Use of Surface Penetration Technology to Fabricate Superhydrophobic Multifunctional Strain Sensors with an Ultrawide Sensing Range

Abstract

Flexible sensors with wide sensing ranges require responsiveness under tiny and large strains. However, the development of strain sensors with wide detection ranges is still a great challenge due to the conflict between the tiny strain requirements of sparse conductive networks and the large strain requirement of dense conductive networks. Herein, we present a facile method for fabricating a gradient conductive network composed of sparse and dense conductive networks. The surface penetration technology in which carbon black (CB) penetrated from the natural rubber latex (NRL) glove surface to the interior was used to fabricate a gradient conductive network. The prolonged immersion time from 1 to 30 min caused the penetration depth of CB to increase from 2 to 80 μm. Moreover, CB formed hierarchical rough micro- and nanoscale structures, creating a superhydrophobic surface. The gradient conductive network of sensors produced an ultrawide detection range of strain (0.05–300%) and excellent reliability and reproducibility. The sensors can detect a wide range of human motions, from tiny (wrist pulse) to large (joint movements) motion monitoring. The flexible sensors attached to a flexible basement can be used to detect pressure in a wide detection range (1.7–2900 kPa). Pressure responsiveness was used to detect the weight, sound pressure, and dripping of tiny droplets. The sensor showed an excellent response to organic solvents, and the response intensity increased with the increasing swelling degree of the solvent for NRL.

Recent Progress in Conducting Polymer Composite/Nanofiber-Based Strain and Pressure Sensors

“…Typical gradient conductive networks afford a wide detection range of about 300%, with a better reproducible sensory response. Gradient structures allowed for better harvesting of hysteresis characteristics on straining by up to 100% strain [188].…”

Fabrication of conductive and superhydrophobic poly(lactic acid) nonwoven fabric for human motion detection

“…Superhydrophobic surfaces with water contact angle (WCA) above 150 have attracted enormous attention due to their great application potential in oil-water separation, self-cleaning, antiicing, and microfluidics. [23][24][25][26][27] In recent years, superhydrophobic surface has been incorporated into piezoresistive pressure sensor to improve the water repellency by some researchers, while the substrates are difficult to be degraded, including polyimide, 28 polyester, 29 rubber, 30,31 and so forth. Therefore, the design and preparation of piezoresistive pressure sensors integrating with biodegradability and superhydrophobicity is an important development direction, which cannot only widen application range, but also benefit for environment protection.…”

“…However, due to the lack of hydrophobicity, these sensors are easily affected by water to cause a short circuit, which limited their practical application under watery environment. Superhydrophobic surfaces with water contact angle (WCA) above 150° have attracted enormous attention due to their great application potential in oil–water separation, self‐cleaning, antiicing, and microfluidics 23‐27 . In recent years, superhydrophobic surface has been incorporated into piezoresistive pressure sensor to improve the water repellency by some researchers, while the substrates are difficult to be degraded, including polyimide, 28 polyester, 29 rubber, 30,31 and so forth.…”

3D Printing of a Flexible Inclined‐Tip Cone Array‐Based Pressure Sensor

“…Flexible pressure sensors are widely used in e‐skins, [ 1–3 ] sports‐health monitoring, [ 4–9 ] and pulse‐wave testing. [ 10–15 ] Pressure sensors with high sensitivity and a wide range of detection are particularly important for the detection of physiological signals.…”

“…Flexible pressure sensors are widely used in e-skins, [1][2][3] sportshealth monitoring, [4][5][6][7][8][9] and pulse-wave testing. [10][11][12][13][14][15] Pressure sensors with high sensitivity and a wide range of detection are high-pressure range conditions, the array compresses layer by layer, responding to the pressure changes through squeezing deformation, thereby effectively improving the pressure detection range.…”