𝜕{\mathit{E}}_{\mathbf{0}}}{𝜕\mathrm{t}}}$$

(9)

It can be seen that the induced displacement current is closely related to the relative dielectric constant of the medium [97]. As for the equivalent model in Figure 3b, the conduction current is equal to the displacement current, which means that the relative dielectric constant determines the current measured in the receiving electrode. Therefore, the structure is more conducive to signal transmission in environments with high dielectric constants, such as marine environments rich in various ions.

However, this electric displacement field rapidly decays in the environment for conventional airfields, thereby limiting the effective signal transmission distance. The communication distance can be expanded if a rapidly changing term can be introduced into the circuit to generate electromagnetic wave signals, as proposed by Zi’s group [98]. Considering the high voltage output of TENGs, a pair of electrodes designed to facilitate electrostatic breakdown can be developed into the circuit composed of TENGs, as shown in Figure 3c. When the induced electric field of a TENG is stronger than the threshold breakdown voltage of air, the gas medium undergoes collision ionization under the action of the electric field and brings about penetrating discharge between electrodes. During this process, molecules in the air are ionized to form charged ions and electrons, giving rise to a current burst. Correspondingly, the alternating changes in the electric and magnetic fields are formed, resulting in the propagation of electromagnetic waves in the air. At this point, the antenna can be applied to receive omnidirectionally wireless electromagnetic wave signals induced by breakdown discharge, thereby achieving the purpose of signal communication.

In addition, the TENG capacitor model proves that it can be equivalent to a series circuit of an ideal voltage source and a capacitor. In this case, if an inductor is connected in the circuit, it is coincidentally the basic circuit model of an inductor–capacitor (LC) oscillation circuit. Therefore, wireless long-distance transmission of signals can be achieved by coupling inductors with TENGs (Figure 3d). During the working process of TENGs receiving external mechanical stimulation, the generated energy continuously and periodically supplies power to the circuit, and the magnetic field is generated during the repeated charging and discharging process of the capacitor and inductor. As a result, the electromagnetic waves are emitted through the antenna or directly through the inductor, and the frequency can be expressed as

$$f={\displaystyle \frac{1}{2\pi \sqrt{LC}}}$$

(10)

At the receiving end, an antenna or inductor coil is applied to receive the electromagnetic wave signal, thereby achieving wireless communication driven by TENGs. Compared with systems based on inherent displacement current, combining TENGs with inductive oscillation circuits can generate frequency-controllable electromagnetic fields.

3. Optimization Strategy of TENG-Enabled Wireless Communication System

By employing the aforementioned mechanisms, the high-voltage electrical signals originating from TENGs can be directly transmitted wirelessly via electric displacement fields or converted electromagnetic signals, thereby eliminating the additional process of extracting energy from power modules and possible complex intermediate steps. Here, we summarized the specifics of wireless communication methods based on various modes and presented optimization strategies to enhance their efficacy.

Table 1. Communication characteristics of different models (CS, SE, and FS under “Operating Mode” are abbreviations for contact-separation, single-electrode, and freestanding triboelectric-layer, respectively).

Communication Model	Signal Characteristics	Triboelectric Materials	Sizes	Operating Mode	Transmitted Signal Amplitude	Receiving Signal Amplitude	Communication Distance (Medium)	Ref.
Electric displacement field (via plane electrode or tribo-charged surface)	Typical pulse waveform/resonant waveform	gPLA/Teflon	16 × 18 cm2	SE	~1500 V	\	3 m (in air)	[76]
		PA6/PTFE	5 × 5 cm2	CS	1950 V	710 mV	2.3 m (in air)	[99]
		Al/FEP	4.5 × 4.5 cm2	SE	13 V/14.5 μA	~2 μA	~100 m (in water)	[96]
		Nylon 66/Ni-MOF/PVDF CNF	3 × 3 cm2	SE	45 V/0.77 μA	~3 nA	5 m (in water)	[81]
		Al/PTFE	153.86 mm2	CS	345.2 V/29.2 μA	\	220 m (in water)	[100]
Modulated electromagnetic wave (via breakdown discharger)	Resonant waveform	Skin/FEP	9 × 9 mm2	\	\	\	30 m (in air)	[98]
		PA66/FEP	5 × 5 cm2	CS	600 V	~0.2 V	5 m (in air)	[82]
Modulated electromagnetic wave (via coupling inductor coil)	Resonant waveform	PA6/PDMS	4 × 5 cm2	CS	~1000 V	\	~45 cm (in air)	[101]
		PA66/FEP	5 × 5 cm2	CS	1700 V	~500 mV	90 cm (in air)	[102]
		PA66/FEP	\	CS	590 V	~500 mV	1 m (in air)	[103]
		Rabbit fur/PTFE	530 mm2	FS	~1000 V	3 V	40 m (in air)	[104]
		PA6/PDMS	4 × 4 cm2	CS	~50 V	25 mV	~12 cm (in air)	[105]
		Nitrile/Ecoflex	8 × 8 cm2	CS	~100 V	\	1 m (in air)	[106]

showcases the distinctive system attributes derived from different communication models grounded in TENG technology.

