Ultrasensitive and Highly Compressible Piezoresistive Sensor Based on Polyurethane Sponge Coated with a Cracked Cellulose Nanofibril/Silver Nanowire Layer

Abstract

With the rapid development of flexible wearable electronics, a piezoresistive sensor with low detection limit and wide strain sensing range turns out to be a great challenge for its application in this field. Here, a cracked cellulose nanofibril/ silver nanowire (CA) layer-coated polyurethane (PU) sponge was acquired through a simple dip-coating process followed by precompression treatment. The electrical conductivity and mechanical property of the conductive CA@PU sponge could be effectively tuned through changing the dip-coating number. As a piezoresistive sensor, the sponge exhibited the capability of detecting both small and large motions over a wide compression strain range of 0−80%. Based on the "crack effect", the sensor possessed a detection limit as low as 0.2% and the gauge factor [GF, GF = (ΔR/R 0 )/ε, where ΔR, R 0 , and ε represent the instantaneous resistance change, original resistance, and strain applied, respectively] was as high as 26.07 in the strain range of 0−0.6%. Moreover, the "contact effect" enabled the sensor to be applicable for larger strain, and the GF decreased first and then became stable with increasing compression strain. In addition, frequency-and strain-dependent sensing performances were observed, demonstrating that the sensor can respond reliably to different applied frequencies and strains. Furthermore, the sensor displayed exceptional stability, repeatability, and durability over 500 cycles. Finally, the sensor could be applicable for the detection of various human bodily motions, such as phonation, stamping, knee bending, and wrist bending. Most importantly, the sponge also exhibited great potential for the fabrication of artificial electronic skin. Herein, the conductive CA@PU sponge will undoubtedly promote the development of high-performance flexible wearable electronics.

Effects of flame‐retardant ramie fiber on enhancing performance of the rigid polyurethane foams

“…Polyurethane is one of the most versatile materials which have been widely used in furniture, roofs, medical equipment, automotive interior materials, etc . Rigid polyurethane foams (RPUF), for one, is extensively applied as external wall insulation, foundation reinforcement of building, and decoration due to its excellent properties such as excellent mechanical properties, low thermal conductivity, rapid expansion and solidification, excellent corrosion, and water resistance …”

Facile Preparation of Highly Stretchable TPU/Ag Nanowire Strain Sensor with Spring-Like Configuration

“…Flexible wearable devices have gained considerable attention and experienced rapid growth in recent years [1][2][3][4][5][6][7][8]. Many efforts have been dedicated to integrate the attributes of low cost, lightweight, stability, small size, flexibility, and multi-functional sensitivity to the flexible sensor, which is an important branch of wearable devices [4][5][6][7][8][9].…”

“…The other is carrying out novel configuration designs, including percolation network, island bridge, serpentine configuration, sponge structure, chess-like configuration, twisted configuration, and buckled configuration [11,[15][16][17][18][19][20][21][22][23][24]. For example, cracked cellulose nanofibril/silver nanowire layer-coated polyurethane (PU) sponge was acquired through a simple dip-coating process, and the obtained strain sensor exhibited a high sensitivity over a detection range of 50% compression strain due to the high porosity and good elasticity of the polymer matrix [2]. Compared to other configurations, the wavy, buckled, and wrinkled configurations are relatively simple to attain [9], and the chess-like configuration is relatively popular.…”

Effect of Organo‐Modified Montmorillonite on the Morphology and Properties of SEBS/TPU Nanocomposites

“…The alternating diisocyanate and so‐called chain “extender” molecules form (i.e., diol or diamine) a glassy or semicrystalline hard segment, while the linear long‐chain diol makes up a rubbery soft segment . TPU stands as a versatile group of polymers . They exhibit a wide range of physical properties, such as good mechanical and elastic properties, hardness, and thermal stability .…”