Editorial

70 KiB

Open AccessEditorial

by Wei-Chih Wang

Sensors 2014, 14(8), 15065-15066; https://doi.org/10.3390/s140815065 - 15 Aug 2014

Cited by 2 | Viewed by 4526

Sensors and actuators using polymeric systems, constitute one of the most promising fields of “smart polymers”, and it is becoming ever more important to associate artificial sensing and actuating systems with living organisms. [...] Full article

(This article belongs to the Special Issue Polymeric Micro Sensors and Actuators)

Research

Jump to: Editorial, Review, Other

844 KiB

Open AccessArticle

Sensitivity of Pressure Sensors Enhanced by Doping Silver Nanowires

by Baozhang Li, Chengyi Xu, Jianming Zheng and Chunye Xu

Sensors 2014, 14(6), 9889-9899; https://doi.org/10.3390/s140609889 - 04 Jun 2014

Cited by 61 | Viewed by 8591

Abstract

We have developed a highly sensitive flexible pressure sensor based on a piezopolymer and silver nanowires (AgNWs) composite. The composite nanofiber webs are made by electrospinning mixed solutions of poly(inylidene fluoride) (PVDF) and Ag NWs in a cosolvent mixture of dimethyl formamide and [...] Read more.

We have developed a highly sensitive flexible pressure sensor based on a piezopolymer and silver nanowires (AgNWs) composite. The composite nanofiber webs are made by electrospinning mixed solutions of poly(inylidene fluoride) (PVDF) and Ag NWs in a cosolvent mixture of dimethyl formamide and acetone. The diameter of the fibers ranges from 200 nm to 500 nm, as demonstrated by SEM images. FTIR and XRD results reveal that doping Ag NWs into PVDF greatly enhances the content of β phase in PVDF. This β phase increase can be attributed to interactions between the Ag NWs and the PVDF matrix, which forces the polymer chains to be embedded into the β phase crystalline. The sensitivity of the pressure sensors agrees well with the FTIR and XRD characteristics. In our experiments, the measured sensitivity reached up to 30 pC/N for the nanofiber webs containing 1.5 wt% Ag NWs, which is close to that of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE), (77/23)]. This study may provide a new method of fabricating high performance flexible sensors at relatively low cost compared with sensors based on [P(VDF-TrFE), (77/23)]. Full article

(This article belongs to the Special Issue Polymeric Micro Sensors and Actuators)

► Show Figures

689 KiB

Open AccessArticle

A CMOS Humidity Sensor for Passive RFID Sensing Applications

by Fangming Deng, Yigang He, Chaolong Zhang and Wei Feng

Sensors 2014, 14(5), 8728-8739; https://doi.org/10.3390/s140508728 - 16 May 2014

Cited by 30 | Viewed by 8021 | Correction

Abstract

This paper presents a low-cost low-power CMOS humidity sensor for passive RFID sensing applications. The humidity sensing element is implemented in standard CMOS technology without any further post-processing, which results in low fabrication costs. The interface of this humidity sensor employs a PLL-based [...] Read more.

This paper presents a low-cost low-power CMOS humidity sensor for passive RFID sensing applications. The humidity sensing element is implemented in standard CMOS technology without any further post-processing, which results in low fabrication costs. The interface of this humidity sensor employs a PLL-based architecture transferring sensor signal processing from the voltage domain to the frequency domain. Therefore this architecture allows the use of a fully digital circuit, which can operate on ultra-low supply voltage and thus achieves low-power consumption. The proposed humidity sensor has been fabricated in the TSMC 0.18 μm CMOS process. The measurements show this humidity sensor exhibits excellent linearity and stability within the relative humidity range. The sensor interface circuit consumes only 1.05 µW at 0.5 V supply voltage and reduces it at least by an order of magnitude compared to previous designs. Full article

(This article belongs to the Special Issue Polymeric Micro Sensors and Actuators)

