Stretchable Nanolayered Thermoelectric Energy Harvester on Complex and Dynamic Surfaces

Abstract

Thermoelectric generators (TEGs) provide a unique solution for energy harvesting from waste heat, presenting a potential solution for green energy. However, traditional rigid and flexible TEGs cannot work on complex and dynamic surfaces. Here, we report a stretchable TEG (S-TEG) (over 50% stretchability of the entire device) that is geometrically suitable for various complex and dynamic surfaces of heat sources. The S-TEG consists of hot-pressed nanolayered p-(Sb2Te3) and n-(Bi2Te3)-type thermoelectric couple arrays and exploits the wavy serpentine interconnects to integrate all units. The internal resistance of a 10 × 10 array is 22 ohm, and the output power is ∼0.15 mW/cm2 at ΔT = 19 K on both developable and nondevelopable surfaces, which are much improved compared with those of existing S-TEGs. The energy harvesting of S-TEG from the dynamic surfaces of the human skin offers a potential energy solution for the wearable devices for health monitoring.

Advanced Wearable Thermocells for Body Heat Harvesting

“…[10] Among these power sources, thermoelectric generators (TEG) attached to the human body are highly attractive, as the heat continually being emitted by the body (up to 20 mW cm −2 ) enables a constant power supply, in contrast to motion-based, or solar-based energy harvesting technologies. [10][11][12][13]16,17] We have recently discussed the promising prospect of body heat harvesting in the future global market of wearable electronics and provided possible designs for a skin-conformal TEG. [10] However, the relatively low Seebeck coefficient (S e = ∆V/∆T, where ∆V is the open circuit voltage and ∆T is the temperature gradient) on the order of µV K −1 [18] and the reliance on rigid and expensive thermoelectric materials have greatly limited the practical development of TEGs for wearable applications.…”

Energy Harvesting and Storage with Soft and Stretchable Materials

“…J) Adapted with permission. [202] Copyright 2020, American Chemical Society. K) (Bottom left) Adapted with permission.…”

“…[191][192][193] Finally, several groups used integrated rigid thermoelectric legs in a flexible platform to create flexible devices. [176,[194][195][196][197][198][199][200][201][202][203] Flexible TEGs relying on the deposition of thin-film materials on flexible substrates are not stretchable since the deposited materials are rigid in nature, but can be flexible if they are thin enough. Additionally, in most cases, the temperature difference across the thin-film thermoelectric materials is small (if the heat flows through the thickness of the material), which results in low open-circuit voltage.…”

“…Since then, several studies reported various flexible TEGs incorporating rigid thermoelectric blocks. [176,[194][195][196][197][198][199][200][201][202][203] Such blocks can be interconnected using thin Cu traces. [200] Importantly, the space between the thermoelectric blocks should be electrically and thermally insulating; the latter helps to force heat to travel through the thermoelectric materials.…”

“…[176] Stretchable interconnects help to improve the durability and performance of rigid TEG materials embedded in silicone. By using spiral Cu electrodes, it is possible to create more robust interconnects to rigid materials, such as Sb 2 Te 3 and Bi 2 Te 3 embedded in a silicone platform, [202] as shown in Figure 6J. This TEG produced 1.5 W m −2 at a temperature gradient of 19 °C.…”