3.1. Electric Displacement Field with TENG Itself

This “new wireless paradigm” of wireless communication was first proposed in 2017, which utilizes the powerful electric field of TENGs [76]. In their work, Mallineni et al. prepared a high-performance TENG based on graphene–polylactide (gPLA) nanocomposites using 3D printing. As shown in Figure 4a, it has a single-electrode structure, using gPLA as both the electrode and the triboelectric layer, with polytetrafluoroethylene acting as the counter triboelectric layer. It is worth noting that due to the presence of graphene, simple manual tapping can generate an output voltage of up to 2 kV by this TENG. Then, through connecting the copper (Cu) strip as a wire to the gPLA electrode, a high electric field is generated at the end of the Cu strip due to its high output voltage, which can be wirelessly transmitted within a distance of 3 m.

Innovatively, Figure 4b showcases an electrode-free TENG utilizing polypropylene (PP) and polymethyl methacrylate (PMMA) as the triboelectric layers, facilitating wireless communication through their rotational motion [107]. Owning to different electron affinities, PP and PMMA surfaces generate opposite polarization charges. During the rotation process, the periodic changes in charge distribution lead to alteration in the surrounding electric displacement field. Therefore, by placing a collector within this range of variation, energy signals from the electrode-free TENG are successfully collected. Meanwhile, by increasing the number of collector electrodes placed in the electric displacement field, a linearly increasing short-circuit current is received. Furthermore, Jie et al. proposed an integrated rotating TENG with electrode and electrode-free modes to compensate for the low efficiency of the space leakage electric field [77], which may be more favored in energy harvesting.

Subsequently, by introducing the transmitting electrode into the system, Tang et al. demonstrated that stable synchronous signals can be induced at the receiving electrode within a transmission distance of 9 mm [108] (Figure 4c). Unlike TENGs’ voltage output of up to the kV level in previous works, this small signal of around 200 V is also able to achieve short-distance wireless communication. Moreover, experiments have shown that the presence of obstacles such as walls in the environment does not affect the quality of wireless communication, which can be equivalent to capacitors connected with TENGs.

By extending the approach to water environments, the communication by the electric displacement field remains viable. It typically demonstrates a longer distance owing to water’s inherently higher dielectric constant than air [97,100,109]. Ma et al. placed an emitting electrode connected to the TENG triboelectric layer in water and studied the effect of the dielectric constant on communication quality [97]. It can be observed from Figure 4d that the induction signals of the receiver end immersed in different phases exhibit evident differences. Compared with the original signal of the TENG, the waveform and amplitude of the communication signal received in the water phase almost remained unchanged. In contrast, the amplitude of the signal received in the air phase was significantly reduced, which is consistent with the above theoretical analysis in Section 2.4.

Additionally, longer communication distances can be performed by adjusting the ion concentration in the water by adding salt or acid–base, which can be attributed to the enhanced electric displacement field due to the abundant free-moving ions under the underwater electric field [96]. For example, Zhao et al. achieved high-signal-to-noise-ratio wireless communication in a 100 m long saltwater pipe [96]. Throughout the process, the signal waveform remained undistorted, with a mere 66% reduction observed in its peak value (Figure 4e).

Improving the electrical output performance of TENGs can also improve the quality of wireless communication. Therefore, Zhang et al. constructed a fully symmetrical TENG structure to achieve omnidirectional water wave energy collection, as shown in Figure 4f [100]. This structure remarkably optimizes the output power of the TENG and ultimately carries out delay-free ultra-long-distance communication up to 220 m (Figure 4f). The self-powered wireless communication method triggered by the electric displacement field of the TENG provides the possibility of developing alternative wireless communication in complex underwater environments.

3.2. Modulated Electromagnetic Waves by TENG with Breakdown Discharge

Unlike the signal communication method based on the electric displacement field generated by the TENG itself, recently, the adoption of high voltage generated by TENGs to induce breakdown discharge between two electrodes for signal transmission has been reported as a new wireless transmission approach [110]. Typically, this communication model requires a pair of specially designed “tip electrodes” for a more efficient discharge process. As shown in Figure 5a, Zi’s group proposed a self-powered wireless sensing electronic sticker triggered by a TENG with breakdown discharge [98]. Besides flexible materials of fluorinated ethylene propylene (FEP) and polydimethylsiloxane (PDMS) as the triboelectric layers, the pair of specially designed electrodes is the most critical part. As discussed in Section 2.4, breakdown discharge occurs in this pair of tip electrodes due to the collision of high-speed moving electrons with air molecules driven by the strong electric field of the TENG. During the breakdown discharge process, air molecules undergo a transformative reaction, generating ions and fresh electrons that coalesce into an electron avalanche, ultimately culminating in the formation of plasma [111]. This dynamic process generates rapidly fluctuating displacement currents, which in turn induce wireless electromagnetic signals. In this groundbreaking work, the device seamlessly transitions from input motion signals to electromagnetic wave signals, triggered by a simple finger swipe on the TENG, showcasing its unparalleled self-powered and wireless communication capabilities. The emitted signals predominantly resonate within the VHF band, enabling a remarkable transmission distance of up to 30 m. Remarkably, the device boasts an ultra-thin profile of merely 95 μm, encapsulated within a compact area of 9 mm × 9 mm and a feathery weight of 16 mg, epitomizing miniaturization, light weight, and exceptional flexibility. Compared to conventional self-powered near-field communication systems, this design offers pronounced advantages in terms of both transmission range and device dimensions. Furthermore, the wireless system emits omnidirectional resonant signals, eliminating the need for traditional antenna “alignment” at the receiving end [101,103,104], and greatly enhancing convenience and versatility. Nevertheless, a limitation lies in the fact that the emission signals generated through breakdown discharge in this work remain unmodulated, carrying limited information content. Consequently, they are predominantly utilized as switching triggers rather than serving as accurate and stable sensing signals rich in diverse information, which thereby restricts their broader application potential.

