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

Abstract

Past research aimed at increasing the sensitivity of capacitive pressure sensors has mostly focused on developing dielectric layers with surface/porous structures or higher dielectric constants. However, such strategies have only been effective in improving sensitivities at low pressure ranges (e.g., up to 3 kPa). To overcome this well‐known obstacle, herein, a flexible hybrid‐response pressure sensor (HRPS) composed of an electrically conductive porous nanocomposite (PNC) laminated with an ultrathin dielectric layer is devised. Using a nickel foam template, the PNC is fabricated with carbon nanotubes (CNTs)‐doped Ecoflex to be 86% porous and electrically conductive. The PNC exhibits hybrid piezoresistive and piezocapacitive responses, resulting in significantly enhanced sensitivities (i.e., more than 400%) over wide pressure ranges, from 3.13 kPa−1 within 0–1 kPa to 0.43 kPa−1 within 30–50 kPa. The effect of the hybrid responses is differentiated from the effect of porosity or high dielectric constants by comparing the HRPS with its purely piezocapacitive counterparts. Fundamental understanding of the HRPS and the prediction of optimal CNT doping are achieved through simplified analytical models. The HRPS is able to measure pressures from as subtle as the temporal arterial pulse to as large as footsteps.

Mechanical Sensors for Cardiovascular Monitoring: From Battery-Powered to Self-Powered

“…The main flexible sensors for cardiovascular vital signs monitoring based on mechanical methods are strain sensors and pressure sensors, which can be monitored in a wearable or implantable form. Specifically, the basic sensing mechanisms of these sensors include capacitive [ 12 , 14 , 16 , 23 , 24 , 25 ], piezoresistive [ 26 ], piezoelectric [ 27 , 28 , 29 , 30 ], and triboelectric effects [ 31 , 32 , 33 ].…”

“…Resistive and capacitive sensors require an external power source for sensing, whereas piezoelectric and triboelectric sensors can convert pressure or strain directly into an electrical signal for self-powered sensing [ 22 ]. Generally, macro-/micro-/nanostructural design on the surface of these sensing materials can increase the effective contact area and force perception ability, thereby improving the sensitivity of the sensor and enabling it to sensitively detect weak external pressure changes [ 12 , 14 , 23 , 24 , 25 , 34 , 35 ].…”

Iontronic pressure sensor with ultra-board linear range and high sensitivity enabled by laser-induced gradient pyramidal structures

“…The rapid developments of exible pressure sensors have spurred new application opportunities for robotics 1 , prosthetic 2 , human-machine interface 3,4 , and health monitoring 5 . Compared with the piezoelectric and piezoresistive pressure sensors, the capacitive pressure sensor is simple in structure, highly stable with low drift, and has low power consumption 6,7 . The practical applications of capacitive pressure sensors hinge on their sensing performance especially high sensitivity and linearity over a broad range for easy signal processing 8 .…”

Wires with Continuous Sabal Leaf‐Patterned Micropores Constructed by Freeze Printing for a Wearable Sensor Responsible to Multiple Deformations

“…[11][12][13][14][15] Depending on the structure design, different deformations of the conductive component, which are stretching, compression, bending and twisting, have been realized. [5][6][7][16][17][18] However, it remains challenging to achieve all these deformations in a single structure design.Among the structural designs, porous structure has the capability to detect tensile, compressive, and torsional strains. [5][6][7]10] Due to the high porosity, porous structures can be largely compressed that they have been widely used to detect compressions.…”

“…[11][12][13][14][15] Depending on the structure design, different deformations of the conductive component, which are stretching, compression, bending and twisting, have been realized. [5][6][7][16][17][18] However, it remains challenging to achieve all these deformations in a single structure design.…”