Flexible Power Fabrics Made of Carbon Nanotubes for Harvesting Thermoelectricity

Abstract

Thermoelectric energy conversion is very effective in capturing low-grade waste heat to supply electricity particularly to small devices such as sensors, wireless communication units, and wearable electronics. Conventional thermoelectric materials, however, are often inadequately brittle, expensive, toxic, and heavy. We developed both p- and n-type fabric-like flexible lightweight materials by functionalizing the large surfaces and junctions in carbon nanotube (CNT) mats. The poor thermopower and only p-type characteristics of typical CNTs have been converted into both p- and n-type with high thermopower. The changes in the electronic band diagrams of the CNTs were experimentally investigated, elucidating the carrier type and relatively large thermopower values. With our optimized device design to maximally utilize temperature gradients, an electrochromic glucose sensor was successfully operated without batteries or external power supplies, demonstrating self-powering capability. While our fundamental study provides a method of tailoring electronic transport properties, our device-level integration shows the feasibility of harvesting electrical energy by attaching the device to even curved surfaces like human bodies.

Monitoring of Vital Signs with Flexible and Wearable Medical Devices

“…While the state-of-the-art thermoelectric generators rely on rigid, brittle, and expensive Bi 2 Te 3 and Sb 2 Te 3 -based inorganic materials, there has been a great deal of effort recently toward fl exible and lower-cost thermoelectric generators. [ 143 ] This has been accomplished by printing [ 164,[177][178][179] or sputtering [ 180 ] fi lms of the Bi 2 Te 3 and Sb 2 Te 3 materials on fl exible substrates, infi ltrating the fi lms with PEDOT:PSS to improve fl exibility, [ 181 ] and employing alternative materials with higher fl exibility such as carbon nanotubes, [ 182,183 ] PEDOT:PSS, [ 184,185 ] and Te nanorods. [ 186 ] Figure 14 b-c shows the fl exible Bi 2 Te 3 /Sb 2 Te 3 thermoelectric generator on a glass fabric developed by Kim et al (Figure 14 b), generating electricity from the heat of a person's wrist (Figure 14 c).…”

Photoinduced p‐ to n‐type Switching in Thermoelectric Polymer‐Carbon Nanotube Composites

“…Another promising n-type material are CNTs, which are intrinsically ambipolar when protected from air, and have been shown to work as both p-type and n-type thermoelectric materials. [25][26][27][28][29] Their doping level, and concomitant Seebeck coeffi cient, can be tuned by doping electrically [ 30 ] or chemically with a variety of air-stable compounds. [ 31 ] Pure CNTs exhibit, however, a high thermal conductivity [ 32 ] and are difficult to process from solution.…”

Roll type conducting polymer legs for rigid-flexible thermoelectric generator

“…P max linearly increased as ∆T (Figure 3(a)) and reached 160 nW under a ∆T of 10 K. Although there are several types of flexible TEGs known, such as single wall carbon nanotubes (SWNTs) and film type Bi 2 Te 3 , the integration of thermocouples is low (m = 4 or 6) in SWNT based TEGs 12,13 and is very high (∆T > 50 K) to reach high output in Bi 2 Te 3 . 14 As compared in Table I with the TE modules consisting of CPs or carbon nanotubes (CNTs), [15][16][17][18] the 36-couple RF-TEG module in this work shows high output in a very low ∆T and unit output in pW/K/thermocouple (Table I). As described above, the RF-TEG is bendable and the internal resistance change by the bending radius of the 36-couple RF-TEG was negligible up to a 4 cm radius of the module's curvature (Figure 3(b)), indicating that it can be easily worn on the human wrist.…”