Search Results (137)

A novel stretchable flexible electrode capable of simultaneously detecting isotropic three-directional strain and normal pressure has been developed. Inspired by the recursive symmetry of the Peano-Gosper fractal, the electrode integrates liquid metal (EGaIn) microchannels within a PDMS matrix to achieve uniform strain distribution and mechanically robust conductive pathways under large deformation. Within a strain range of 0–60%, the electrode exhibits highly consistent three-directional responses, with resistance variation across axes kept below 4% and a gauge factor (GF) standard deviation of only 0.0252. The device demonstrates low hysteresis (minimum DH = 0.94%), good cyclic durability, and reliable electromechanical stability. For normal pressure sensing (0–20 kPa), it provides a linear response (R² ≈ 0.99) with a moderate sensitivity of 0.198 kPa⁻¹. Wearable tests on the wrist, finger, and fingertip confirm the electrode’s reliable operation in multidimensional mechanical monitoring. This integrated fractal–liquid metal design offers a promising route for multifunctional sensing in applications such as soft robotics, human–machine interaction, and wearable electronics. Full article

Soft electrothermal actuators have attracted increasing attention in soft robotics and wearable systems due to their simple structure, low driving voltage, and ease of integration. However, traditional designs based on homogeneous or layered composites often suffer from interfacial failure and limited deformation modes, restricting their long-term stability and actuation versatility. In this study, we present a programmable soft electrothermal actuator based on a functionally graded structure composed of polydimethylsiloxane (PDMS)/multiwalled carbon nanotube (MWCNTs) composite material and an embedded EGaIn conductive circuit. Rheological and mechanical characterization confirms the enhancement of viscosity, modulus, and tensile strength with increasing MWCNTs content, confirming that the gradient structure improves mechanical performance. The device shows excellent actuation performance (bending angle up to 117°), fast response (8 s), and durability (100 cycles). The actuator achieves L-shaped, U-shaped, and V-shaped bending deformations through circuit pattern design, demonstrating precise programmability and reconfigurability. This work provides a new strategy for realizing programmable, multimodal deformation in soft systems and offers promising applications in adaptive robotics, smart devices, and human–machine interfaces. Full article

This study investigates the mechanical and tribological behavior of a polydimethylsiloxane (PDMS)–silica nanocomposite coating over the temperature range extending from 24 °C to 120 °C. Nanoindentation tests revealed depth- and temperature-dependent variations in hardness and complex modulus. A time-dependent deformation model accurately captured the viscoelastic and viscoplastic behavior observed during sustained loading, providing predictive insight into the coating’s thermomechanical performance. Tribological evaluation through friction and nanoscratch testing demonstrated a temperature-induced increase in the coefficient of friction. The integration of mechanical and surface metrology and characterization techniques offers a comprehensive understanding of the coating’s behavior under thermal and mechanical stress. These findings support the design of robust nanocomposite coatings with superior functional performance for practical applications requiring enhanced mechanical stability, wear resistance, and thermal tolerance in challenging service environments. Full article

For meeting the growing demand for lightweight impact-resistant materials, this study designed and fabricated a carbon hollow microsphere (CHM)-reinforced polydimethylsiloxane (PDMS) composite and systematically investigated the influence of CHM packing structure on its energy absorption performance. Through optimizing the controllable preparation processes of the CHMs, CHMs with low breaking rates and novel structural stability were successfully prepared. A vacuum-assisted mixing–casting method was employed to synthesize the CHM/PDMS composites with varying CHM contents (0~10 wt.%). The results demonstrated that the incorporation of CHMs significantly enhanced the compressive strength, compressive modulus, and energy absorption efficiency of the PDMS matrix. Under quasi-static loading, the composite with 4 wt.% CHM exhibited optimal comprehensive performance, achieving a 124.68% increase in compressive strength compared to pure PDMS. In dynamic impact tests, the compressive strength and energy absorption at a strain rate of 4500 s⁻¹ increased by 1245.09% and 1218.32%, respectively. The improvement of mechanical properties can be mainly attributed to the introduction of CHMs with an appropriate percentage, which can form a dense stacking structure so that the interaction force between the CHMs and PDMS matrix can be improved through the dense stacking effect, and the external force can be effectively dissipated through interface interaction, in addition to the energy dissipated by the deformation of the matrix deformation and crush of the CHMs. Additionally, the introduction of CHMs elevated the onset thermal decomposition temperature of the materials, leading to an enhanced thermal stability of the CHM/PDMS composite compared to that of the pure PDMS. Overall, this study provides theoretical and experimental foundations for designing lightweight impact-resistant materials and demonstrates the potential of CHM/PDMS composites for multifunctional safety protection. Full article

