Coaxial Printing of Silicone Elastomer Composite Fibers for Stretchable and Wearable Piezoresistive Sensors

Abstract

Despite the tremendous efforts dedicated to developing various wearable piezoresistive sensors with sufficient stretchability and high sensitivity, challenges remain pertaining to fabrication scalability, cost, and efficiency. In this study, a facile, scalable, and low-cost coaxial printing strategy is employed to fabricate stretchable and flexible fibers with a core–sheath structure for wearable strain sensors. The highly viscous silica-modified silicone elastomer solution is used to print the insulating sheath layer, and the silicone elastomer solutions containing multi-walled carbon nanotubes (CNTs) are used as the core inks to print the conductive inner layer. With the addition of silica powders as viscosifiers, silica-filled silicone ink (sheath ink) converts to printable ink. The dimensions of the printed coaxial fibers can be flexibly controlled via adjusting the extrusion pressure of the inks. In addition, the electro-mechanical responses of the fiber-shaped strain sensors are investigated. The printed stretchable and wearable fiber-like CNT-based strain sensor exhibits outstanding sensitivities with gauge factors (GFs) of 1.4 to 2.5 × 106, a large stretchability of 150%, and excellent waterproof performance. Furthermore, the sensor can detect a strain of 0.1% and showed stable responses for over 15,000 cycles (high durability). The printed fiber-shaped sensor demonstrated capabilities of detecting and differentiating human joint movements and monitoring balloon inflation. These results obtained demonstrate that the one-step printed fiber-like strain sensors have potential applications in wearable devices, soft robotics, and electronic skins.

Calculation of the Electrical Conductivity of Polymer Nanocomposites Assuming the Interphase Layer Surrounding Carbon Nanotubes

“…Comparison between experimental and theoretical data (Equation (12)) for (a) epoxy/MWCNT [55] and (b) UPE/MWCNT [58] samples. Figure 2 illustrates "ϕ e f f " levels at different values of "R", "l", "t" and "u" parameters using Equation (4). According to Figure 2a, "ϕ e f f " only depends on "R" parameter and "l" cannot affect it.…”

Highly Stretchable, Strain-Sensitive, and Ionic-Conductive Cellulose-Based Hydrogels for Wearable Sensors

“…Herein, we reported highly stretchable, strain-sensitive, and ionic-conductive CHs prepared by the random copolymerization of allyl cellulose and acrylic acid in NaOH/urea aqueous solution. The acquired hydrogels exhibited high stretchability (with strain up to ~142%) and good transparency As shown in Figure 5A, the resistance change ratio variation (∆R/R 0 ) of CH3 displayed a highly linear relationship (R 0-100% 2 = 0.980), and the gauge factor (GF, representative of sensitivity) [3,39] was 0.26, which implied that CH3 could serve as a wide-range and highly reliable tensile sensor. More importantly, this sensor could also reliably detect a tiny strain of 10%, because its highly linear relationship between resistance change ratio variation and strain (R 0-10% 2 = 0.999) and good GF (0.1), as shown in Figure 5B.…”

Study on the Effects of the Interphase Region on the Network Properties in Polymer Carbon Nanotube Nanocomposites

“…Many researchers have focused on polymer/carbon nanotubes (CNT) nanocomposites because their very low volume fractions show effective mechanical, thermal and chemical properties by preserving low density, transparency and simple processing [1][2][3][4][5][6][7][8][9][10]. The addition of CNT or graphene to polymers forms conductive nanocomposites, which has produced scientific interest in the research communities due to their potential applications in different fields, such as electronics and sensors [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25].…”