Keithley 2450 source meter

To assess the performance of the Alg/PAM/CMC-CH as an electrode for a wearable sensor platform, electromyogram (EMG) signal monitoring and a demonstration using an LED were performed. First, the LED demonstration proceeded via a light-emitting diodes Bulb LED Lamp, 5 mm (white color) with a basic breadboard and a Keithley 2450 source meter (Tektronix, Inc., Clackamas, OR, USA) as a power supply. Cyclic stretching was performed from 0% to 200% tensile strain at a speed of 0.3 mm/s. Second, two samples were connected to fine wire and hook-type electrodes, and the EMG signals were monitored in real time via data acquisition equipment (DAQ, PowerLab 8/35). Transparent skin patches (3M Tegaderm, Minnesota, MN, USA) were used to establish contact between the skin and electrodes with a sampling frequency of 200 kHz.

The surface morphology of the electrospun PVA nanofibers mats were examined using SEM (JSM-5300, JEOL, Tokyo, Japan). The samples prior to scanning were sputter-coated with gold, the diameters of fibers in randomly selected SEM micrographs were measured using Image-J software. The image of Ag NPs was taken by transmission electron microscopy (JEM-2100F, JEOL, Tokyo, Japan) Thermal stability was investigated through the Thermogravimetric Analyzer (TGA) using a THASS TGA 1000 instrument (KokBiR, Istanbul, Turkey) for the PVA nanofibers embedded with Ag NPs. Samples of 5 mg for each nanocomposite mat were used, and the rate of heating was 10 °C/min. The surface resistance of the Ag NPs-PVA nanocomposite mats was found through I-V characteristics using a Keithley 2450 source meter (Tektronix, Beaverton, OR, USA) along with a manual four probe station (Lucas Signatone, Gilray, CA, USA).

Stretching tests were performed to characterize the electrical performance of the stretchable surface electrodes under strain using the following protocol: A piece of a polyethylene terephthalate film was attached to the auto-stretching stage (Motorizer X-translation Stages, Jaeil Optical System) to hold both edges of the stretchable device patch. The sample was loaded onto the stretching stage and robustly fixed using tape (3M Co., Ltd.) and silicon epoxy (Sil-poxy, Smooth-On Co., Ltd.). A droplet of liquid metal (gallium indium eutectic, Sigma Aldrich) was applied to the electrode channel and contact pad, followed by wiring cables up to a measurement instrument. A source meter (Keithley 2450 SourceMeter, TEKTRONIX, Inc.) was used to measure the electrical performance of the stretchable electrodes. The resistance of the stretchable electrode was measured according to the stretching range using LabVIEW customized software (National Instrument Corp.).