Screen‐Printed Soft Capacitive Sensors for Spatial Mapping of Both Positive and Negative Pressures

Abstract

Soft pressure sensors are one class of the essential devices for robotics and wearable device applications. Despite the tremendous progress, sensors that can reliably detect both positive and negative pressures have not yet been demonstrated. In this paper, a soft capacitive pressure sensor, made using a convenient and low-cost screen-printing process that can reliably detect both positive and negative pressures from −60 to 20 kPa, is reported. The sensor is made with an Ecoflex-0030 dielectric layer, conductive and stretchable poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (with ionic additives) electrodes, and polydimethylsiloxane encapsulation layers. Air gaps are designed and incorporated into the dielectric layer to significantly enhance the sample deformation and pressure response especially to negative pressure. The sensor exhibits repeatable response for thousands of cycles, even under bending or stretching conditions. Lastly, to demonstrate the practical application, a 12 × 12-pixel sensor array that can automatically measure both positive and negative pressure distributions has been reported under −20 and 10 kPa.

Inkjet‐Printed Soft Resistive Pressure Sensor Patch for Wearable Electronics Applications

“…The experimental results again indicate that better sensitivity can be achieved by using thinner and softer PDMS substrate, which is in good agreement with the simulation results above in Figure c. Furthermore, the sensitivity of 0.48 kPa −1 is higher than widely reported capacitive pressure sensors, whose sensitivity typically range from as low as ≈0.002 to 0.15 kPa −1 with texturized dielectric layer prepared using sophisticated microfabrication process . The sensitivity is also comparable with many previously reported resistive pressure sensors based on various types of sensing materials (Table S1, Supporting Information).…”

High-k, Ultrastretchable Self-Enclosed Ionic Liquid-Elastomer Composites for Soft Robotics and Flexible Electronics

“…Typically, the sensitivity of capacitive pressure sensors is increased by microstructuring, which increases fabrication complexity and opaqueness . The sensitivity obtained with these thick PDMS + EMIMTFSI (20%) films compares favorably to recent reports, even without microstructuration. − Figure f shows the variation of measured capacitance with time and applied pressure. Capacitance remains stable over time and follows the pressure curve, and immediately returns to the original state after pressure removal (Figure f and Movie S2) with no hysteresis.…”

Highly Sensitive Capacitive Pressure Sensors over a Wide Pressure Range Enabled by the Hybrid Responses of a Highly Porous Nanocomposite

“…[ 60,67,68,71,78 ] The sensitivity of the HRPS changes with applied pressure and is found to be 3.13 kPa −1 within 0–1 kPa, 1.65 kPa −1 within 1–5 kPa, 1.16 kPa −1 within 5–10 kPa, 0.68 kPa −1 within 10–30 kPa, and 0.43 kPa −1 within 30–50 kPa when doped with 0.5 wt% CNT. The sensitivity of the HRPS exceeds that of other capacitive pressure sensors reported in the recent decade in the pressure range above 3 kPa (Figure 2e) [ 7,9,13,29–33,50–53,55,56,61,64–70 ] . Notably, this improvement is most impressive in the large pressure regime, with a maximum of 423% within 10–30 kPa.…”