Polymer Diaphragm Research Articles

ЭЛЕКТРОЛИЗ РАСТВОРА БРОМИСТО-БРОМНОГО ЖЕЛЕЗА В ЭЛЕКТРОЛИЗЕРЕ ЗАКРЫТОГО ТИПА

In order to optimize the electrolysis process of iron bromide solution, a sealed design of the electro-lyzer has been developed, which will reduce the removal of bromine into the atmosphere. The effect of the concentration of a bromine-bromine iron solution on power consumption and bromine yield has been studied. The expediency of using a closed-type electrolyzer with separation of the cathode and anode spaces using an asbestos polymer diaphragm is shown

A Grating Interferometric Acoustic Sensor Based on a Flexible Polymer Diaphragm.

This study presents a grating interferometric acoustic sensor based on a flexible polymer diaphragm. A flexible-diaphragm acoustic sensor based on grating interferometry (GI) is proposed through design, fabrication and experimental demonstration. A gold-coated polyethylene terephthalate diaphragm was used for the sensor prototype. The vibration of the diaphragm induces a change in GI cavity length, which is converted into an electrical signal by the photodetector. The experimental results show that the sensor prototype has a flat frequency response in the voice frequency band and the minimum detectable sound pressure can reach 164.8 µPa/√Hz. The sensor prototype has potential applications in speech acquisition and the measurement of water content in oil. This study provides a reference for the design of optical interferometric acoustic sensor with high performance.

A high-fidelity MEMS microphone with a polymer membrane that can detect infra-sounds

This study proposes a polymer MEMS microphone that operates through electromechanical amplitude modulation. We have developed a highly optimized MEMS structure with a flexible polymer material, resulting in a miniaturized and flexible device with excellent acoustic performance. The stiffness and damping characteristics of the polymer diaphragm are analyzed and it shows that the polymer material would be suitable for microphone applications. An equivalent circuit model is also developed for design purposes, so that the device could be properly designed using it and fabricated by in-house polymer thin film processes. The fabricated device is tested using a DC bias scheme to reach its signal-to-noise ratio (SNR) of 65 dBA within a bandwidth of 10 to 10,000 Hz, which is comparable to existing high-end commercial silicon MEMS microphones. We would then extend the frequency bands of linear detection down to the infrasound range by using electromechanical amplitude modulation. This operation scheme can also provide the microphone with no need for metal packaging. Its feasibility is confirmed theoretically by numerical simulations including electromechanical amplitude modulation and experimentally by implementing it at the PCB level. In addition, this approach enables the sensor stronger to the environmental noise so that metal shielding could be omitted.

Project-based learning through sensor characterization in a musical acoustics course.

Project-based learning engages students in practical activities related to course content and has been demonstrated to improve academic performance. Due to its reported benefits, this form of active learning was incorporated with an ongoing research project into an introductory, graduate-level Musical Acoustics course at the Peabody Institute of The Johns Hopkins University. Students applied concepts from the course to characterize a contact sensor with a polymer diaphragm for musical instrument recording. Assignments throughout the semester introduced students to completing a literature review, planning an experiment, collecting and analyzing data, and presenting results. While students were given broad goals to understand the performance of the contact sensor compared to traditional microphones, they were allowed independence in determining the specific methods used. The efficacy of the course framework and research project was assessed with student feedback provided through open-ended prompts and Likert-type survey questions. Overall, the students responded positively to the project-based learning and demonstrated mastery of the course learning objectives. The work provides a possible framework for instructors considering using project-based learning through research in their own course designs.

An Electret-Powered Skin-Attachable Auditory Sensor that Functions in Harsh Acoustic Environments.