In response to this challenge, Luo’s group proposed a self-powered dual-parameter omnidirectional wireless sensing system based on a symmetrical resonant circuit [112]. As shown in Figure 5b(i), by utilizing a compact and symmetrical resonant circuit, the output signal of the TENG is ingeniously modulated into different resonant frequency signals determined by capacitors $C_x$ and $C_y$. Within this framework, the frequency of electromagnetic signals generated by electrical breakdown is mainly concentrated in the range of 50–300 MHz, while the resonant frequency of symmetrical resonant circuits is strategically designed to be less than 50 MHz to ensure mutual non-interference. The graph clearly illustrates that the received signals, captured by the short-circuit antenna wrapped with copper wire at the receiving end, exhibit distinctly identifiable resonant peaks (Figure 5b(ii,iii)). With the change in $C_x$ or $C_y$, the resonance peaks at the receiving end shift accordingly, signifying the potential to transmit even richer information. Specifically, only when $C_x$ changes does the spectrogram peak related to $C_x$ of the received signals change, while the peak related to $C_y$ remains stable, and the same goes for $C_y$, as shown in Figure 5b(iv,v). Furthermore, the adoption of the dual-antenna configuration improves accuracy and stability, marking a major step forward in the field.

Additionally, Zi’s group has further explored a universal solution for sensing and communicating different physical signals by coupling the electromagnetic wave generated by the triboelectric effect with commercial sensors, achieving a universal solution suitable for sensing various physical signals [113]. As shown in Figure 5c, the TENG with breakdown discharge capability connected to commercial sensor devices is simplified into a resistor-LC (RLC) circuit, where the natural frequency and damping ratio of the system are determined by $f=1/(2\pi \surd LC)$ and $\zeta =R/(2\surd (L/C\left)\right)$, which can be characterized by the oscillation base frequency and decay time in wireless signals. Essentially, modulation of the wireless transmission signals is achieved through alterations in the resistance, inductance, and capacitance parameters introduced by the sensor. This work also discussed signal coupling methods of a resistance-based self-powered wireless sensing solution (TDE-SWIS), a capacitance and inductance-based TDE-SWIS, and a parallel resistance and capacitance-based TDE-SWIS, respectively, demonstrating the communication capability of transmitting multiple physical signals via electromagnetic waves and high adaptability to different scenarios. Further, the design of multi-point sensing integrated devices demonstrates the advantages of communication based on TENG-triggered breakdown discharge in fully self-powered, integrated, long-distance, and wireless scenarios. Additionally, the study provided a thorough analysis of the impact of ambient temperature and humidity on communication quality. Notably, while the modulated signals exhibit minimal dependence on temperature variations, they are susceptible to humidity changes to a certain extent.

This innovative wireless transmission method, rooted in breakdown discharge technology, is highly coveted owing to its exceptional high-frequency performance and remarkable long-range capabilities. Nevertheless, the current research landscape surrounding this methodology remains limited in scope and depth, pressing the necessity for a concerted effort to unravel its untapped potential and vigorously propel its advancement.

3.3. Modulating Electromagnetic Waves by TENG Coupling Inductor

By ingeniously integrating a TENG with an inductor, researchers have successfully validated an efficient and concise wireless communication strategy that cleverly utilizes the inherent capacitive characteristics of TENGs as a driving source to form an LC circuit for signal communication [78,114]. Some research works also mentioned that it can be explained by the mutual inductance between two inductor coils [78,115]. As depicted in Figure 6a, Yun et al. coupled a disk-shaped TENG directly with an inductor coil [115], pioneering a wireless communication system capable of transmitting signals over a distance of up to 60 cm. During the rotation of the disk, relative motion occurs between the triboelectric layers, generating charge separation at the contact interface, followed by periodic changes in the potential difference, which drives the TENG to produce alternating current signals. Meanwhile, these alternating current signals would induce corresponding currents in the inductor coil through electromagnetic induction, which carries the information of electrical signals generated by the TENG, and are then successfully transmitted to the inductor coil in the receiving end through inductive coupling. While this approach has achieved self-powered wireless communication for signals, the voltage signals received at the receiver end undergo rapid attenuation as the antenna distance increases.