► Show Figures

855 KiB

Open AccessArticle

Fabrication and Characterization of a Micromachined Swirl-Shaped Ionic Polymer Metal Composite Actuator with Electrodes Exhibiting Asymmetric Resistance

by Guo-Hua Feng and Kim-Min Liu

Sensors 2014, 14(5), 8380-8397; https://doi.org/10.3390/s140508380 - 12 May 2014

Cited by 17 | Viewed by 6619

Abstract

This paper presents a swirl-shaped microfeatured ionic polymer-metal composite (IPMC) actuator. A novel micromachining process was developed to fabricate an array of IPMC actuators on a glass substrate and to ensure that no shortcircuits occur between the electrodes of the actuator. We demonstrated [...] Read more.

This paper presents a swirl-shaped microfeatured ionic polymer-metal composite (IPMC) actuator. A novel micromachining process was developed to fabricate an array of IPMC actuators on a glass substrate and to ensure that no shortcircuits occur between the electrodes of the actuator. We demonstrated a microfluidic scheme in which surface tension was used to construct swirl-shaped planar IPMC devices of microfeature size and investigated the flow velocity of Nafion solutions, which formed the backbone polymer of the actuator, within the microchannel. The unique fabrication process yielded top and bottom electrodes that exhibited asymmetric surface resistance. A tool for measuring surface resistance was developed and used to characterize the resistances of the electrodes for the fabricated IPMC device. The actuator, which featured asymmetric electrode resistance, caused a nonzero-bias current when the device was driven using a zero-bias square wave, and we propose a circuit model to describe this phenomenon. Moreover, we discovered and characterized a bending and rotating motion when the IPMC actuator was driven using a square wave. We observed a strain rate of 14.6% and a displacement of 700 μm in the direction perpendicular to the electrode surfaces during 4.5-V actuation. Full article

(This article belongs to the Special Issue Polymeric Micro Sensors and Actuators)

► Show Figures

Graphical abstract

494 KiB

Open AccessArticle

Novel Piezoelectric Effect and Surface Plasmon Resonance-Based Elements for MEMS Applications

by Sigita Ponelyte and Arvydas Palevicius

Sensors 2014, 14(4), 6910-6921; https://doi.org/10.3390/s140406910 - 17 Apr 2014

Cited by 9 | Viewed by 7452

Abstract

This paper covers research on novel thin films with periodical microstructure—optical elements, exhibiting a combination of piezoelectric and surface plasmon resonance effects. The research results showed that incorporation of Ag nanoparticles in novel piezoelectric—plasmonic elements shift a dominating peak in the visible light [...] Read more.

This paper covers research on novel thin films with periodical microstructure—optical elements, exhibiting a combination of piezoelectric and surface plasmon resonance effects. The research results showed that incorporation of Ag nanoparticles in novel piezoelectric—plasmonic elements shift a dominating peak in the visible light spectrum. This optical window is essential in the design of optical elements for sensing systems. Novel optical elements can be tunable under defined bias and change its main grating parameters (depth and width) influencing the response of diffraction efficiencies. These elements allow opening new avenues in the design of more sensitive and multifunctional microdevices. Full article

(This article belongs to the Special Issue Polymeric Micro Sensors and Actuators)

► Show Figures

804 KiB

Open AccessArticle

Autonomous Oscillation of Polymer Chains Induced by the Belousov–Zhabotinsky Reaction

by Yusuke Hara and Yoshiko Takenaka

Sensors 2014, 14(1), 1497-1510; https://doi.org/10.3390/s140101497 - 15 Jan 2014

Cited by 10 | Viewed by 6416

Abstract

We investigated the self-oscillating behaviors of two types of polymer chains induced by the Belousov–Zhabotinsky (BZ) reaction. One consisted of N-isopropylacrylamide (NIPAAm) and the Ru catalyst of the BZ reaction, and the other consisted of NIPAAm, the Ru catalyst, and acrylamide-2-methylpropanesulfonic acid [...] Read more.

