Fabrication of interdigitated capacitor on fabric as tactile sensor

Abstract

Smart textile has opened a new paradigm of application. Therefore, interest in developing a textile-based sensor system to interact with a machine has been elevated significantly. Touch and pressure are vital interests for multipurpose use, leading to the prior work on developing textile-based sensors using embroidery, multi-layer weaving, and different printing processes. The complexity of those works requires an additional setup and machines for the application. This paper presents a novel approach to developing a low-cost and scalable tactile sensor to sense touch and conjugated pressure exerted over the fabric by means of capacitance variation using commercial stainless-steel thread and low-cost lockstitch sewing machine. The research focused on determining the distinct possibility of sensing the touch stimuli and finger pressure as the capacitance range variation and finding out the allusive structural variables of interdigitated capacitor (IDC) and parallel plate capacitor (PPC) of the sensor. For IDC, the mean capacitance variation found 1.28 pF/gm, whereas 0.81pF/gm found for the PPC structure. For both cases, 11.3 gm measured as the least possible sensing pressure. The repetitive percentage (%) of the sensor (IDC) found 97.91 after testing 1016 consecutive finger pressings cycles. The research demonstrated a circuit where the capacitance range was segmented into five slots assigning individual LEDs to sense the different ranges of touch and pressure. The capacitance range (<20pF–600pF<) facilitates the sensor to use in touch-sensitive multimodal switching and physiological monitoring where tactile information can create smart textile system intelligence.