Porous Polydimethylsiloxane Elastomer Hybrid with Zinc Oxide Nanowire for Wearable, Wide-Range, and Low Detection Limit Capacitive Pressure Sensor

Abstract

We propose a flexible capacitive pressure sensor that utilizes porous polydimethylsiloxane elastomer with zinc oxide nanowire as nanocomposite dielectric layer via a simple porogen-assisted process. With the incorporation of nanowires into the porous elastomer, our capacitive pressure sensor is not only highly responsive to subtle stimuli but vigorously so to gentle touch and verbal stimulation from 0 to 50 kPa. The fabricated zinc oxide nanowire–porous polydimethylsiloxane sensor exhibits superior sensitivity of 0.717 kPa−1, 0.360 kPa−1, and 0.200 kPa−1 at the pressure regimes of 0–50 Pa, 50–1000 Pa, and 1000–3000 Pa, respectively, presenting an approximate enhancement by 21−100 times when compared to that of a flat polydimethylsiloxane device. The nanocomposite dielectric layer also reveals an ultralow detection limit of 1.0 Pa, good stability, and durability after 4000 loading–unloading cycles, making it capable of perception of various human motions, such as finger bending, calligraphy writing, throat vibration, and airflow blowing. A proof-of-concept trial in hydrostatic water pressure sensing has been demonstrated with the proposed sensors, which can detect tiny changes in water pressure and may be helpful for underwater sensing research. This work brings out the efficacy of constructing wearable capacitive pressure sensors based on a porous dielectric hybrid with stress-sensitive nanostructures, providing wide prospective applications in wearable electronics, health monitoring, and smart artificial robotics/prosthetics.

Bioinspired Hierarchical Structure for an Ultrawide‐Range Multifunctional Flexible Sensor Using Porous Expandable Polyethylene/Loofah‐Like Polyurethane Sponge Material

“…As summarized in Figure 3e, we compared our double‐layered sensor with other sensors from recent studies using the microstructure. [ 53–63 ] The comparison result showed that this double‐layer structure sensor had the distinctively lowest sensitivity loss (about 0.0195% kPa −1 ) with the widest pressure detection range (see details in Table S1, Supporting Information), outperforming other capacitive pressure sensors reported in the literature to the best of our knowledge.…”

Porous Elastomer Based Wide Range Flexible Pressure Sensor for Autonomous Underwater Vehicles

“…However, they have been mainly been used for applications such as imaging [31] and wearables [29,30] in the underwater environment, and not necessarily to measure the water pressure itself. For this reason, the sensors have been tested in a limited water depth and low-pressure range (usually <10 kPa) [32]. An array of solid PDMS based capacitive pressure sensing system is another example that displays excellent performance in deep sea-water [33].…”

Recent Progress in Flexible Pressure Sensor Arrays

“…Using a porous elastomer as the dielectric layer can effectively improve the sensitivity of capacitive pressure sensors by expelling air from the porous elastomer during compression [ 37 ]. The structure of the porous elastomer can increase the compressibility of the dielectric layer and make the dielectric layer easier to deform.…”