Developing stretchable strain sensors that combine both high sensitivity and a wide linear range is a critical requirement for health electronics, yet it remains challenging to meet the practical demands of daily health monitoring. This study proposes a novel heterogeneous surface strategy by in situ silver deposition on modified PDMS followed by MXene spray coating, constructing a multilevel microcrack strain sensor (MAP) using silver nanoparticles and MXene. This innovative multilevel heterogeneous microcrack structure forms a dual conductive network, which demonstrates excellent detection performance within GF_max = 487.3 and response time ≈65 ms across various deformation variables. And the seamless integration of the sensor arrays was designed and employed for the detection of human activities without sacrificing biocompatibility and comfort. Furthermore, by adopting advanced deep learning technology, these sensor arrays could identify different joint movements with an accuracy of up to 95%. These results provide a promising example for designing high-performance stretchable strain sensors and intelligent recognition systems. Full article

The poor interfacial adhesion between ductile gold (Au) electrodes and polydimethylsiloxane (PDMS) substrates affects their application in flexible sensors. Here, a porous Au electrode is designed and combined with a flexible PDMS substrate to form a structure that embeds Au into the PDMS film, thereby enhancing the interfacial adhesion of the Au/PDMS electrode. The resistivity change of the Au/PDMS electrode is only 12.3% after 100 tape peeling trials. The resistance of the Au/PDMS electrode remains stable at the 30% strain level after 2000 tensile cycling tests. This feature is mainly attributed to the deformation buffering effect of the porous Au film. After 100 min of ultrasonic oscillation testing, the resistivity change of the Au/PDMS electrode remains stable. It is also shown that the Au/PDMS electrode has excellent interfacial adhesion properties, which is mainly attributed to the interlocking effect of the Au/PDMS electrode structure. In addition, the temperature coefficient of resistance (TCR) of the temperature sensor based on the Au/PDMS electrode is approximately 0.00320/°C and the sensor’s sensitivity remains almost stable after 200 temperature measurement cycles. Au/PDMS electrodes have great potential for a wide range of applications in flexible electronics due to their excellent interfacial adhesion and electrical stability. Full article

This study investigates the elevated-temperature mechanical and viscoelastic properties of a PDMS–silica-based superhydrophobic nanocomposite coating using nanoindentation and a nano-dynamic mechanical analysis over a temperature range of 24 °C to 160 °C. The nanoindentation load–displacement curves exhibited consistent hysteresis, indicating a stable energy dissipation across the temperature range. Creep tests revealed an increased displacement and accelerated deformation at elevated temperatures, displaying a two-stage creep profile characterized by rapid primary and steady-state secondary creep. The hardness decreased with the creep time, while the strain rate sensitivity remained relatively stable, suggesting consistent deformation mechanisms. A time-dependent creep model incorporating linear and logarithmic terms accurately captured the experimental data. The nano-dynamic mechanical analysis results showed a decrease in the storage modulus with depth, while the loss modulus and tan δ peaked at shallow depths. These findings are crucial for the evaluation and design of superhydrophobic nanocomposite coatings. Full article

This study investigated the effect of adding polydimethylsiloxane (PDMS) on the processing, surface and mechanical properties of linear low-density polyethylene (rLLDPE) recyclate generated as post-production waste in the rotational molding process. Polymer blends containing 0.1, 0.2, 0.4, 1.0 and 2.0 wt.% of polydimethylsiloxane were produced during twin-screw extrusion, followed by cold granulation. The addition of the modifier at the adopted concentration range lowered the water absorption of the recyclate and contributed to a slight increase in processing shrinkage; however, it did not significantly affect its processability (MFR~const). The modification carried out increased the hydrophobic character of the recyclate surface (the wetting angle for water was enhanced) and decreased the value of the dynamic friction coefficient. It also contributed to an improvement in surface gloss. The deterioration of point hardness and scratch hardness of the recyclate was noted with an increase in the PDMS content in the mixture. The addition of polydimethylsiloxane caused changes in the nature of resulting cracks (increased width and reduced longitudinal deformation), which led to surface smoothing and increased the sliding effects. There was no negative effect of PDMS addition on the mechanical properties (static tensile) of the recyclate. The impact strength of rLLDPE deteriorated slightly. The research conducted shows the high application potential of PDMS as a modifier of the surface properties of low-density polyethylene linear recyclate and of selected processing properties, which can contribute to the shortening of the production cycle, thus potentially increasing its attractiveness compared to the original raw materials. Full article