To tackle this issue, several kinds of microswitches have been incorporated to enhance the communication range [116,117,118]. By integrating TENGs with a synchronized micro-mechanical switch in series, the high output impedance of the TENGs is markedly reduced, significantly boosting the energy coupled into the LC circuit, thereby enhancing the transmission distance. Concurrently, the varying capacitance during TENG operation does not affect the LC circuit, contributing to a more stable resonant frequency for the transmitter. As illustrated in Figure 6b, Luo’s team devised a TENG-based wireless communication system utilizing double-contact micro-mechanical switches, achieving stable signal transmission within a range of 2 m [101]. The switch closes when the triboelectric layers are at their maximum separation or contact, enabling the capture of positive and negative voltage pulses generated by TENGs. The results demonstrate that the system achieves a remarkable 73% energy conversion efficiency in the resonant coupling state, favoring extended communication ranges. Furthermore, this work delves into how the coil radius further impacts signal transmission by modulating the mutual inductance coefficient (M). It indicates that larger inductor sizes contribute to longer communication distances, yet there is always a practical pursuit of compactness and miniaturization. Thus, Luo’s group ingeniously incorporated magnetic core coils into the system without altering the original circuit architecture [102], achieving the dual benefits of reduced coil size and extended transmission distance (Figure 6c). When the diameter of the inductor coil is 1 cm, the transmission distance can be increased from 20 cm for an empty coil to 50 cm for a magnetic core coil.

Moreover, research has shown that diodes used in conjunction with micro-mechanical switches can achieve frequency enhancement through transient discharge. The coupling of diodes and micro-mechanical switches is used to neutralize the remaining induced charges on the electrodes and act as an electronic valve, which is currently one of the common strategies to improve TENG output performance [119]. As shown in Figure 6d, Luo’s group seamlessly integrated the technology into TENG-based wireless transmission circuits by embedding an L-shaped micro-mechanical switch and a diode within the TENG [103]. In this way, the output impedance of the TENG is further reduced, while the coupling between its output energy and the load is markedly enhanced, resulting in an extended transmission distance.

To overcome the limitations of traditional micro-mechanical switches in communication quality, such as noise caused by switch jitter, Luo’s group developed an electronic switch based on a MOSFET and a diode [105], resulting in exceptional stability in both signal frequency and amplitude. Figure 6e highlights that at the onset of signal transmission, high-frequency signal components lead to significantly higher noise levels, attributed to parasitic capacitance, inductance, and jittering contacts in mechanical switches—inherent to their operational mechanism. Conversely, the new MOSFET and diode-based electronic switch effectively address these noise issues, enabling swift and stable signal transmission.

Furthermore, Figure 6f depicts a different approach by a tip-discharge switch based on triboelectric plasma actuation to improve communication quality [104]. This innovative switch not only preserves the impedance-matching capabilities of conventional switches but also significantly improves the stability and smoothness of signal transmission with an astonishing response speed of 13 ns (Figure 6f). This groundbreaking design triumphs by eliminating uncontrollable air emissions during the closure of traditional mechanical switches, thereby elevating signal transmission quality to a new level. Experimental results showcase the switch’s ability to transmit signals at a frequency of once every 27 ms, while extending the communication range to 40 m, underscoring its immense potential for long-distance wireless communication applications. An additional, noteworthy distinction is that, unlike Zi’s group’s proposal which leverages high-frequency displacement currents caused by breakdown discharge to induce wireless electromagnetic signals for achieving omnidirectional transmission [98], the focus of the tip-discharge switch here is primarily on enhancing switching speed to maximize the extraction and utilization of the instantaneous output power of the TENG, ultimately bolstering the LC circuit’s capability to radiate electromagnetic waves.

It is worth mentioning that the attempt to combine optical communication technology has also brought new possibilities to the field of wireless transmission based on TENG and LC circuits. Luo’s team successfully integrated inductive coupling wireless transmission with optical communication by introducing lasers and photodetectors, further expanding the application scope of communication technology [116,120].

In summary, wireless transmission technology based on TENG and LC circuits has shown broad development prospects in the field of wireless communication due to its unique advantages. However, it cannot be ignored that in terms of breakthroughs in transmission distance and optimization of system size, this technology still contains enormous potential and vast development space, waiting for researchers to explore and implement it in depth.

4. Applications of the Self-Powered Sensing and Wireless Communication Synergic Systems Enabled by TENGs

By utilizing TENGs’ sensitivity to external stimuli, self-powered perception can be achieved. Meanwhile, high-voltage electrical signals from TENGs can be directly transmitted wirelessly through electric displacement fields or converted into electromagnetic wave signals. Consequently, under TENG activation, the sensing of external stimuli and the wireless communication modality can be carried out in an entirely self-powered manner, achieving a fully self-powered wireless sensing and communication integrated system. With the maturity of the theory and the development of the technology of self-powered sensing and wireless transmission leveraging TENGs, the self-powered sensing and wireless communication synergic systems enabled by TENGs have enabled vast critical applications in underwater systems [96,97], healthcare [121,122], smart homes [76,106], smart transportation [103,105,122], etc., demonstrating better integration, higher portability, and lower cost.

