Activation Free SAM-Assisted Silver Electroless Metallization of Textile for Strain Sensor Application

Abstract

Flexible, stretchable and wearable electronic devices are becoming moredemanding due to their facile interaction with human body. These devices can beeasily mount on clothing or directly attached onto skin. Among wearableelectronic devices, highly stretchable and sensitive strain sensors have drawn lotsof attention for monitoring human body motions. There are number ofrequirements for a high performance strain sensor including high sensitivity (i.e.,gauge factor (GF)), high stretchability, fast response, high stability and lowfabrication cost. Personal health monitoring, sport performance monitoring andhuman motion capturing for entertainment systems are the most popularapplications for a high performance strain senor.In this paper, we present a cost effective simple strain sensor fabricated throughsilver electroless metallization of commercial polyester fabric. To avoid usingSnCl2 or PdCl2 activation solutions, a silica-like layer was formed on polyesterfabric using an acetone based aminopropyltrimethoxysilane (APTMS) solutionfollowed by UV irradiation. Once the anchoring sites for later silanization weredeveloped, a toluene based solution of (3-Mercaptopropyl)trimethoxysilane(MPTMS) were used to activate the polyester fabric. Silver electrolessmetallization was carried out on activated polyester using silver nitrate salt andglucose as reducing agent. Scanning electron microscopy (SEM) and X-raydiffraction spectroscopy (XRD) were used to characterize the Ag-coated polyester.A thin silver coating (<1 μm) with uniform morphology and high purity wasdeposited on polyester. The conductive fabric was cut into strips of 5mmthickness for stretch-conductivity measurements. A micro-tensile machine withan in-situ confocal microscope was coupled with a digital multimeter (2-pointprobing) to investigate strain dependence electrical resistivity. In-situ confocalimaging was used to investigate the micromechanical mechanisms responsible forchanges in resistivity during stretching. A linear decrease in electrical resistancewas detected by stetching untill it reaches to a platu. The results of stretch–conductivitymeasurements suggest the potential application of Ag/Polyester forstrain sensors. Figure 1