fig1

Figure 1. Comparisons of (A) thermopower and (B) merits between inorganic thermoelectric materials and hydrogel thermocells. The materials used in hydrogel thermocells are abundant, inexpensive, and low-toxic. Furthermore, hydrogel thermocells exhibit excellent flexibility and stretchability, which can meet the needs of flexible wearable electronics^{[33,63,65-69]}.