4.1. Underwater Systems

The advancement and deployment of wireless sensing and communication technologies tailored for underwater environments are of paramount importance. Considering the ocean’s status as a crucial part of our planet, which harbors a wealth of resources crying out for exploration, it inevitably necessitates a thorough exploration of the intricate underwater environment, yet the complexities of the underwater environment pose formidable challenges to effective underwater wireless transmission. The TENG-dependent self-powered wireless approach offers novel perspectives for underwater development. Diverging from conventional acoustic [123,124,125], optical [126,127], and electromagnetic field communication methods [128,129], the approach utilizing TENGs circumvents the limitations of acoustic communication’s environmental sensitivity and slow propagation, optical communication’s vulnerability to light scattering, and electromagnetic field communication’s attenuation in water due to high-frequency signals.

As shown in Figure 7a, a groundbreaking underwater wireless transmission method based on displacement current was first proposed in 2022, which mainly utilizes the electric field model and achieves wireless transmission by combining it with displacement current [96]. Due to its low excitation frequency, the embedded information can be retained to a great extent without being absorbed by the water. By modulating and demodulating the current signals generated by a sound-driven TENG connected to a transmitting electrode, texts and images can be transmitted in the water tank at a rate of 16 bits/second. Remarkably, the electrical signals are not distorted even after a transmission distance of 100 m and are virtually unaffected by salinity, turbidity, and submerged obstacles (Figure 7a). However, it is crucial to acknowledge that the TENG’s output is susceptible to humidity-induced charge dissipation, which contradicts the underwater environment [130]. Consequently, the current design necessitates the placement of the device either ashore or on a boat to avoid direct water contact, significantly restricting its practical applications. To address this limitation, Badhulika’s group designed an underwater system that can take TENGs underwater through PDMS encapsulation, effectively insulating the device from water and preserving its output performance [81]. Notably, the system not only stands out as a highly efficient underwater communication platform but also excels in underwater pulse sensing and strain monitoring of human joints, as depicted in Figure 7b. During joint motion monitoring, it becomes apparent that the signal output escalates in direct proportion to the degree of joint flexion. It also allows for the clear acquisition of human pulse signals at the receiving end, offering invaluable insights into underwater human status monitoring. Experiments have shown that encapsulation is not the only viable strategy to minimize the effect of water on the TENG output, with modifying the material and utilizing solid–liquid TENGs also proving effective. For example, Wang et al. proposed a new solid–liquid–solid TENG consisting of polytetrafluoroethylene (PTFE), water, and a graphite electrode, which harnesses the electron and ion transfer between water and the graphite electrode upon contact, converting mechanical energy from PTFE movement into electrical energy for signal transmission [109]. With this transmission system, an amplitude- and frequency-modulated Morse code strategy is developed by controlling the height between the PTFE plate and the water surface, showcasing the feasibility of self-powered wireless communication applications (Figure 7c).

Moreover, underwater systems are not confined to marine environments but also play a significant role in various liquid settings within industrial applications. Accurate measurement of complex multiphase flows is critical for facility safety and efficiency in the petroleum and chemical industries [131,132]. As shown in Figure 7d, Ma et al. developed a self-powered multiphase flow detection system combined with quantitative analysis algorithms for monitoring flow parameters in various industrial facilities such as the oil and gas industry and the nuclear industry [97]. Driven by a flowing liquid or gas, a rotating TENG generates high-frequency electrical signals sequentially emitted into the fluid by a transmitter. Through characteristic analysis of these signals, various flow parameters can be obtained, including slug frequency, slug length, and water cut. It is important to note that the group further proposed a TENG-based four-point multiphase flow sensor to detect water–air flow patterns. By arranging four receiver electrodes in the same cross-section, the fluid distribution in the radial direction is captured, enabling the precise distinction of even tiny air bubbles accompanying slug flow. The excellent performance of the system offers a promising prospect for detecting multiphase flows in large-scale flow loops of industrial facilities in remote areas.

Additionally, multifunctionality remains a challenge that requires constant breakthroughs for underwater systems. Recently, as illustrated in Figure 7e, Zhang et al. introduced a simple and fully symmetric TENG capable of efficiently harvesting omnidirectional wave energy without dead zones, thereby enabling passive underwater wireless detection over a distance of up to 220 m by leveraging the displacement current generated [100]. The high-efficiency energy conversion and ultra-long-distance communication based on the symmetric TENG lay the foundation for realizing multifunctional systems, which are equipped to simultaneously execute diverse tasks such as pipeline inspection, water level monitoring, marine navigation, and energy harvesting. Specifically, for the pipeline inspection, a transmitter and two receivers are applied. When a blockage occurs within the pipeline, the corresponding electrode fails to receive electrical signals, thereby swiftly pinpointing the blockage location. Additionally, when faced with problems arising from rapid changes in water levels due to floods and tsunamis, an acrylic board covered with a grounded aluminum film and Kapton was considered as the measured target and vertically placed in water. As the water level changes, so does the submerged area of the target, which is directly proportional to the received signal, enabling the system to effortlessly extract water level information and issue warnings when the water level reaches a specified height (e.g., 10 cm) [99]. Furthermore, the system can directly detect the size of the ship covered with grounded aluminum film and Kapton by the difference in the draft area to give navigation instructions for avoiding obstacles, which possesses the capacity for marine navigation.

