Silver Nanowire–Bacterial Cellulose Composite Fiber-Based Sensor for Highly Sensitive Detection of Pressure and Proximity

Abstract

Fiber-based sensors are desirable to provide an immersive experience for users in the human−computer interface. We report a hierarchically porous silver nanowire-bacterial cellulose fiber that can be utilized for sensitive detection of both pressure and proximity of human fingers. The conductive fiber was synthesized via continuous wetspinning at a speed of 20 m/min, with a diameter of 53 μm, the electrical conductivity of 1.3 × 10 4 S/cm, a tensile strength of 198 MPa, and elongation strain of 3.0% at break. The fibers were coaxially coated with a 10 μm thick poly(dimethylsiloxane) dielectric elastomer to form the fiber sensor element which is thinner than a human hair. Two of the sensor fibers were laid diagonally, and the capacitance changes between the conductive cores were measured in response to pressure and proximity. In the touch mode, a fiber-based sensor experienced monotonic capacitance increase in the pressure range from 0 to 460 kPa, and a linear response with a high sensitivity of 5.49 kPa −1 was obtained in the low-pressure regime (<0.5 kPa). In touchless mode, the sensor is highly sensitive to objects at a distance of up to 30 cm. Also, the fiber can be easily stitched into garments as comfortable and fashionable sensors to detect heartbeat and vocal pulses. A fiber sensor array is able to serve as a touchless piano to play music and accurately determine the proximity of an object. A 2 × 2 array was further shown for two-and threedimensional location detection of remote objects.

Cutaneous Ionogel Mechanoreceptors for Soft Machines, Physiological Sensing, and Amputee Prostheses

“…We compare our touch skin with previously reported soft pressure sensors based on hydrogels [ 15,17,21,30 ] and other conductive soft materials. [ 3,16,26–29,31,43–46 ] The results demonstrate that our touch skin enables robust robotic applications and achieves superior sensing performances—including high sensitivity and resolution, fast response speed, and a broad detection range (see Table 1). The robotic skin can provide an industrial robot and a transradial amputee with real‐time sensory feedback, which facilitates dexterous manipulation and secure interaction with the external environment.…”

Textile-Based Mechanical Sensors: A Review

“…Capacitive TMSs can be obtained by fiber crossing. Guan et al [48] prepared silver nanowire-bacterial cellulose fibers with porous structures using a wetspinning process and then coaxially coated the fibers with PDMS to produce functional fibers with a core-sheath structure (Figure 2b). A capacitive multifunctional sensor was fabricated by arranging the functional fibers crosswise to form an interpenetrating network, in which the AgNWs-bacterial cellulose fibers served as electrodes and the PDMS coating acted as the dielectric layer.…”

“…In addition, such TMSs often present the advantages of fast response time and high sensitivity [56], giving them great prospects in wearable devices. Tan et al [50] prepared piezoelectric TMSs using the piezoelectric effect of the single-crystalline ZnO nanorods grown on conductive [47]; (b) crossed fiber capacitive sensors, reproduced with permission from [48]; (c) helix fiber capacitive sensors, reproduced with permission from [49]; (d) sandwich structure piezoelectric sensors, reproduced with permission from [50]; (e) double-layer piezoelectric sensors with vertical arrangement, reproduced with permission from [51]; (f) coaxial fiber triboelectric sensors, reproduced with permission from [52]; and (g) double-layer triboelectric sensors, reproduced with permission from ref. [53].…”

“…PDMS means polydimethylsiloxane, PI means polyimide, rGO means reduced graphene oxide and PVDF means polyvinylidene fluoride. (a) sandwich structure fabric capacitive sensors, reproduced with permission from[47]; (b) crossed fiber capacitive sensors, reproduced with permission from[48]; (c) helix fiber capacitive sensors, reproduced with permission from[49]; (d) sandwich structure piezoelectric sensors, reproduced with permission from[50]; (e) double-layer piezoelectric sensors with vertical arrangement, reproduced with permission from[51]; (f) coaxial fiber triboelectric sensors, reproduced with permission from[52]; and (g) double-layer triboelectric sensors, reproduced with permission from ref [53]…”

Textile Triboelectric Nanogenerators for Wearable Pulse Wave Monitoring

“…Thus, these parameters can provide clinically valuable information for diagnosing a variety of CVDs, for example arrhythmia, atrial septal defect, atherosclerosis, arterial hypertension (HTN), and coronary heart disease (CHD) [6]. To continuously measure the human pulse wave in a cuffless manner, a variety of wearable pulse sensors have been developed, including piezoelectric [7][8][9], resistive [10][11][12][13][14][15][16][17], capacitive [18][19][20][21][22], transistor-based pressure sensors [23][24][25], ultrasonic sensors [26], and photoplethysmogram sensors [27]. These sensors have received extensive attention because they can continuously monitor the human pulse wave in a noninvasive wearable manner.…”