Fed 115

The fabric used for the study is a 100% waterproof cotton substrate with the characteristics shown in Table 1 and Table 2. This fabric has been chosen for obtaining excellent results in a previous study of screen printing silver conductors on different textile substrates [32 (link)].
A shrinkage study was carried out to determine the percentage of shrinkage of this fabric and provide a treatment that allows a 0% shrinkage for the thermal treatment of curing the silver ink and soldering. In the first process, the fabric was subjected to washing with neutral soap using six resistant cotton programs at temperatures of 90, 60, 50, 40, 30 °C, and a cold wash, with a spin cycle at 1200 rpm in all programs. The washing machine used was the model WM12E467EE (Siemens Aktiengesellschaft, Munich, Germany). In the second process, the fabric was subjected to steam ironing at 215 °C using the G9222F0 model (Rowenta Irons, Millville, NJ, USA). The third process was to introduce it into an oven FED-115 (Binder GmbH, Tuttlingen, Germany) at 130 °C for 30 min, using the same curing cycle as conductive silver inks. Finally, it was subjected to an oven temperature of 200 °C for 3 min, higher than 191 °C which is the melting point temperature of the Sn-Pb eutectic, using the same temperature cycle as the one used in a typical solder paste.

A total of 45 g of native potato starch (previously obtained by hydro extraction [19 (link)]) was dispersed in 100 mL of distilled water. The pH of the solution was adjusted to 8.5 with 0.1 M NaOH, and then 3% octenyl succinic anhydride was added. After 6 h, the pH was adjusted to 7 using citric acid. Subsequently, it was washed three times with distilled water and centrifuged (TDL-5M centrifuge, Bioridge, Shangai, China) at 3000 rpm for 10 min for a final wash with 96% ethanol. Finally, the OSA starch was dried (convection oven FED 115, Binder, Tuttlingen, Germany) at 40 °C for 12 h and sieved using the 63 µm mesh in an analytical sieve shaker (AS 200 model, Retsch, Haan, Germany) [20 (link)].

It was determined by solubilizing 2.5 g of encapsulates in 250 mL of distilled water, then stirred for 5 min until a homogeneous solution was obtained; subsequently, the supernatant was separated by centrifugation at 5000 rpm for 5 min in a CR4000R centrifuge (Centurion, Pocklington, UK). Finally, an aliquot of the supernatant was dried in a forced convection oven FED 115 (BINDER, Tuttlingen, Germany) at 105 °C for 5 h. The following equation was used for the calculation: $$\mathrm{S}=\left(\frac{{\mathrm{m}}_2}{{\mathrm{m}}_1}\right)·100,$$
where: S is the solubility percentage (%), m₁ is the initial weight of the encapsulated powder, and m₂ is the weight of the dry powder after dissolution.