Figure 7 The output
voltage and current of the organohydrogelthermocell during deformation:
(a) The voltage-time (blue) and current-time (red)curves of the
organohydrogelthermocell being repeatedly pressed when Tc = 20 °C and Th
= 30 °C. (b) The voltage-time (blue) and current-time (red)curves of the
organohydrogelthermocell being repeatedly pressed when Tc = −20 °C and
Th = 20 °C. (c) A photograph of the organohydrogel thermocell being
pressed on an ice surface of −20 °C. Reproduced with permission from Gao
et al. Copyright 2021, Wiley-VCH.[48] (d)
Thermogravimetric characterization of BC, BC-TGC, and BC-TGC with
different LiBr weight fractions. (e) Schematic of TGC used as smart
windows. (f) The corresponding voltage and temperature-time diagram of
(e). Reproduced with permission from Yin et al. Copyright 2023,
Elsevier.[97]
Gelatin, a polypeptide polymer, contains numerous polar groups such as
-COOH, -NH2, and -OH; thus, it exhibits strong
polarization ability under the action of an electric
field.[49–51] Using this property, Chen et al.
developed a gelatin-based device that achieved a considerable
thermoelectric conversion effect by combining alkali metal salts with
iron-based reduction couples.[52]This device
demonstrated the ability to effectively harness energy from body heat
and achieved a high thermoelectric energy of 17.0 mV
K–1. It was noticed that the ion transport in gelatin
occurred by the thermal diffusion of KCl, NaCl, and
KNO3. Additionally, the thermoelectric effect was
increased by the presence of
[\({Fe(CN)}_{6}^{4-}\)/\({Fe(CN)}_{6}^{3-}\)]. This enhancement
enables wearable devices, utilizing body heat energy as a heat source,
to obtain a thermoelectric effect of 2 V and a maximum ΔT power
of 12.8 J m–2.