Quick Thermal Response‐Transparent‐Wearable Heater Based on Copper Mesh/Poly(Vinyl Alcohol) Film

Abstract

High‐performance, transparent, wearable heaters with fast thermal response are developed. To accomplish this, highly conductive and transparent copper (Cu) mesh films are transfer printed onto flexible poly(vinyl alcohol) (PVA) substrates of different thicknesses. The thermal response characteristics of the heaters, with different PVA substrate thicknesses, are analyzed and results are recorded. The Cu mesh/PVA film heater shows a favorable figure of merit value of 228.4 and outstanding durability in response to mechanical stress tests for bending, crumpling, and detaching. Through the test results, it is concluded that the thermal response time of the heater is directly related to the thickness of the PVA substrate. The optimized Cu mesh/PVA film heater, with a substrate thickness of ≈60 μm and input voltage of 3 V (DC), exhibits a fast Joule heating effect with a response time of ≈12 s and a ramping rate of ≈7.5 °C s−1. These are excellent results, compared with the previously reported studies with other metal‐based flexible transparent heaters. A flexible transparent heater with low applied voltage and fast response time is expected to have innovative electrothermal applications, such as transparent soft actuators, wearable heaters, and medical thermotherapy pads.

Room Temperature Curable Copper Nanowire-Based Transparent Heater

“…For heater applications, TCFs with sheet resistance less than 10 Ω/sq. have been shown to be suitable, with a good response time at low voltages. − Figure reveals how the sheet resistance of the Cu NW film decreases with increasing number of spin coating cycles on glass and PET substrates. This is because with an increase in the number of cycles the amount of Cu on the substrate also increases.…”

Copper micromesh-based lightweight transparent conductor with short response time for wearable heaters

“…Transparent heaters (THs) have been studied for multiple potential applications, including smart windows [1,2], defrosters [3,4], thermochromic displays [5,6], physical/ chemical sensors [7,8], and other advanced heat-generating systems [9][10][11]. High optical transparency and excellent electrical conductivity are two important factors for high-performance THs.…”

“…Moreover, this technology is being mainly developed based on the research results of existing transparent conductors with transparent conductive oxides (TCOs), such as indium tin oxide (ITO) and fluorine-doped tin oxide (FTO) films [12]. However, owing to their brittle nature, it is extremely difficult to adapt TCO films in the development of next-generation transparent conductors for flexible/wearable TH applications [11]. Thus, there has been active research on the replacement of commercial TCO films for flexible/wearable THs.…”

“…Conductive polymers, such as poly(3,4-ethylen edioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), have outstanding advantages in terms of mechanical flexibility and solution processibility; however, conductive polymers have low electrical conductivity, and poor stability against heat and moisture, thereby limiting their application in high-performance optoelectronic devices [17,18]. Meanwhile, carbon nanomaterials, such as graphene and carbon nanotubes, have excellent thermal conductivity and flexibility; however, the manufacturing costs for high-quality carbon-based nanomaterials through thermal and plasma chemical vapor deposition techniques are usually expensive [11,19]. Accordingly, owing to their relatively simple manufacturing process (high productivity) and superior physical properties, such as optical/electrical conductance and mechanical flexibility, the development of metal-based flexible THs with metal nanowires (NWs) and mesh structures have recently garnered considerable attention as an alternative to commercial TCO films [3,4,9,20].…”

Metallic Micro‐Nano Network‐Based Soft Transparent Electrodes: Materials, Processes, and Applications

“…c) Top: photograph (left) and optical micrograph (right) of the Cu mesh/PVA film; bottom: Temperature profiles of the Cu mesh/PVA thermotherapy pad at different input voltages (left) and IR thermal image and photograph of the Cu mesh/PVA heater attached to a finger (right). Reproduced with permission [187]. Copyright 2021, Wiley-VCH GmbH.…”