Stretchable Array of Highly Sensitive Pressure Sensors Consisting of Polyaniline Nanofibers and Au-Coated Polydimethylsiloxane Micropillars

Abstract

We report on the facile fabrication of a stretchable array of highly sensitive pressure sensors. The proposed pressure sensor consists of the top layer of Au-deposited polydimethylsiloxane (PDMS) micropillars and the bottom layer of conductive polyaniline nanofibers on a polyethylene terephthalate substrate. The sensors are operated by the changes in contact resistance between Au-coated micropillars and polyaniline according to the varying pressure. The fabricated pressure sensor exhibits a sensitivity of 2.0 kPa(-1) in the pressure range below 0.22 kPa, a low detection limit of 15 Pa, a fast response time of 50 ms, and high stability over 10000 cycles of pressure loading/unloading with a low operating voltage of 1.0 V. The sensor is also capable of noninvasively detecting human-pulse waveforms from carotid and radial artery. A 5 × 5 array of the pressure sensors on the deformable substrate, which consists of PDMS islands for sensors and the mixed thin film of PDMS and Ecoflex with embedded liquid metal interconnections, shows stable sensing of pressure under biaxial stretching by 15%. The strain distribution obtained by the finite element method confirms that the maximum strain applied to the pressure sensor in the strain-suppressed region is less than 0.04% under a 15% biaxial strain of the unit module. This work demonstrates the potential application of our proposed stretchable pressure sensor array for wearable and artificial electronic skin devices.

Tailoring force sensitivity and selectivity by microstructure engineering of multidirectional electronic skins

“…Single-sided microstructured films have been widely employed to enhance the performance of flexible pressure sensors 10,14,17,32 and triboelectric generators 11,22 . For pressure-sensitive piezoresistance, a flat indium tin oxide (ITO) film was used as the top electrode on the surface of micropatterned composite films (Fig.…”

“…On the other hand, a large variation in local strain and compressibility of pyramid-shaped microstructures enhance force sensitivity and expand the dynamic sensing range of e-skins [13][14][15] . Inspired by the hierarchical structures in nature, such as insect legs, gecko foots, and beetle wings, pillar-shaped microstructures have been reported to provide selective and directional force-sensing properties, as well as stress-confinement effects [16][17][18][19] . In addition, the strong adhesion properties of pillar structures provide a new possibility for skinattachable and wearable healthcare devices 1 .…”

“…In addition, the strong adhesion properties of pillar structures provide a new possibility for skinattachable and wearable healthcare devices 1 . Considering these geometrical effects of microstructure arrays on the performance of e-skins, previously, geometrical parameters such as shape, size, and space of microstructure arrays have been controlled to enhance the mechanical sensitivity and operation range of piezoresistive 20 and capacitive e-skins 15 and the power generation of self-powered e-skins [16][17][18][21][22][23] . Since the geometrical shape of microstructure significantly affects the contact area and localized stress of microstructure under pressure, several attempts to find the relationship between the shape of microstructure and the sensitivity of various eskins have been performed.…”

Nanomaterial‐Enabled Wearable Sensors for Healthcare

“…[6,138] Numerous materials and configurations have been reported for resistive pressure sensing. Pressure sensitive pathways can be formed using interlocked structures, [139][140][141][142][143][144] percolative networks of nanomaterials, [57,145,146] microfabricated structures (e.g., micropyramids, micropillars), [147][148][149] porous structures (e.g., sponges, foams, porous rubbers) [26,150,151] and so forth. For example, Figure 5a presents the working principle of a pressure sensor using interlocked microdome array.…”

Polyurethane foam coated with a multi-walled carbon nanotube/polyaniline nanocomposite for a skin-like stretchable array of multi-functional sensors

“…11 Polyaniline (PANI) is considered one of the most promising and widely applied sensing materials because of its low production cost, environmental stability and acceptable conductance as well as its unique ammonia (NH 3 ) gas-sensing ability. 15 In addition, PANI has thermoelectric properties that allow it to exhibit output voltage according to a change in temperature. Furthermore, MWCNT-PANI nanocomposites have shown superior performance in terms of the Seebeck coefficient, electrical conductivity and thermal conductivity compared with their individual components.…”