Auditory sensors have shortcomings with respect to not only personalization with wearability and portability but also detecting a human voice clearly in a noisy environment or when a mask covers the mouth. In this work, an electret-powered and hole-patterned polymer diaphragm is exploited into a skin-attachable auditory sensor. The optimized charged electret diaphragm induces a voltage bias of >400V against the counter electrode, which reduces the necessity of a bulky power source and enables the capacitive sensor to show high sensitivity (2.2VPa-1 ) with incorporation of an elastomer nanodroplet seismic mass. The sophisticated capacitive structure with low mechanical damping enables a flat frequency response (80-3000Hz) and good linearity (50-80dBSPL ). The hole-patterned electret diaphragms help the skin-attachable sensor detect only neck-skin vibration rather than dynamic air pressure, enabling a person's voice to be detected in a harsh acoustic environment. The sensor operates reliably even in the presence of surrounding noise and when the user is wearing a gas mask. Therefore, the sensor shows strong potential of a communication tool for disaster response and quarantine activities, and of diagnosis tool for vocal healthcare applications such as cough monitoring and voice dosimetry.

Evaluation of Polymer Materials for MEMS Microphones

Polymers are attractive materials for the fabrication of micro-electro-mechanical system (MEMS) microphones because of their low Young’s moduli, generally lower processing temperatures than silicon, and simple fabrication; such microphones are sensitive and economical. However, an earlier polymer diaphragm revealed lower sensitivity than expected. In addition, the viscoelastic properties of polymer diaphragm have been considered to degrade the sensing performance due to a high-level mechanical noise. Here, we investigated the possibility of the polymer material as a MEMS microphone in terms of stiffness and damping. Stiffness was analyzed and experimentally verified. The obtained polymer diaphragm damping coefficient was compared with the coefficient of a silicon MEMS microphone to explore whether performance was degraded by material damping. All samples were fabricated using a thin film transfer method. SU-8 was mainly used but Polymethyl methacrylate (PMMA) was also selected for comparing the material damping effect. The measured residual stress of an SU-8 diaphragm was 18 MPa; the measured flexibility was similar to the state-of-art of a silicon-based MEMS microphone, and it was proven that there is room for further improvement through process optimization. The damping effect induced by viscoelasticity was very small, compared with the effect of air damping; indeed, the intrinsic damping effect of the polymer on device performance was negligible. [2021-0213]

Design and implementation of dual pressure variation chambers for bone conduction microphone

This study presents a bone conduction microphone (BCM) to detect the variation of air pressure resulted from the skull vibration. The presented BCM consists of a commercial MEMS microphone, the sensing circuits, the bulk metal, the deformable polymer diaphragm, and two printed circuit board (PCB) covers. In this design, two chambers and a vibrating spring-mass structure are hermetic sealed by two PCB covers. As the spring-mass structure vibrates, the pressure of one chamber will increase and that of another will decrease. Thus, the vibration could introduce a higher pressure load as well as a larger sensing signal for the BCM. In application, the device with the dimensions of 3.5 × 2.65 × 1.48 mm3 is implemented. Measurements show the device has a sensitivity of −38.8 dBV, THD < 0.48% at 1 kHz with 1 g excitation, and ±5 dB bandwidth for 100 Hz∼6.7 kHz. Frequency responses of different samples show good repeatability. Furthermore, air leakage effect and crosstalk of the skull vibration sensing module have also been investigated in this paper. The results demonstrate the feasibility of the presented BCM.

Three-dimensional-printed Fabry-Perot interferometer on an optical fiber tip for a gas pressure sensor.

We demonstrate a three-dimensional (3D)-printed miniature optical fiber-based polymer Fabry-Perot (FP) interferometric pressure sensor based on direct femtosecond laser writing through two-photon polymerization. An unsealed cylinder column with a suspended polymer diaphragm is directly printed on a single-mode fiber tip to form an FP cavity. Here, two FP cavities with different lengths and the same diaphragm thickness (5 µm) are presented. The fabricated FP interferometer has a fringe contrast larger than 15 dB. The experimental results show that the fabricated device with a 140 µm cavity length has a linear response to the change of pressure with a sensitivity of 3.959 nm/MPa in a range of 0-1100 kPa, and the device with a 90 µm cavity length has a linear pressure sensitivity of 4.097 nm/MPa. The temperature sensitivity is measured to be about 160.2 pm/°C and 156.8 pm/°C, respectively, within the range from 20 to 70°C. The results demonstrate that 3D-printing techniques can be used for directly fabricating FP cavities on optical fiber tips for sensing applications.