As explained in the model analysis section, the high dielectric constant of the water environment offers a significant advantage for long-distance underwater communication. While underwater environments are generally considered to attenuate TENG signals, superior encapsulation techniques can address signal output limitations caused by charge dissipation. Concurrently, the underwater environment’s high compatibility with the frequency of TENG-driven wireless sensing and communication signals underscores the immense potential of this novel transmission method in underwater settings [96].

4.2. Smart Transportation

Transportation plays a pivotal role in our lives, significantly influencing economic development, social interaction, and daily routines. With the relentless march of technological advancement, the demand for monitoring traffic conditions has sharply increased, particularly in speed and traffic volume [4,133,134,135,136,137,138]. While cameras currently dominate the landscape of traffic monitoring, their reliance on external power sources poses challenges in terms of cost, installation complexity, and placement limitations [139,140]. The emergence of TENG-based wireless sensing and communication technology adeptly addresses these challenges, which can complete signal sensing and communication in a fully self-powered manner, ensuring rapid deployment in various environments, elimination of complex wiring, and monitoring from different locations at low cost. In this section, we delve into applying TENG-driven wireless sensing and communication synergic systems in land transportation.

Luo’s group devised a bicycle-speed- and tire-pressure-sensing system, comprising a TENG strategically positioned between the inner and outer tires of the bicycle, an electronic switch, a thin-film resistor, coaxial-placed inductor coil transmitter and receiver, and a liquid crystal display (LCD) terminal (Figure 8a) [105]. As the wheel rotates, the TENG comes into contact with the ground, generating electrical pulses that are converted into oscillating signals by the RLC circuit. By measuring the time interval between two consecutive received signals captured by the receiving inductor coil—essentially, the time taken for the tire to complete one revolution—the bicycle’s speed is derived using the formula v = s/t. Additionally, changes in tire pressure can cause a change in the resistance of the resistive thin-film sensor fixed between the inner and outer tire, enabling amplitude modulation of the transmitted signal. Therefore, tire pressure is inferred from the attenuation trend of this modulated signal, which intensifies as the sensor’s resistance decreases. It is worth noting that the involvement of the electronic switch not only greatly improves the energy utilization efficiency of the TENG but also avoids environmental interference, resulting in pressure measurement accuracy exceeding 97% and speed measurement accuracy far exceeding 99%. Moreover, due to the lightweight nature of the system, this component will not impose any additional burden on the rider in terms of use.

The working principle of the system can also be extended to other applications in traffic scenarios, including vehicles, railways, conveyor belts, etc. As depicted in Figure 8b, Luo’s group proposed a fully self-powered instantaneous wireless traffic monitoring system leveraging a TENG and magnetic resonance coupling, which is placed on the sidewalk to monitor illegally entered motorcycles and their driving speed and direction [103]. When a pedestrian steps on and off the TENG, a microswitch activates, prompting the TENG to generate a voltage signal that is then tuned and coupled to the receiving end through the LC circuit. While the motorcycle passes through the monitoring system, the wheels not only trigger the TENG but also act on the adjacent capacitive pressure sensor, resulting in the resonant frequency change. Therefore, high-precision identification of pedestrians or vehicles can be achieved through spectral analysis of the received signal. Beyond real-time monitoring of illegal entry of electric motorcycles into sidewalks, the system can easily obtain the flow of pedestrians and motorcycles on sidewalks by calculating the information received over a period of time and setting the frequency difference.

Moreover, TENG-driven self-powered wireless sensing and communication systems are capable of contributing significantly to atmospheric environment control by monitoring vehicle exhaust emissions. Su et al. developed an automotive exhaust detection system combining a TENG and collecting electrodes, as shown in Figure 8c [122]. During the TENG’s rotation, external mechanical motion is converted into varying displacement currents, which are then received by collecting electrodes. Cleverly, the collecting electrode here is acted upon by a resistive gas sensing unit, consisting of an acrylic substrate, a gas sensing coating, and electrodes deposited at both ends of the substrate. Due to the coupling between the TENG’s impedance matching and the resistive gas sensor’s resistance changes, target gas concentrations can be directly inferred from output voltage amplitudes. By installing a TENG on gas sensing units near the rear wheels and exhaust pipes, the concentration of NO₂ exhaust gas is automatically determined wirelessly through a wireless self-powered gas sensor array driven by tire rotation, revealing its enormous potential in air quality monitoring.

Employing simple passive components like TENGs, collector electrodes, resistors, capacitors, and inductors, the sensing and communication system offers a cost-effective alternative to expensive camera-based or power management unit-reliant systems for traffic. The TENG-based wireless sensing and transmission method, owing to its flexibility, fully self-powered operating mode, and lack of constraint by wired infrastructure, holds immense potential for ubiquitous adoption in traffic condition monitoring, ranging from traffic flow management to vehicle status checks and emission monitoring. Its innovative applications would continue to expand the boundaries of transportation monitoring, enhancing safety, efficiency, and environmental sustainability.

4.3. Other Applications in Security Systems, Human–Machine Interaction, and Healthcare

In addition to applications in underwater environments and smart transportation, TENG-based self-powered sensing and communication systems are also used in security systems, human–machine interaction, and healthcare. Nevertheless, despite their potential, the practical demonstrations of these applications remain relatively scarce and will be comprehensively summarized in this section.

