Giant thermopower of ionic gelatin near room temperature

Abstract

Harvesting heat from the environment into electricity has the potential to power Internet-of-things (IoT) sensors, freeing them from cables or batteries and thus making them especially useful for wearable devices. We demonstrate a giant positive thermopower of 17.0 millivolts per degree Kelvin in a flexible, quasi-solid-state, ionic thermoelectric material using synergistic thermodiffusion and thermogalvanic effects. The ionic thermoelectric material is a gelatin matrix modulated with ion providers (KCl, NaCl, and KNO3) for thermodiffusion effect and a redox couple [Fe(CN)64–/Fe(CN)63–] for thermogalvanic effect. A proof-of-concept wearable device consisting of 25 unipolar elements generated more than 2 volts and a peak power of 5 microwatts using body heat. This ionic gelatin shows promise for environmental heat-to-electric energy conversion using ions as energy carriers.

Stretchable and Transparent Ionogels with High Thermoelectric Properties

“…This is the highest thermovoltage for the stretchable ionic or electrical TE materials at ambient conditions (Figure 4b). [ 16a,17,19a,21,22,29 ] The champion thermovoltage for the WPU/EMIM:DCA‐50% ionogel can be as high as 27.3 mV K −1 . The thermovoltage of electronic TE materials including inorganic and organic materials is generally less than 100 µV K −1 .…”

“…Their Seebeck coefficient is usually less than 100 µV K −1 . [ 19 ] Recently, high thermovoltage was reported on ionic conductors. [ 20 ] Their thermovoltage originating from the thermal diffusion of ions, or so‐called Soret effect, can be higher than the electronic TE materials by 2–3 orders by magnitude.…”

“…[ 21 ] In order to have high ionic conductivity, the ionic TE materials are usually solutions or gels. [ 19a,20b,21b,22 ] Solutions or gels can have high mechanical flexibility as well. But stretchable ionic TE materials were rarely reported.…”

Bioinspired Self‐Healing Human–Machine Interactive Touch Pad with Pressure‐Sensitive Adhesiveness on Targeted Substrates

“…As one of the well-known soft materials, there are a number of efforts have been presented to use polymeric hydrogel as an efficient candidate for use in flexible electronic devices [11] with promising possibilities as flexible electrodes, [12][13][14][15] sensors, [4,[7][8][9]12,16,17] and displays [18,19] with the human body. The conductivity was achieved normally through the introduction of conductive polymers, [12,16] metal nanoparticles/nanowires, [2] carbon-based materials, [20] and soluble salt ions [21] into hydrogels. For example, Wu and co-workers reported a bioinspired hydrogel, composed of crosslinked poly(acrylic acid) and alginate chains by small calcium carbonate nanoparticles, was developed to fabricate a high sensitive, capacitive ionic skin sensor, which can sense the slightest change of pressure, such as a finger motion, a gentle touch, throat motion, and even blood pressure.…”

Tailoring P-N Conversion in All-solid-state Polymer Composites with A Record Ionic Thermopower

“…Although inorganic semiconductors 4 and semi-metals 5,6 TE materials have been gained extensive exploration, they still suffer from several obstacles, such as poor flexibility, substantial production cost, the involving of toxic/scarce raw material and low thermopower (~μV K -1 ), impeding them from largescale application [7][8][9] . Recently, high ionic thermopower or Seebeck coefficient (Si) was found in the ionic conducting polymer gels (PGs) 8,[10][11][12][13] , providing a new route to improve TE performance and make TE technology more economically for future wide-scale application.…”