Simultaneous measurement of pressure and temperature with a single FBG embedded in a polymer diaphragm

This paper presents the development of a single polymer diaphragm-based fiber Bragg grating (FBG) sensor for simultaneous measurement of pressure and temperature. The FBG response is analyzed through a transient model for heat conduction and the pressure is estimated with the diaphragm and FBG strain, where the frequency difference between temperature and pressure variations were used to decouple both variables. Results show root mean squared error (RMSE) of 1.86 °C for the temperature analysis with constant pressure and 0.92 kPa for the pressure analysis with constant temperature. Experiments with variation of both temperature and pressure were conducted and the errors were higher than the ones with only temperature or pressure variations due to a residual cross-sensitivity. Therefore, the variation of both pressure and sensitivity leads to a RMSE of 3.88 °C and 5.13 kPa for temperature and pressure, respectively, which represent low errors of about 5% for both pressure and temperature.

Material features based compensation technique for the temperature effects in a polymer diaphragm-based FBG pressure sensor.

Fiber Bragg grating (FBG) based sensors have been applied to measure several parameters, such as pressure, vibration, liquid level, humidity, the concentration of chemical compounds, among others. An approach to measure parameters like liquid level, pressure and vibration are to embed the FBG on a diaphragm, which is generally made of a polymeric material. Nevertheless, the mechanical properties of polymers depend on temperature variation. For this reason, a polymer diaphragm can enhance the cross-sensitivity between the strain and temperature on an FBG sensor. In order to overcome this limitation, this paper presents a compensation technique for the temperature effects on an oblong polymer diaphragm-based FBG pressure sensor. The presented technique is based on the analytical model of the sensor, which takes into account the variation of the diaphragm properties with temperature obtained through a dynamic mechanical analysis of the diaphragm material. Results show that the developed technique reduces the sensor cross-sensitivity to about 1.74 Pa/°C. Furthermore, the presented technique is compared with the direct difference between the FBG strain and temperature responses presented in reference works. The comparison shows a better performance of the technique presented in this paper with respect to the cross-sensitivity and the root mean squared error.

Highly sensitive giant magnetoresistance (GMR) based ultra low differential pressure sensor

In this study, we demonstrate a simple, cost-effective, giant magnetoresistance (GMR) based magnetic pressure sensor. The basic principle lies behind the measurement of the change in the magnetic field profile generated by the deflected diaphragm attached with a permanent magnet. This magnetic field profile change on the sensor surface was measured by highly sensitive magnetoresistive gradiometer sensor. Based on studied magnetic field distribution of a magnet, a prototype pressure sensor was designed and fabricated, which consists of a polymer diaphragm, a permanent magnet and a giant magnetoresistance based magnetic field gradient sensor. The fabricated prototype was calibrated for ultra-low differential pressure range and it shows: (i) sensitivity up to 16.67 μV/V/Pa and (ii) nonlinearity of 1.5% FS in the range of 0–300 Pa. The real time application was demonstrated where, the sensor was flush mounted on a NACA 4415 airfoil, and both the static and the dynamic suction pressures were recorded as a function of the wind velocity and also with different angle of attack (AOA). The measured pressure was found to be highly accurate while compared with existing static measurement system.

Characterization of the Materials in Waste Power Banks and the Green Recovery Process

People are using power banks (PBs) to enlarge their mobile phones’ energy storage capacity in China. Large amounts of waste PBs were generated because of its short serving life. Recovery technology of waste PBs is a pressing need. However, there is little published information about the recovery technology of waste PBs. The recovery technology of spent lithium battery might be suitable for treating waste PBs. But the current method of recovering spent lithium battery is combination technologies of crushing and hydrometallurgical leaching, providing inefficient and incomplete recovery of full materials. Additionally, some wastewater was produced. In this study, the materials from waste PBs and its structures were characterized, and an environmentally friendly technology of recovering copper foil, diaphragm, cobalt, nickel, and lithium aluminum oxide from waste PBs is proposed. The technology is a combination of manual dismantling, crushing, vacuum roasting, and magnetic separation. Intact polymer diaphragm...