TENG-based self-powered wireless sensing and communication technology has demonstrated its non-negligible advantages in security systems in certain special situations. For instance, in scenarios characterized by information obstruction, such as enclosed underground sewers, post-earthquake rubble, or hostage situations, a covert and easily implemented wireless communication plan is imperative. Tang et al. proposed a self-powered near-field wireless communication system consisting of a TENG, a transmitter, and a receiver for effective communication with external personnel [108]. When an external force is applied to the TENG positioned on one side of an obstacle, the resulting electric field is formed around the obstacle, which would be captured by the receiver located on the opposite side. Accordingly, trapped individuals can easily transmit messages wirelessly through Morse code by tapping the TENG with their hands. It is worth mentioning that when the mechanical force acts directly on the obstacle, the mechanical signals tend to be absorbed and reflected by the obstacle, drastically diminishing signal reception efficiency. The displacement current in this work solves this problem perfectly and greatly improves the signal transmission efficiency, boasting more potential applications in intelligence monitoring. Stealth is a paramount factor for detectors employed in intelligence-gathering operations, yet this capability is often constrained by the energy supply module. Remarkably, the design of this innovative work ingeniously conceals the system within decorative drawings, enabling them to gather acoustic information within a room surreptitiously. As shown in Figure 9a, acoustic vibrations within the environment would trigger the TENG, and the receiver installed at the other end of the wall can wirelessly obtain the signals. After initial signal processing and feature peak extraction, the amassed data can be subjected to advanced automatic speech recognition techniques for transcription into text, further expanding their utility and versatility.

In recent years, the TENG-based wireless human–machine interaction system has garnered significant attention, seamlessly integrating into our daily lives across various domains, including intuitive human–machine control, immersive virtual reality (VR) gaming, and smart homes [106,141,142,143,144,145,146,147,148]. Lee’s group implemented wireless trolley control using LC-tuned TENG signals [106]. By strategically deploying series–parallel textile TENGs, they harnessed the distinct resonant frequencies between pressing and releasing actions to achieve three degrees of freedom, fully satisfying the manipulation of 2D toy cars. In this case, the speed of the car was controlled by the normalized signal amplitude, and the resonance frequencies were identified to control the trajectory of the car. Furthermore, human–machine interaction systems fused with 3D VR technology enrich human experiences, offering unparalleled convenience and immersion. Nevertheless, conventional VR devices primarily relying on visual communication are often hindered by their weight and bulk, limiting user mobility and comfort. The advent of TENG-based direct wireless signal transmission offers an innovative alternative, broadening the spectrum of communication modalities available for HMI and enhancing the overall interactive experience. By strategically manipulating external circuits upon the foundation of series and parallel connections of textile TENGs, the system’s degrees of freedom are further enhanced, thus realizing a more systematic and comprehensive strategic approach to 3D VR control (such as drone control). As shown in Figure 9b, precise drone control is achieved by using adjustable capacitors (C) with capacitance ranging from 0 to 15 nanofarads (nF) to finely adjust the resonant frequency. This groundbreaking work harnesses textile TENGs for intuitive human–machine interaction, fostering seamless engagement with virtual entities. Additionally, Mallineni et al. developed a TENG-powered smart home system, depicted in Figure 9c. By simply tapping the TENG with a hand, users can effortlessly control windows, LED displays, temperature sensors, and security alarms. The whole process utilizes the strong electric field generated during the operation of the TENG for the communication of sensing signals, which can be collected only by a piece of copper tape attached to the furniture.

The use of flexible sensor devices for human health monitoring has also been a topic of great interest in recent years [149,150,151,152,153,154,155,156,157]. As shown in Figure 9d, Sun et al. developed a flexible, ultra-wideband ultrasound device based on the triboelectric effect for in vivo signal monitoring [121]. The innovative system involves an ultrasound probe transmitting continuous signals into the body and a TENG device receiving them. Subsequently, these signals are converted into electromagnetic signals by a coupling coil and transmitted wirelessly to a receiving coil positioned externally. As is known, the ultrasound velocity is related to the temperature of the medium [158,159], and thus this scheme can be applied to body temperature monitoring. As the temperature increases, the delay time between the signal acquired by the receiving coil and the input signal from the ultrasound probe decreases. Additionally, the ultrasonic velocity is also related to the physical parameters of the medium, such as Young’s modulus and density [160,161], so the change in ultrasonic velocity can also indirectly reflect the change in salt content in the body. The results show that as the salt content increases, the velocity of ultrasound in response to the received signal increases. Given TENG devices’ remarkable sensitivity to ultrasound and their proven performance in both in vivo and ex vivo wireless communication, the system holds immense potential for miniaturized implantable devices, promising significant advancements in future healthcare technologies. Additionally, the versatility of TENG-based wireless sensing and communication systems has been showcased in respiratory monitoring applications, further expanding their scope and impact [122]. As shown in Figure 9e, the integrated gas monitoring system using 3D printing can be driven by the respiratory airflow of the human body and wirelessly trigger active sensing and communication, which is consistent with the working principle described in Figure 8c, demonstrating the ability of real-time respiratory monitoring.

Overall, the TENG has shown its vast application potential across numerous fields, gaining popularity for its unparalleled convenience and promising robust prospects for future development. However, the diversity of scenarios for TENG-based wireless sensing and communication technologies still has room for continued exploration.

