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

TLDR

Fiber‑based sensors are sought after for immersive human–computer interfaces. The study presents a hierarchically porous silver nanowire–bacterial cellulose fiber for sensitive pressure and proximity detection of human fingers. The fiber was fabricated by continuous wet‑spinning into a 53 µm diameter strand with 1.3 × 10⁴ S cm⁻¹ conductivity, 198 MPa tensile strength, and 3 % elongation, then coated with a 10 µm PDMS dielectric to form a sub‑hair‑thick sensor element whose diagonal arrangement allows capacitance changes to be measured under pressure and proximity. The sensor shows a monotonic capacitance rise from 0 to 460 kPa with a linear, highly sensitive response (5.49 kPa⁻¹) below 0.5 kPa, detects objects up to 30 cm in touchless mode, can be integrated into garments for heartbeat and vocal pulse sensing, and a 2 × 2 array enables touchless piano play and precise 2‑ and 3‑D remote object localization.

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 wet-spinning at a speed of 20 m/min, with a diameter of 53 μm, the electrical conductivity of 1.3 × 104 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 three-dimensional location detection of remote objects.