Harvesting body heat through clay-based ionic thermoelectric devices

Area of Science:

• Materials Science
• Energy Harvesting
• Nanotechnology

Background:

• Thermoelectric (TE) devices offer direct conversion of heat to electricity but face challenges like conductivity trade-offs and high operating temperatures.
• Ionic thermoelectric (i-TE) devices, utilizing atmospheric humidity, present a viable low-temperature alternative for powering wearable electronics.
• Reconstructed clay membranes offer a novel platform for i-TE applications due to their unique nanofluidic properties.

Purpose of the Study:

• To demonstrate the potential of atomically thin, reconstructed clay membranes for harvesting electricity from body heat via the ionic thermoelectric effect.
• To investigate the ionic thermoelectric characteristics of montmorillonite clay (MMT) membranes.
• To evaluate the performance and durability of MMT-based i-TE devices under varying humidity and temperature conditions.

Main Methods:

• Preparation of nanofluidic membranes using reconstructed layers of montmorillonite clay (MMT).
• Characterization of ionic thermoelectric properties, including Seebeck coefficient (S_i) and ionic conductivity.
• Testing device performance by measuring voltage generation when applied to human skin under controlled temperature differences and relative humidity (RH).

Main Results:

• MMT membranes exhibited outstanding i-TE characteristics, with a Seebeck coefficient (S_i) up to 13.63 ± 1.13 mV K^-1 due to thermal transport of intercalating cations.
• Ionic conductivity and S_i increased with rising atmospheric humidity levels.
• The MMT membrane generated voltages up to 63 mV (ΔT = 1.8 K) at 85% RH when applied to skin, demonstrating effective body heat harvesting.
• Clay membranes showed superior thermal stability (∼200 °C for 5 min) and self-repairing capabilities compared to polymer-based devices.

Conclusions:

• Atomically thin reconstructed clay membranes are effective for harvesting electricity from body heat using the ionic thermoelectric effect.
• MMT membranes offer significant advantages, including high Seebeck coefficient, humidity-dependent performance, thermal stability, and self-repairing properties.
• These findings highlight the potential of clay-based i-TE devices for sustainable, low-temperature power sources in wearable electronics.