Wearable Gold Decorated Direct Laser Writing Graphene for Ultra-Minor Strains

Abstract

This paper reports a flexible and wearable piezoresistive strain sensor composed of LIG/PDMS nanocomposite. LIG was first prepared on commercial Kapton tape by CO2 laser scanning. The presence of carbon atoms and their high ratio compared to oxygen atoms were confirmed using XPS, XRD, and Raman tests. FESEM images also showed the presence of multilayer graphene sheets in a porous foam. The strain sensor was fabricated by transferring LIG to a PDMS elastic polymer substrate. This sensor exhibits high sensitivity (gauge factor in the range of 40 to 80), low hysteresis, and a wide working range. It also has a stable and fast dynamic response and provides good reversibility and repeatability. After 5000 cycles, the signal peak changed only 3%, indicating its long-term durability and stability. Au-enhanced sensors exhibit more regular response patterns than the pure LIG sensor. The gauge factor of 45.8 shows the sensor's high sensitivity at 0.001 strain, which is very high compared to most reported strain sensors. Both Au-enhanced sensors show regular response patterns even under a low strain of 0.1%. In addition to positive SNR numbers at 0.1% strain, the gauge factors of 37.7 and 45.8 were obtained for LIG obtained from Au-coated PI and Au-coated LIG, respectively, that shows both sensors have high sensitivity at deficient strains, which is very high compared to most reported strain sensors. These characteristics make the Au@LIG-based sensor a suitable candidate for measuring minor strains, such as arterial pulse and blood pressure, which have a high potential for use in tactile and wearable sensors. As a result, it is hoped that this LIG-based sensor can be developed into wearable sensor devices or electronic skin.