Influence of Sweat on Joint and Sensor Reliability of E-Textiles

Abstract

This article addresses reliability under the sweat of interconnection techniques for the mounting surface mounted device (SMD) components and fully printed humidity sensors onto conductive stretchable textile ribbons. Samples underwent testing for the effect of ageing by artificial sweat on their electrical resistance using both alkaline and acidic artificial sweat. The best results in terms of electrical resistance change were obtained for samples soldered to the conductive fibers interwoven in the ribbon. However, this method can damage the ribbon due to the high temperature during soldering and significantly reduce the mechanical properties and flexibility of the ribbon, which can lead to a limited service life of samples. On the other hand, adhesive bonding is a very interesting alternative, where the above-mentioned properties are preserved, but there is a significant effect of sweat ageing on electrical resistance. The results of fully printed graphene-based humidity sensors show that, for the intended use of these sensors (i.e., detection of changes in moisture on the human body), usage of the samples is possible, and the samples are sufficiently reliable in the case of sweat degradation. In addition, the response of the sensor to humidity is quite high: 98% at a relative humidity of 98%.

Organometallic Magnesium Complex with Aggregation Induced Emission Properties: Synthesis, Characterization, and Fluorescent Fibers Applications

“…Sweat contains a wealth of chemical information that could potentially indicate the body's deeper biomolecular state. Normal human sweat can be divided into acid sweat and alkaline sweat and pathological changes of the human body may change the composition of the sweat [44–46] . Here, the fluorescence of Mg(DBM) 2 /alginate fibres changed in different types of sweat.…”

Characterizing the Impedance Properties of Dry E-Textile Electrodes Based on Contact Force and Perspiration

“…Perspiration or human sweat is another relevant physiological factor that affects the impedance of such contact-based textile electrodes, especially in ambulatory monitoring conditions. Perspiration is moderately acidic to mildly alkaline, with a pH typically between 5.5 and 8.0 [31]. It causes a reduction of electrode impedance in the short term by enabling better contact between the electrode and stratum corneum [14].…”

Novel SMD Component and Module Interconnection and Encapsulation Technique for Textile Substrates Using 3D Printed Polymer Materials

“…An effort has been made to transfer this technology to e-textile; however, due to textile substrate low-temperature resistance, dimension instability, large areas of character, and poor wettability, textile-based conductors create difficulties that limit the soldering in e-textile applications. There are other interconnection techniques that are more compatible with textiles (Table 2), such as sewing of electronic modules on flexible polyamide foil by conductive yarns [27,28], manual low-temperature soldering by bismuth solder [29,30], ultrasonic welding [31][32][33], resistance welding [34], and joining by conductive or nonconductive UV-cured and melt adhesives [35][36][37] conductive silver-plated hook and loop strips [25,36,38], snap fasteners [39][40][41], the 3D-printed press-fit socket using filaments filled by carbon [42], etc. However, all these techniques also have certain weaknesses, such as the instability of electrical contact resistance based on the gradual loosening of fibers of yarns of sewed contacts, increasing electrical resistance due to the silver tendency to peel off quickly out of hook and loop strips, the high electrical contact resistance of carbon-filled filaments for 3D printing, cost of adhesives, or the risk of some electrical components becoming damaged during ultrasonic welding interconnection process.…”