A Highly Sensitive Resistive Pressure Sensor Based on a Carbon Nanotube-Liquid Crystal-PDMS Composite

Abstract

Resistive pressure sensors generally employ microstructures such as pores and pyramids in the active layer or on the electrodes to reduce the Young’s modulus and improve the sensitivity. However, such pressure sensors always exhibit complex fabrication process and have difficulties in controlling the uniformity of microstructures. In this paper, we demonstrated a highly sensitive resistive pressure sensor based on a composite comprising of low-polarity liquid crystal (LPLC), multi-walled carbon nanotube (MWCNT), and polydimethylsiloxane (PDMS) elastomer. The LPLC in the PDMS forms a polymer-dispersed liquid crystal (PDLC) structure which can not only reduce the Young’s modulus but also contribute to the construction of conductive paths in the active layer. By optimizing the concentration of LC in PDMS elastomer, the resistive pressure sensor shows a high sensitivity of 5.35 kPa−1, fast response (<150 ms), and great durability. Fabrication process is also facile and the uniformity of the microstructures can be readily controlled. The pressure sensor offers great potential for applications in emerging wearable devices and electronic skins.

Flexible Sensors—From Materials to Applications

“…The various approaches in fabricating pressure sensors include resistive types [7,21,39,70,95,104,127,136,208,296,[413][414][415][416][417][418][419][420][421][422][423], capacitive types [25,71,146,303,310,321,352,[424][425][426][427], field-effect transistors [9][10][11]193,428], and the piezocapacitive and piezoelectric properties of materials [214,[429][430][431]. Pressure sensors' most important parameters are sensitivity, detection range and response time.…”

“…Recent developments in fabricating resistive pressure sensors have included the use of CNTs [417,419,420], AgNWs [95], ZnO [422], graphene [8,95,417,418] and conductive polymers [8,70,136].…”

“…Overall, this sensor offered low and high detection limits of 7 × 10 -3 kPa and 50 kPa, an average response time of 10 ms, and was tested after 5000 bending cycles. Additionally, a MWCNT-LD-PDMS composite (multi-walled carbon nanotubes, liquid crystal, PDMS) based sensor provided a sensitivity of 535 %/kPa, a upper detection limit of 80 kPa and remained operational after 5000 cycles [420].…”

Liquid Crystal Enabled Dynamic Nanodevices

“…A surface plasmon resonance (SPR) [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ] is formed when the incident electrons resonate with the vibration on the surface of metallic nanostructures, which has caused broad interest regarding novel applications [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. Researchers have shown that plasmonic crystals [ 20 , 21 ] are essential for superlenses [ 22 , 23 ], negative refraction applications [ 24 , 25 ], and ultra-large nonlinearity devices [ 26 , 27 ].…”

High-Performance Resistive Pressure Sensor Based on Elastic Composite Hydrogel of Silver Nanowires and Poly(ethylene glycol)

“…Several research groups have been utilized either polydimethylsiloxane (PDMS) or polyurethane (PU) as elastic matrices for highly sensitive, flexible pressure sensors, allowing tailoring of their shapes and structures [ 16 , 25 , 26 , 27 , 28 , 29 ]. However, elastic matrices, such as PDMS and PU, have the major limitation of poor processability (poor adhesion) originating from their low surface energies, making these polymers difficult to use in practical applications [ 30 , 31 ].…”