Investigation of intelligent reversible diaphragm using shape memory polymers

This article describes design and analysis of a novel reversible diaphragm using shape memory polymer. The reversible diaphragm could be applied to space engineering, such as propellant tank of rocket. The shape memory polymer diaphragm can automatically recover to the initial state after the overturning deformation and thus can be used repeatedly. A three-dimensional model is established to study the overturning and recovery behavior of the shape memory polymer diaphragm.The nonlinear finite element method based on the thermodynamic constitutive equations of shape memory polymer is used to obtain pressure -displacement relations and strain energy variation of SMP diaphragm with approximately hemispherical shape in the whole process of the overturning deformation. The influence of structural parameters and temperature on the overturning and recover behavior is discussed.

Noncontact Ultrasonic Detection in Low-Pressure Carbon Dioxide Medium Using High Sensitivity Fiber-Optic Fabry–Perot Sensor System

For the application of ultrasonic detection in low-pressure carbon dioxide medium, we propose a fiber-optic Fabry-Perot (F-P) ultrasonic sensor system based on an edge-stretched circular polymer diaphragm. The diaphragm is fabricated with pre-tension of 200 N/m. The demonstrated demodulation system is based on quadrature phase-shifted demodulation method. By setting the F-P cavity length and the wavelengths of distribute feedback (DFB) semiconductor lasers, two quadrature-phase interference signals can be obtained. Experimental results showed that the proposed sensor system can have a sensitivity of 10.4 nm/kPa and a signal-to-noise ratio (SNR) of 14.45 dB under gas pressure of 270 Pa in low-pressure carbon dioxide. The unique advantages of the proposed sensor system make it attractive for non-contact ultrasonic detection in low-pressure gas medium.

Polymer Microbubble-Based Fabry–Perot Fiber Interferometer and Sensing Applications

A polymer microbubble-based Fabry–Perot fiber interferometer (FPI) for pressure and temperature measurement is proposed and demonstrated. By splicing a small segment of photonic bandgap fiber to a single-mode fiber and immersing such a fiber tip into an optical adhesive, a micro air bubble could be buried into the formed polymer diaphragm. Size of air bubble and polymer diaphragm thickness can be controlled by adjusting arc discharge intensity at the fiber splice point. In order to achieve the wide dynamic range and high-resolution measurement, a demodulation algorithm based on absolute phase analysis is adopted and present high sensitivity for simultaneous pressure and temperature sensing. This simple and reproducible fabrication method of such a sensor gives an alternative way to construct FPI-based biomedical and microfluidic sensors.

Piezoresistive Polymer Diaphragm Sensor Array Using Conductive Elastomeric Nanocomposite Films for Skin-Mountable Keypad Applications

This paper reports on arrayed piezoresistive polymer diaphragm sensor made entirely of elastomer for skin-mountable keypad applications. Two-step transfer of conductive elastomeric nanocomposites (CENs) combined with soft lithographic techniques enables the achievement of elastic sensing layers with strip-patterned CENs embedded in polydimethylsiloxane (PDMS) channels. After assembling with an elastomeric bump layer, simple all-elastomer sensor architectures are successfully demonstrated. The activated buttons of the sensor can be easily and distinguishably identified by sensing the simultaneous changes in the electrical resistance of CEN strips with respect to the applied force. The straightforward sensing mechanism makes it possible to detect the exact locations of input with negligible crosstalk between adjacent sensing buttons to each other. The usability of the sensor platform as a skin-mountable keypad is also demonstrated by integrating on a wrist. [2014-0072]

Study of Three-Component FBG Vibration Sensor for Simultaneous Measurement of Vibration, Temperature, and Verticality

