Microstructured Porous Pyramid-Based Ultrahigh Sensitive Pressure Sensor Insensitive to Strain and Temperature

Abstract

An ultrahigh sensitive capacitive pressure sensor based on a porous pyramid dielectric layer (PPDL) is reported. Compared to that of the conventional pyramid dielectric layer, the sensitivity was drastically increased to 44.5 kPa −1 in the pressure range <100 Pa, an unprecedented sensitivity for capacitive pressure sensors. The enhanced sensitivity is attributed to a lower compressive modulus and larger change in an effective dielectric constant under pressure. By placing the pressure sensors on islands of hard elastomer embedded in a soft elastomer substrate, the sensors exhibited insensitivity to strain. The pressure sensors were also nonresponsive to temperature. Finally, a contact resistance-based pressure sensor is also demonstrated by chemically grafting PPDL with a conductive polymer, which also showed drastically enhanced sensitivity.

Soft Electronics for the Skin: From Health Monitors to Human–Machine Interfaces

“…, where A is the overlapping area of the two parallel plates, ε 0 is the permittivity of a vacuum, ε r is the relative permittivity of the elastomeric dielectric materials between the parallel plates, and d is the separation between the parallel plates. The advantages of the piezocapacitive pressure sensors include low insensitivity to temperature and humidity change, [133] low-power consumption, [114,141] low detection limit, [111,112] and high sensitivity. [111,113] However, piezocapacitive pressure sensors have a relatively small linear dynamic range [142,143] and can be disturbed by electromagnetic interference and parasitically coupled to the surroundings.…”

Transduction Mechanisms, Micro-Structuring Techniques, and Applications of Electronic Skin Pressure Sensors: A Review of Recent Advances

“…To obtain astrain-insensitive matrix of capacitive sensors, the group of Steve Park explored the strategy of harder sensitive islands, made of PDMS, embedded in a softer elastomeric substrate of ecoflex, with an elastic modulus almost 40 times smaller than that of PDMS [ 85 ]. The dielectric layer was a set of porous PDMS micro-pyramids, whose holes were produced by sacrificial polystyrene spheres, as Figure 4 b shows [ 85 ]. When the matrix was subjected to a strain of 50%, ecoflex concentrated a strain of 105.7%, while the PDMS islands only suffered a strain of 5.2% [ 85 ].…”

“…The dielectric layer was a set of porous PDMS micro-pyramids, whose holes were produced by sacrificial polystyrene spheres, as Figure 4 b shows [ 85 ]. When the matrix was subjected to a strain of 50%, ecoflex concentrated a strain of 105.7%, while the PDMS islands only suffered a strain of 5.2% [ 85 ].…”

“… Capacitive e-skin sensors, developed by ( a ) Zhenan Bao and co-workers in 2013 [ 30 ] (Copyright © 2020, Springer Nature), ( b ) Steve Park and co-workers in 2019 (reprinted with permission from [ 85 ]. Copyright 2019 American Chemical Society, Washington, WA, USA), and ( c ) Run-Wei Li and co-workers in 2020 [ 86 ] (Copyright © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany).…”

Multidirectional Cylindrical Piezoelectric Force Sensor: Design and Experimental Validation

“…Furthermore, many studies have been conducted to apply specific structures to these materials for more efficient force sensing. For example, many studies have been conducted to improve the performance of the sensor by applying various shapes, such as pyramids [ 31 ], domes, pillars [ 32 ], and springs [ 33 ], to resistive materials. However, the most common design concept of piezoelectric force sensors includes assembling a bump structure from a flat- or micro-pillar-shaped piezoelectric structure or to use electrodes of specific shapes [ 29 , 34 , 35 ].…”