We investigated the self-oscillating behaviors of two types of polymer chains induced by the Belousov–Zhabotinsky (BZ) reaction. One consisted of N-isopropylacrylamide (NIPAAm) and the Ru catalyst of the BZ reaction, and the other consisted of NIPAAm, the Ru catalyst, and acrylamide-2-methylpropanesulfonic acid (AMPS) with a negatively charged domain as a solubility control site. A comparison of the two types of self-oscillation systems showed that the anionic AMPS portion of the polymer chain significantly affected the self-oscillating behavior under strongly acidic condition. The periods of self-oscillation for the two types of self-oscillating polymer chains were investigated by changing the initial concentrations of the three BZ substrates and the temperature. As a result, it was demonstrated that the period of self-oscillation could be controlled by the concentration of the BZ substrates and the temperature. Furthermore, the activation energies of the two types of the self-oscillating polymer chains gave similar values as normal BZ reactions, i.e., not including the self-oscillating polymer system with a Ru moiety. In addition, it was clarified the activation energy was hardly affected by the initial concentration of the three BZ substrates. Full article

(This article belongs to the Special Issue Polymeric Micro Sensors and Actuators)

► Show Figures

1038 KiB

Open AccessArticle

Development of a Multi-Channel Piezoelectric Acoustic Sensor Based on an Artificial Basilar Membrane

by Youngdo Jung, Jun-Hyuk Kwak, Young Hwa Lee, Wan Doo Kim and Shin Hur

Sensors 2014, 14(1), 117-128; https://doi.org/10.3390/s140100117 - 20 Dec 2013

Cited by 34 | Viewed by 9666

Abstract

In this research, we have developed a multi-channel piezoelectric acoustic sensor (McPAS) that mimics the function of the natural basilar membrane capable of separating incoming acoustic signals mechanically by their frequency and generating corresponding electrical signals. The McPAS operates without an external energy [...] Read more.

In this research, we have developed a multi-channel piezoelectric acoustic sensor (McPAS) that mimics the function of the natural basilar membrane capable of separating incoming acoustic signals mechanically by their frequency and generating corresponding electrical signals. The McPAS operates without an external energy source and signal processing unit with a vibrating piezoelectric thin film membrane. The shape of the vibrating membrane was chosen to be trapezoidal such that different locations of membrane have different local resonance frequencies. The length of the membrane is 28 mm and the width of the membrane varies from 1 mm to 8 mm. Multiphysics finite element analysis (FEA) was carried out to predict and design the mechanical behaviors and piezoelectric response of the McPAS model. The designed McPAS was fabricated with a MEMS fabrication process based on the simulated results. The fabricated device was tested with a mouth simulator to measure its mechanical and piezoelectrical frequency response with a laser Doppler vibrometer and acoustic signal analyzer. The experimental results show that the as fabricated McPAS can successfully separate incoming acoustic signals within the 2.5 kHz–13.5 kHz range and the maximum electrical signal output upon acoustic signal input of 94 dBSPL was 6.33 mVpp. The performance of the fabricated McPAS coincided well with the designed parameters. Full article

(This article belongs to the Special Issue Polymeric Micro Sensors and Actuators)

► Show Figures

918 KiB

Open AccessArticle

Optimal Design of a Polyaniline-Coated Surface Acoustic Wave Based Humidity Sensor

by Wen Wang, Xiao Xie and Shitang He

Sensors 2013, 13(12), 16816-16828; https://doi.org/10.3390/s131216816 - 05 Dec 2013

Cited by 17 | Viewed by 8187

Abstract

This paper presents an optimal design for a new humidity sensor composed of a dual-resonator oscillator configuration with an operation frequency of 300 MHz, and a polyaniline (PANI) coating deposited along the resonation cavity of the sensing device. To improve the corrosion resistance [...] Read more.

