Highly Sensitive, Stretchable Pressure Sensor Using Blue Laser Annealed CNTs

Abstract

A piezoresistive sensor is an essential component of wearable electronics that can detect resistance changes when pressure is applied. In general, microstructures of sensing layers have been adopted as an effective approach to enhance piezoresistive performance. However, the mold-casted microstructures typically have quite a thick layer with dozens of microscales. In this paper, a carbon microstructure is formed by blue laser annealing (BLA) on a carbon nanotube (CNT) layer, which changes the surface morphology of CNTs into carbonaceous protrusions and increases its thickness more than four times compared to the as-deposited layer. Then, the pressure sensor is fabricated using a spin-coating of styrene–ethylene–butylene–styrene (SEBS) elastomer on the BLA CNTs layer. A 1.32 µm-thick pressure sensor exhibits a high sensitivity of 6.87 × 105 kPa−1, a wide sensing range of 278 Pa~40 kPa and a fast response/recovery time of 20 ms, respectively. The stability of the pressure sensor is demonstrated by the repeated loading and unloading of 20 kPa for 4000 cycles. The stretchable pressure sensor was also demonstrated using lateral CNT electrodes on SEBS surface, exhibiting stable pressure performance, with up to 20% stretching.

Recent progress in flexible micro-pressure sensors for wearable health monitoring

“…The high sensitivity was attributed to the extremely low initial current and high current under an external pressure. 138 …”

Wireless mm-Wave Chipless Pressure Sensor

“…Pressure sensors can be based on different physical phenomena such as capacitive, resistive, piezoelectric, and optical [3], [4]. In resistive ones [5], [6], the electrical resistance decreases with the pressure. Capacitive ones [7] usually consist of a dielectric placed between two electrodes.…”

Heating opaque material sheets by a blue laser

“…Blue laser is used in many applications such as annealing, drilling, cutting, welding, alloying, and others [1][2][3][4]. When a substrate surface is illuminated by a laser beam, the beam energy is partially absorbed and the substrate undergoes solid heating, melting, or evaporation depending on many parameters including the laser power and the reflexivity of substrate [1].…”

“…When a substrate surface is illuminated by a laser beam, the beam energy is partially absorbed and the substrate undergoes solid heating, melting, or evaporation depending on many parameters including the laser power and the reflexivity of substrate [1]. In wearable piezoresistive sensors for detecting pressure changes, the microstructures of sensing layers are formed by blue laser annealing on carbon nanotube layers [2]. In electronic industries, welding thin foils of the so-called difficult-to-weld metals is successfully done by using blue laser [3,4].…”