Kirigami‐Based Stretchable, Deformable, Ultralight Thin‐Film Thermoelectric Generator for BodyNET Application

Abstract

suitable for BodyNET applications. Consequently, it is urgent to exploit lightweight TEGs with stretching and/or deformation capability that can be suitably attached to non-planar heat source surfaces without compromising generating performance. To achieve this goal, organic thermoelectric materials [6,7] and novel thermoelectric materials such as carbon nanotubes (CNTs) [8] with high flexibility are of great potential application, while this kind of materials still suffered inferior thermoelectric properties with low figure-of-merit (ZT) value and electrical conductivity. As a result, to attain excellent output performance of flexible TEGs, the use of highperformance inorganic thermoelectric materials is a sensible solution. Nevertheless, the mechanically rigid or fragile features obstruct their applications in wearable electronics.One direct and effective solution is based on the island-bridge type electric connection to realize flexibility for rigid high-performance inorganic materials, where bulk n-type and p-type materials are integrated using wavy serpentine copper wires, [9,10] liquid metal, [11][12][13] and so on. However, the output power of TEGs is still limited by the small temperature difference between body and the ambient, which is generally about 10 °C with only 1-2 °C built on thermoelectric legs. [14] This hinders the development of wearable devices. Besides, further improvement of specific power density is of equal importance for wearable applications. Thin-film TEGs fabricated on flexible substrate with low thickness and weight can easily adhere to soft skin to harvest body heat. [15,16] Nevertheless, the heat transfer along the thermoelectric legs is commonly Thermoelectric generators (TEGs) as potential power supply have great prospects for wearable application. Nevertheless, difficulties in realizing deformability, ultralight weight, and high power density of TEGs at the same time has strongly frustrated their commercial applications to date. Herein, inspired by the art of kirigami, an innovative design to construct stretchable, deformable, ultralight 3D thin-film TEG from a 2D structure by introducing rational kirigami cuts is proposed. Meanwhile, high-performance inorganic thermoelectric films are compatibly introduced to the TEG without property degradation. In addition, the vertical heat flow is easily realized in the planar thin-film TEG, which is beneficial for the establishment of large temperature differences. The fabricated ultralight kirigami-based TEG (only 29 mg in weight), without an additional heat sink demonstrates the highest open voltage density of 6.712 V g −1 with a maximum power density of 255.395 µW g −1 at T hot = 60 °C. Moreover, the TEG exhibits excellent compliance to extreme mechanical deformation and adaptability to variety surfaces. This work provides a new design concept for deformable TEGs with promising application in a broader set of BodyNET technology.

Stretchable thermogalvanic hydrogel thermocell with record-high specific output power density enabled by ion-induced crystallization

“…With the continuous performance improvement in flexible thermoelectric (TE) materials, it is increasingly possible to develop self-powered wearable electronics by harvesting lowgrade thermal energy in the environment. [1][2][3][4][5][6][7][8][9][10][11] However, traditional semiconducting TE materials have relatively low thermopower (Seebeck coefficient) less than 200 mV K À1 , [12][13][14][15] and it is difficult to achieve a great breakthrough in TE performance due to the inherent electron transport properties. Moreover, their poor flexibility and wearability also hinder the development of self-powered wearable TE devices.…”

A biomimetic laminated strategy enabled strain-interference free and durable flexible thermistor electronics

“…In the context of substantially improving the comprehensive performance of the TES, the proposed strategy becomes more competitive to the reported structural counterparts in several key metrics including thermosensitivity, resolution, mechanical damage tolerance, durability, strain insensitivity, and generality (Fig. 5l and Supplementary Table 3 ) 6 , 12 , 42 , 43 , 45 , 46 , 62 – 64 , we foresee that this biomimetic laminated structural paradigm holds great promise and represents a credible new approach for the development of accurate and flexible thermistor electronics.…”

High Interfacial Thermal Stability of Flexible Flake-Structured Aluminum Thin-Film Electrodes for Bi2Te3-Based Thermoelectric Devices

“…More seriously, when heated at high temperature, the Cu electrode not only is easy to delaminate from the substrate but also easily diffuses into the Bi 2 Te 3 -based thermoelectric material, , resulting in the failure of the thermoelectric material and decreasing the service life of the thermoelectric device. A nickel or titanium film is usually deposited on the interface between the Cu thin-film electrode and the bismuth telluride (Bi 2 Te 3 )-based thermoelectric material as a barrier layer to address the issue of element diffusion between the electrode and the thermoelectric materials, , but it increases the complexity of the preparation process and the economic cost. Metal aluminum (Al) material has the advantages of light atomic mass, cheapness, high conductivity, and abundance in nature, which is very suitable for electrode materials.…”