In the rapidly advancing era of intelligent technology, flexible strain sensors are emerging as a key component in wearable electronics. Laser-induced graphene (LIG) stands out as a promising fabrication method due to its rapid processing, environmental sustainability, low cost, and superior physicochemical properties. However, the stretchability and conformability of LIG are often limited by the substrate material, hindering its application in scenarios requiring high deformation. To address this issue, we propose a high-performance flexible and stretchable strain sensor fabricated by generating graphene on a polyimide (PI) substrate using laser induction and subsequently transferred onto a polydimethylsiloxane (PDMS). The resultant sensor demonstrates an ultra-low detection limit (0.1%), a rapid response time (150 ms), a wide strain range (40%), and retains stable performance after 1000 stretching cycles. Notably, this sensor has been successfully applied to the real-time monitoring of civil aviation test pilots during flight for the first time, enabling the accurate detection of physiological signals such as pulse, hand movements, and blink frequency. This study introduces a unique and innovative solution for the real-time health monitoring of civil aviation test pilots, with significant implications for enhancing flight safety. Full article

Flexible piezoresistive pressure sensors have great potential in wearable electronics due to their simple structure, low cost, and ease of fabrication. Porous polymer materials, with their highly deformable internal pores, effectively expand the sensing range. However, a single-sized pore structure struggles to achieve both high sensitivity and a broad sensing range simultaneously. In this study, a PDMS-based flexible pressure sensor with a bilayer porous structure (BLPS) was successfully fabricated using clamping compression and a sacrificial template method with spherical sucrose cores. The resulting sensor exhibits highly uniform pore sizes, thereby improving performance consistency. Furthermore, since different pore sizes and thicknesses correspond to varying Young’s moduli, this study achieves tunable sensitivity across a wide pressure range by adjusting the bilayer thickness ratio (maximum sensitivity of $0.063 {\mathrm{kPa}}^{-1}$ in the 0–23.6 kPa range, with a pressure response range of 0–654 kPa). The sensor also demonstrates a fast response time (128 ms) and excellent fatigue stability (>10,000 cycles). Additionally, this sensor holds great application potential for facial expression monitoring, joint motion detection, pressure distribution matrices, and Morse code communication. Full article

Flexible actuators hold significant promise for applications in intelligent robotics, wearable devices, and biomimetic systems. However, conventional actuators face challenges such as high driving voltages, inadequate deformation control, and limited deformation modes, which hinder complex programmable dynamic deformations. This study presents an electrothermal actuator based on a conductive silver paste/Kapton/PDMS composite structure, enabling precise and adjustable deformation through programmable thermal control. Experimental results show that the actuator achieves a large-angle bending (∼203°) within 12 s under a low driving voltage of 2.0 V. Compared to the PTFE/MXene/PI structure, the proposed actuator achieves a 64% increase in bending angle, a 70% reduction in response time, and a 67% decrease in driving voltage. By independently controlling multiple heating elements, the actuator exhibits programmable deformation modes, including local, symmetric, and sinusoidal bending. The relationship between input voltage and deformation amplitude is described using a sinusoidal function model, experimentally validated for accuracy. Compared to traditional actuators, the proposed design offers significant improvements in bending angle, response speed, and voltage requirements. By optimizing the conductive silver paste pattern and voltage input strategy, this work develops a low-voltage, highly controllable, multi-mode programmable actuator with potential for applications in flexible robotics and space-deformable antennas. Full article

The current deformation scheme used in the 4D printing of ceramics has several disadvantages, such as a poor deformation capacity, high process complexity, and the poor mechanical properties of the product. In order to solve these problems, the deformation scheme introduced in this study utilizes the pyrolytic expansion of polyurethane and the resulting pores to hinder the contraction of the specimen during the ceramization stage. Then, the specimen is composited with a polyurethane-free portion that has a high rate of shrinkage, and deformation is initiated through the interlayer stress mismatch generated by the difference in the shrinkage of the different layers, thus enabling the preparation of complex structural ceramics. This solution is simple and efficient; heat treatment is performed in a single pass, and the precursor specimen is highly deformable. The incorporation capacity of the aluminum oxide ceramic powder was increased by replacing part of the Dow Corning SE 1700 polydimethylsiloxane silicone rubber in the raw material with Dow Corning DC 184 polydimethylsiloxane silicone rubber, which, in turn, improved the mechanical properties of the obtained ceramics by enhancing the solid-phase content of the ceramic powder. Due to the introduction of polyurethane, the ceramic has a secondary pore structure, which has the potential for application in the field of engineering materials and heat insulation materials. Full article

