Silver nanowire-embedded PDMS with a multiscale structure for a highly sensitive and robust flexible pressure sensor

Abstract

The development of highly sensitive pressure sensors with a low-cost and facile fabrication technique is desirable for electronic skins and wearable sensing devices. Here a low-cost and facile fabrication strategy to obtain multiscale-structured elastomeric electrodes and a highly sensitive and robust flexible pressure sensor is presented. The principles of spontaneous buckle formation of the PDMS surface and the embedding of silver nanowires are used to fabricate the multiscale-structured elastomeric electrode. By laminating the multiscale-structured elastomeric electrode onto the dielectric layer/bottom electrode template, the pressure sensor can be obtained. The pressure sensor is based on the capacitive sensing mechanism and shows high sensitivity (>3.8 kPa(-1)), fast response and relaxation time (<150 ms), high bending stability and high cycle stability. The fabrication process can be easily scaled up to produce pressure sensor arrays and they can detect the spatial distribution of the applied pressure. It is also demonstrated that the fingertip pressure sensing device can sense the pressure distribution of each finger, when grabbing an object.

Nanomaterial‐Enabled Wearable Sensors for Healthcare

“…Figure 5e shows a capacitive pressure sensor based on multiscale-structured AgNW/PDMS electrodes fabricated by prestretching and hardening the top surface using UV treatment. [158] The pressure sensor displayed high sensitivity of 3.8 kPa −1 for 45-500 Pa, 0.8 kPa −1 for 500 Pa to 2.5 kPa and 0.35 kPa −1 for 2.5-4.5 kPa. Another strategy to increase the effective dielectric constant is to add conductive fillers into the dielectric just below the percolation threshold.…”

“…[152][153][154] Highly deformable dielectric materials can be realized by using commercial porous tapes, [43] creating microstructures in elastomers using a mold (e.g., the surface of matte glass, [155] a micromachined Si mold, [131] or the surface of lotus leaf [156] ), creating porous elastomers using sugar cubes as the template, [157] or fabricating buckled structures through prestretching and releasing. [158] When the air gap is compressed, the effective dielectric constant is increased under pressure, as the dielectric constant of air is smaller than that of the dielectric material used for the sensor. Figure 5d highlights a capacitive pressure sensor with CNT/PDMS as the two electrodes, an air gap and porous PDMS with hollow micropillars as the dielectric.…”

“…Reproduced with permission. [158] Copyright 2015, Royal Society of Chemistry. Besides the widely used resistive and capacitive mechanisms, progress has been made to develop wearable piezoelectric [22,58,59,159] and triboelectric [160][161][162] pressure sensors.…”

“…[46] Pressure sensors can also be attached onto the hand to monitor the pressure distribution during grabbing an object. [158] Heart rate, respiration rate, body motions, and other para meters collected from wearable sensors can provide crucial information to evaluate and improve the performances during rehabilitation or sports. Simultaneous and continuous monitoring of sweat profile during exercise can be conducted using wearable electrochemical sensors.…”

“…Successful mimicking of human skin requires good mechanical compliance, high sensitivity, good spatiotemporal resolution, and multimodal sensing capability. [20] A multitude of pressure sensing arrays have been demonstrated to capture the spatial pressure distributions induced by different sources, such as a static object placed onto the sensing array, [57,139,141,158,203] gas flow, [141,144,153] bouncing of a water droplet (Figure 11a), [139] finger touch, [144,161] and acoustic vibration. [144,203] Besides the pressure sensors, strain sensors were used to detect the movement of a cricket and sound signals.…”