5. Summary and Outlook

With the development of the IoT and 5G communication technology, sensing–communication networks are experiencing explosive growth, which poses new challenges for distributed energy. Sensor devices based on TENGs have demonstrated the potential for self-powered sensing in various scenarios, owing to their simple structure and the significant advantage of not requiring a power source. Many literature reviews on self-powered sensing technology based on TENGs exist, yet a comprehensive summary of achieving self-powered wireless communication has not been well summarized. Herein, this review systematically introduces emerging self-powered wireless communication technologies triggered by TENGs and summarizes the applications of self-powered sensing and wireless communication synergic systems in different fields. Starting from the primary mechanism of TENGs, this review elaborately analyzes the basic models of using TENGs to achieve self-powered wireless communication, i.e., using the electric displacement field and triggered electromagnetic waves during TENG operation to achieve self-powered wireless communication. These communication technologies exhibit different characteristics in terms of device structure, circuit design, signal characteristics, and communication distance. By further combining self-powered sensing technology, the potential applications of these self-powered sensing and wireless communication synergic systems in different domains are explored, such as underwater systems, smart transportation, personal healthcare, etc. Different from the traditional distributed energy sources such as batteries or cables, these systems eliminate the disadvantage of frequent battery replacement and demonstrate tremendous advantages in portability. Compared with the well-established self-powered wireless sensing and communication systems that only use TENGs as the power supply, these systems do not require complex energy management circuits, further simplifying the circuit design and complexity at the sensor end. Overall, the fully self-powered sensing and wireless communication synergic systems achieve the complete cycle of external stimulus perception, signal modulation, and wireless transmission without the requirement for power and external cables, offering significant application potential in a broader range of scenarios, especially in harsh environments like deep-sea operations and systems with significant constraints like implantable applications.

With the continuous optimization of device structures and circuit systems, a large amount of work has provided feasible solutions for implementing self-powered sensing and wireless communication technology based on TENGs. By leveraging the sensitivity of TENGs to external stimuli, they can function as self-powered sensors to enable information perception. Meanwhile, the electric displacement field or electromagnetic waves generated by TENGs under stimulation are ingeniously utilized to achieve wireless transmission of information. This feature facilitates the seamless integration of self-powered sensing technology with wireless communication systems, jointly forming an efficient and self-sufficient solution for information sensing and communication. However, there are still some challenges in achieving precise signal perception and wireless long-distance lossless communication (Figure 10).

Firstly, numerous research works showed that the electric displacement field and modulated electromagnetic waves generally decrease with increasing distance. Notably, for applications in air media, the ability for long-distance wireless transmission still needs to be significantly improved. One optional direction is to improve the energy conversion efficiency of TENGs further. For example, designing new materials with high dielectric constant and specific surface area offers desirable benefits in TENGs’ high energy harvesting capacity. Additionally, the optimization design of symmetric or composite structures is also one of the possible options to consider.

Secondly, existing long-distance communication is often applied to single-signal transmission, and continuous signal perception and communication remain a significant challenge. However, continuous monitoring of external stimuli is paramount in practical applications, underscoring the urgency of intensifying research into long-range, continuous sensing and communication. Notably, existing systems reliant on electric displacement fields or modulated electromagnetic waves often necessitate kilovolt-level TENG signals for effective long-range communication, inadvertently limiting the detection of minute signals. Therefore, there is an urgent need to propose a scalable solution for small signals and continuous sensing and communication.

Thirdly, existing research often overlooks the impact of external interference sources on the stability of TENG operation, which would affect the quality of sensing and communication. In more practical application scenarios, further research on device packaging and signal transmission path selection is essential to enhance system compatibility and robustness. Moreover, introducing more advanced signal processing algorithms may be a potential solution to enhance the communication quality. Additionally, system integration and miniaturization are essential for modern technology to achieve high efficiency, portability, and sustainable development. In TENG-based wireless systems, developing modular and miniaturized sensor communication systems would further improve the system’s applicability and reliability in various scenarios.

Finally, the self-powered sensing and wireless communication synergic system triggered by TENGs has demonstrated remarkable application prospects in multiple fields, such as smart transportation, underwater applications, safety protection systems, human–machine interaction, and healthcare, which boast unique advantages in energy autonomy, minimized maintenance costs, and enhanced reliability. Nevertheless, despite their promising potential, actual demonstrations in practical situations remain relatively scarce. Further research endeavors in diverse applications and practical implementations are imperative to uncover the untapped potential of these systems in real-world applications, thereby better empowering self-powered sensing and communication technologies for IoT. Concurrently, intensified explorations of applications to gain insights into their real-world performance and limitations would in turn promote further enhancement and widespread adoption of self-powered systems.

In summary, utilizing TENGs to achieve self-powered wireless sensing and communication has demonstrated significant advantages, including a fully self-powered working mode, real-time signal sensing and wireless communication, streamlined structural design, and lower costs. The self-powered sensing and wireless communication synergic technology based on TENGs’ electric displacement field and/or tuned electromagnetic wave signals has opened up new possibilities for the rapid development of IoT sensor nodes and systems.