Anodized Aluminum Oxide-Assisted Low-Cost Flexible Capacitive Pressure Sensors Based on Double-Sided Nanopillars by a Facile Fabrication Method

Abstract

Flexible pressure sensors have garnered enormous attention in recent years as they hold great promise in wearable electronic devices. However, the realization of a high-performance flexible pressure sensor via a facile and costeffective approach still remains a challenge. In this work, a capacitive pressure sensor based on a poly(vinylidenefluorideco-trifluoroethylene) [P(VDF-TrFE)] dielectric film that incorporates nanopillars into both sides is demonstrated. Unlike the previous complicated and expensive methods, large-scale regular and uniform nanopillars are easily and economically achieved by the pattern transfer of anodized aluminum oxide templates. The double-sided nanopillars constituting the P(VDF-TrFE) dielectric layer enable the pressure sensor with high sensitivity (∼0.35 kPa −1 ), wide working range (4 Pa to 25 kPa), short response time (∼48 ms), and excellent durability. In addition to these salient features, our sensor also exhibits superior performances under bending states, ensuring that it can be used for detecting diverse practical stimuli as experimentally validated by perceiving real-time and in-site human physiological signals and body motions that, respectively, correspond to the low-and high-pressure range. A sensor array is finally constructed and is shown to be capable of perceiving the spatial pressure distribution of either a contact or noncontact object. These demonstrations show a promising future of our sensor in healthcare monitoring, smart robot skin, and human− machine interfaces.

Flexible and Stretchable Capacitive Sensors with Different Microstructures

“…When materials with a lowtemperature coefficient are selected as the electrodes of the capacitive sensors, their temperature coefficients are extremely small and are almost unaffected by temperature. [32] In addition, capacitive sensors have the advantages of simple device structure, low power consumption, low detection limit, wide application range, fast dynamic response, and endurability, [35][36][37][38][39][40][41] which have been extensively studied and applied in E-skin, [42,43] medical prosthetics, [44] wearable devices, [13,45] biometrics, [38,46] touchpads and touch screens, [47][48][49] and other consumer electronics fields. [47,[50][51][52][53] In the past few decades, various methods for fabricating flexible capacitive sensors have been proposed.…”

“…[74] However, the unchanged volume of the polymer dielectric layer limits the improvement in sensitivity. [37,39] Most polymer elastomers have severe viscoelasticity and interfacial adhesion, [55,81] which increase the hysteresis and reduce the response speed of the device. [51,82] In practical applications, especially in biomedicine, the response time affects the speed of signal collection and processing.…”

A Facile Strategy for Low Young's Modulus PDMS Microbeads Enhanced Flexible Capacitive Pressure Sensors

“…where ε air , ε PDMS , and ε Ecoflex are the relative permittivity of air, PDMS, and Ecoflex, respectively; V air and V PDMS are the volume proportion of the air and PDMS microbeads, respectively. [6,26] Here, ε air = 1, ε PDMS ≈ 2.4, and ε Ecoflex ≈ 2.17. [27] Therefore, when the dielectric layer is compressed, V air will decrease while V PDMS will increase, resulting in an increase in ε r , making ε r ' > ε r , which will further enhance the capacitive response of the sensor.…”

“…Flexible pressure sensors are attractive for various fields, such as human-machine interaction, wearable electronic devices, and health monitoring. [1][2][3][4][5][6][7] There are four major types of flexible pressure sensors, i.e., piezoresistive type, [2] capacitive type, [3,4,8] piezoelectric type, [5] and triboelectric type. [9] Among them, the capacitive pressure sensor has been widely investigated for its advantages, such as straightforward structure, low power consumption, excellent stability, and rapid response.…”

A Wearable Sensor Based on Gold Nanowires/Textile and Its Integrated Smart Glove for Motion Monitoring and Gesture Expression

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According to the sensing mechanism, pressure sensors can be divided into five types: piezoelectric, [1,2] piezoelectric resistivity, [3][4][5][6] capacitance, [7,8] triboelectric, [9,10] and transistor. [11] Piezoresistive sensors have attracted much attention in recent years due to their simple design, low manufacturing cost, good signal repeatability, low power consumption, low working voltage, and simple measurement scheme.

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