This study explores the rheological properties of polydimethylsiloxane (PDMS) composites with glass beads (GBs) to replicate the compression-stiffening behavior of biological tissues. The mechanical properties of soft tissues arise from interactions between the extracellular matrix (ECM) and embedded cells. To mimic this, PDMS was used as a polymeric matrix, while rigid GBs acted as non-deformable inclusions facilitating stress redistribution. PDMS composites with 10%, 20%, and 30% GB concentrations were fabricated. Rheological analysis revealed that GBs significantly enhanced the storage modulus (G′), with stiffness increasing linearly under compression. The stiffening rate rose from 300 Pa/% (pure PDMS) to 387 Pa/%, 836 Pa/%, and 2035 Pa/% for 10%, 20%, and 30% GB, respectively, marking a sevenfold increase at the highest concentration. Similarly, the apparent Young’s modulus increased from 150 kPa (pure PDMS) to 200 kPa, 300 kPa, and 380 kPa for composites with 10%, 20%, and 30% GB, respectively. PDMS-GB composites successfully reproduce the compression-stiffening effect observed in biological tissues, which may aid research in mechanobiology and tissue engineering. Full article

Since the introduction of polydimethylsiloxane (PDMS) microfluidic devices at the beginning of the 21st century, this elastomeric polymer has gained significant attention in the engineering community due to its biocompatibility, exceptional mechanical and optical properties, thermal stability, and versatility. PDMS has been widely used for in vitro experiments ranging from the macro- to nanoscale, enabling advances in blood flow studies, biomodels improvement, and numerical validations. PDMS devices, including microfluidic systems, have been employed to investigate different kinds of fluids and flow phenomena such as in vitro blood flow, blood analogues, the deformation of individual cells and the cell free layer (CFL). The most recent applications of PDMS involve complex hemodynamic studies such as flow in aneurysms and in organ-on-a-chip (OoC) platforms. Furthermore, the distinctive properties of PDMS, including optical transparency, thermal stability, and versality have inspired innovative applications beyond biomedical applications, such as the development of transparent, virus-protective face masks, including those for SARS-CoV-2 and serpentine heat exchangers to enhance heat transfer and energy efficiency in different kinds of thermal systems. This review provides a comprehensive overview of the current research performed with PDMS and outlines some future directions, in particular applications of PDMS in engineering, including biomicrofluidics, in vitro biomodels, heat transfer, and face masks. Additionally, challenges related to PDMS hydrophobicity, molecule absorption, and long-term stability are discussed alongside the solutions proposed in the most recent research studies. Full article

Flexible sensing materials have become a hot topic due to their sensitive electrical response to external force or temperature and their promising applications in flexible wear and human–machine interaction. In this study, a PDMS/capillary GaInSn flexible sensing material with high force and thermal sensitivity was prepared utilizing liquid metal (LM, GaInSn), flexible silicone capillary, and polydimethylsiloxane (PDMS). The resistance (R) of the flexible sensing materials under the action of different forces and temperatures was recorded in real-time. The electrical performance results confirmed that the R of the sensing material was responsive to temperature changes and increased with the increasing temperature, indicating its ability to transmit temperature signals into electrical signals. The R was also sensitive to the external force, such as cyclic stretching, cyclic compression, cyclic bending, impact and rolling. The ΔR/R₀ changed periodically and stably with the cyclic stretching, cyclic compression and cyclic bending when the conductive pathway diameter was 0.5–1.0 mm, the cyclic tensile strain ≤ 20%, the cyclic tensile rate ≤ 2.0 mm/min, the compression ratio ≤ 0.5, and the relative bending curvature ≤ 0.16. Moreover, the material exhibited sensitivity in detecting biological signals, such as the joint movements of the finger, wrist, elbow and the stand up-crouch motion. In conclusion, this work provides a method for preparing a sensing material with the capillary structure, which was confirmed to be sensitive to force and heat, and it produced different types of R signals under different deformations and different temperatures. Full article