Abstract
In this work, deionized (DI) water dissociation was used to treat and change the contact angle of the surface of stainless steel substrates followed by the spin coating of P(VDF-TrFE) material for the fabrication of tactile sensors. The contact angle of the stainless steel surface decreased 14° at −30 V treatment; thus, the adhesion strength between the P(VDF-TrFE) thin film and the stainless steel substrate increased by 90%. Although the adhesion strength was increased at negative voltage treatment, it is observed that the crystallinity value of the P(VDF-TrFE) thin film declined to 37% at −60 V. In addition, the remanent polarization value of the P(VDF-TrFE) thin film declined from 5.6 μC/cm2 to 4.61 μC/cm2 for treatment voltages between −5 V and −60 V. A maximum value of approximately 1000 KV/cm of the coercive field value was obtained with the treatment at −15 V. The d33 value was approximately −10.7 pC/N for the substrate treated at 0 V and reached a minimum of −5 pC/N for treatment at −60 V. By using the P(VDF-TrFE) thin-film as the sensing material for tactile sensors, human pulse measurements were obtained from areas including the carotid, brachial, ankle, radial artery, and apical regions. In addition, the tactile sensor is suitable for monitoring the Cun, Guan, and Chi acupoints located at the radial artery region in Traditional Chinese Medicine (TCM). Waveform measurements of the Cun, Guan, and Chi acupoints are crucial because, in TCM, the various waveforms provided information regarding the health conditions of organs.
Highlights
Numerous research institutes have explored applications of ferroelectric materials, including lead zirconium titanate (PZT) [1,2], polyvinylidene difluoride (PVDF) [3,4,5], and polyvinylidene-trifluoroethylene (PVDF-TrFE) [6,7,8]
This study shows that the proposed P(VDF-TrFE)-based flexible tactile sensors can effectively detect various amplitudes and waveforms at different areas of the human body
This study demonstrates the successful fabrication and functionality of P(VDF-TrFE) flexible tactile sensors
Summary
Numerous research institutes have explored applications of ferroelectric materials, including lead zirconium titanate (PZT) [1,2], polyvinylidene difluoride (PVDF) [3,4,5], and polyvinylidene-trifluoroethylene (PVDF-TrFE) [6,7,8]. PVDF and P(VDF-TrFE) are polymer ferroelectric materials that offer the advantages of mechanical flexibility, biocompatibility, low crystallization temperatures, and a high piezoelectric constant These materials are widely employed in sensing applications such as pressure sensors, tactile sensors, pyroelectric detectors, and thin-film transistors. Regarding piezoelectric-based tactile sensors, mechanical energy can be transformed into electrical energy by applying pressure These sensors have the advantage of high sensitivity, improved hysteresis, excellent repeatability, and high durability and, are employed for human health biomedical monitoring. Other sensors, such as piezoelectric-based sensors [18], optical sensors [19], laser Doppler sensors [20], and CMOS image sensors [21], have been used to measure the physiological signals of the human body, such as the heartbeat, breathing, and pulse waveform at artery regions. It is believed that these tactile sensors can be widely used for micro-electromechanical systems (MEMS) applications, such as energy harvesting [27], large area tactile sensors array [28], robot hands [29], pressure sensors [30], and fingerprint applications [31]
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