Tensile strength and percentage elongation break testThe hydrogel patch was cut in a rectangle shape (1 × 4 cm2) and evaluated by a tensile tester (TA.XT plus, Stable Micro Systems, UK). The cross-section of the hydrogel patch was fixed by adhesive tape between the cell grips. The test conditions were the test speed of 1 mm/s and the trigger force of 5 g. Force was gradually applied until the hydrogel patch broke.
ThicknessThe thickness at five different positions on the GM hydrogel patch was measured using an analog thickness gauge.
Physical characteristicsThe color of the GM hydrogel patch was measured using Chroma Meter CR-400 (Konica Minolta, Japan). The CIE L* a* b* (L, lightness; a, redness; and b, yellowness) were determined.
Surface morphologyThe surface morphology of the GM hydrogel patch and blank-hydrogel patch were studied. All samples were incubated at 40 °C for 72 h to remove the moisture before testing. The dried samples were coated with gold (QUORUM Q150R ES, UK) and evaluated with a field emission scanning electron microscope (FE-SEM; JEOL JSM7800F, Japan) and imaged at an acceleration voltage of 5 kV.