To achieve simultaneous measurement of measurand vibration, temperature, and verticality, a three-component fiber Brag grating (TVFBG) vibration sensor is proposed in this paper. Polymer and metal diaphragm sensitization methods are utilized to improve this sensor measurement sensitivity. Project matrix theory is adopted to analyze this sensor. Theoretically,9×9nonsingular measuring coefficient matrix of this TVFBG sensor made up by three3×3measurand coefficient matrixes is established. In order to effectively extract measurand, Hilbert-Huang transform (HHT) is accepted to process this sensor’s center wavelength signals. Calibration experiments are carried out to verify the performance of this TVFBG sensor. Experiment data confirm that this sensor has excellent frequency response and show good linearity at temperature and verticality measurement. Wrist rotation angle measurement experiment is also implemented to further identify this sensor practical value. Through analyzing by HHT, experiment results show that the angle measurement sensitivities of three fiber Brag gratings which are included in this sensor are separately 25.2 pm/°, 38.2 pm/°, and 38.3 pm/°.

Fundamental characteristics of a MEMS‐diaphragm actuator using a thermal expansion drive composed of a conductive polymer

Performance of a MEMS actuator using a thermal expansion drive of a conductive polymer (CP) is investigated by applying electricity to it. The actuator consists of a thin polymer diaphragm (5 mm diameter) and a thin CP (ion‐doped polythiophene) layer coated on the diaphragm surface. Polyimide (10 μm thickness) and PET (110 μm thickness) sheets were chosen as the diaphragm materials. The diaphragm is deflected by the thermal expansion of the CP by applying electricity to it. Merits of using the CP instead of metal are realizing flexible actuators and the applicability to a low‐heat‐resistant material diaphragm. The relationship between thickness of the CP layer (10–50 μm thickness) and electrical resistance (30–600 Ω) and the relationship between the input voltage (1–8 V) and the generated diaphragm displacement (several tens of micrometers) were investigated experimentally. These relationships were compared with those in the case of using the thermal expansion of a vapor‐deposited aluminum layer (0.1 μm thickness). The results of the investigation indicate that the diaphragm based on CP can produce the required displacement. In the case the CP‐layer‐based thermal expansion, however, larger input voltage than in the case of the aluminum‐layer‐based thermal expansion is needed to obtain the same displacement amplitudes. Therefore, the main problem concerning use of the CP‐based diaphragm is considered to be enhancing the electrical conductance of the CP layer. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Polymer Diaphragm Based Fiber Optic Fabry-Perot Acoustic Sensor

This paper presents a polymer diaphragm based Fabry-Perot (F-P) sensor system for aeroacoustic measurement in air. The diaphragm of a novel polymer material poly phthalazinone ether sulfone ketone (PPESK) is used as the sensing element. The effective dimension of the diaphragm is 1.0mm in diameter and 6μm in thickness. Thanks to the good mechanical feature of the material and the interferometric-intensity demodulation mechanism, the sensor diaphragm shift sensitivity of 0.72 nm/Pa, correspond to an acoustic pressure to voltage sensitivity of 5.56mV/Pa has been achieved. Experimental results showed that the characteristics of the sensor system is comparable with traditional electrical microphone in frequency range 100Hz to 1kHz and the sensor has the potential to be used as an optical microphone.

Miniature fiber-tip photoacoustic spectrometer for trace gas detection

We demonstrate a fiber-tip photoacoustic spectrometric sensor for trace gas detection. The sensor head is a miniature fiber-tip hollow-cavity with a deflectable polymer diaphragm. Periodic light absorption of gas molecules within the cavity generates an acoustic pressure wave, which causes deflection of the diaphragm. The hollow cavity also is a Fabry-Perot interferometer with which the diaphragm deflection is detected with high sensitivity. Experimental test around the P(9) absorption line of C(2)H(2) achieved a minimum detectable gas concentration of 4.3 ppm with an excitation laser power of 8 mW. The miniature sensor head and fiber optic detection system make this type of spectrometers ideally suited for remote and space-limited applications as well as for multipoint detection in a multiplexed fiber optic sensor network.