This paper presents an optimal design for a new humidity sensor composed of a dual-resonator oscillator configuration with an operation frequency of 300 MHz, and a polyaniline (PANI) coating deposited along the resonation cavity of the sensing device. To improve the corrosion resistance of the sensor chip, Al/Au electrodes were used to form the SAW resonator. Prior to device fabrication, the coupling of modes (COM) model was used for the performance prediction and optimal design parameters determination. Two SAW resonators with Al/Au electrodes were fabricated on an ST-X quartz substrate, and used as the frequency control element in the feedback path of an oscillator circuit. A PANI thin coating was deposited onto the resonator cavity of the sensing device by a spinning approach as the sensor material for relative humidity (RH) detection. High detection sensitivity, quick response, good repeatability and stability were observed from the sensor experiments at room temperature. Full article

(This article belongs to the Special Issue Polymeric Micro Sensors and Actuators)

► Show Figures

Review

Jump to: Editorial, Research, Other

1279 KiB

Open AccessReview

Flexible Carbon Nanotube Films for High Performance Strain Sensors

by Olfa Kanoun, Christian Müller, Abderahmane Benchirouf, Abdulkadir Sanli, Trong Nghia Dinh, Ammar Al-Hamry, Lei Bu, Carina Gerlach and Ayda Bouhamed

Sensors 2014, 14(6), 10042-10071; https://doi.org/10.3390/s140610042 - 06 Jun 2014

Cited by 251 | Viewed by 19952

Abstract

Compared with traditional conductive fillers, carbon nanotubes (CNTs) have unique advantages, i.e., excellent mechanical properties, high electrical conductivity and thermal stability. Nanocomposites as piezoresistive films provide an interesting approach for the realization of large area strain sensors with high sensitivity and low [...] Read more.

Compared with traditional conductive fillers, carbon nanotubes (CNTs) have unique advantages, i.e., excellent mechanical properties, high electrical conductivity and thermal stability. Nanocomposites as piezoresistive films provide an interesting approach for the realization of large area strain sensors with high sensitivity and low manufacturing costs. A polymer-based nanocomposite with carbon nanomaterials as conductive filler can be deposited on a flexible substrate of choice and this leads to mechanically flexible layers. Such sensors allow the strain measurement for both integral measurement on a certain surface and local measurement at a certain position depending on the sensor geometry. Strain sensors based on carbon nanostructures can overcome several limitations of conventional strain sensors, e.g., sensitivity, adjustable measurement range and integral measurement on big surfaces. The novel technology allows realizing strain sensors which can be easily integrated even as buried layers in material systems. In this review paper, we discuss the dependence of strain sensitivity on different experimental parameters such as composition of the carbon nanomaterial/polymer layer, type of polymer, fabrication process and processing parameters. The insights about the relationship between film parameters and electromechanical properties can be used to improve the design and fabrication of CNT strain sensors. Full article

(This article belongs to the Special Issue Polymeric Micro Sensors and Actuators)

► Show Figures

1011 KiB

Open AccessReview

Poly (N-isopropylacrylamide) Microgel-Based Optical Devices for Sensing and Biosensing

by Molla R. Islam, Andrews Ahiabu, Xue Li and Michael J. Serpe

Sensors 2014, 14(5), 8984-8995; https://doi.org/10.3390/s140508984 - 21 May 2014

Cited by 96 | Viewed by 10675

Abstract

Responsive polymer-based materials have found numerous applications due to their ease of synthesis and the variety of stimuli that they can be made responsive to. In this review, we highlight the group’s efforts utilizing thermoresponsive poly (N-isopropylacrylamide) (pNIPAm) microgel-based optical devices [...] Read more.

Responsive polymer-based materials have found numerous applications due to their ease of synthesis and the variety of stimuli that they can be made responsive to. In this review, we highlight the group’s efforts utilizing thermoresponsive poly (N-isopropylacrylamide) (pNIPAm) microgel-based optical devices for various sensing and biosensing applications. Full article

(This article belongs to the Special Issue Polymeric Micro Sensors and Actuators)

► Show Figures