High‐Performance Electrothermal Film Based on Laser‐Induced Graphene

Abstract

The flexible heaters have attracted growing interest due to their wide applications including biosensors, [1,2] gas sensors, [3] defoggers, [4] and microfluidics. [5] Generally, these electrothermal film heaters contain electrically conductive layers that operate under the principle of Joule heating. An excellent electrothermal heater requires not only fast response time, stable working temperature, and uniform temperature distribution but also flexibility, arbitrary shape, biocompatibility, and cost-effectiveness. [6] Much effort has been devoted to studying the indium tin oxide (ITO)-based heater due to its optical transparency, mechanical strength, and conductivity. [7] However, the poor ductility and fragility, long response time, and complex manufacturing processes limited its flexible usage. [8,9] Ceramic heaters were also widely investigated; one problem is that they do not work well for people with breathing problems. During the past few decades, metal nanowires (MNWs) such as silver nanowires (AgNWs), copper nanowires (CuNWs), and gold nanowires (AuNWs), have been investigated as alternative materials, due to there are many strategies that can fabricate their networks by simple drop casting, spin coating, and inkjet printing. [10][11][12][13] Nevertheless, the MNWsbased heaters may universally suffer from the exorbitant price of raw materials, [14] the potential presence of "super-Joule" heating hotspots induces local degradation, [15] relative low stability under electrical and/or thermal loading conditions, [16] and poor adhesion to substrates. [17] Moreover, the mentioned examples are based on the deposition of the self-heating layer on a substrate, which means that additional posting processes such as drying, curing, or sintering are needed. [18,19] Consequently, novel materials-based heating elements and strategies are highly required to achieve high-performance electrothermal heaters with a simple process and integration.Recently, carbon nanomaterials such as graphene have attracted much attention as heating elements due to their excellent electrical conductivity, mechanical strength, thermal properties, and biocompatibility. [20][21][22] Graphene-based heaters fabricated by chemical vapor deposition, [23] thermally reduced graphene oxide, [24] chemical reduced graphene oxide, [25] laser reduced graphene oxide, and [26] laser-induced graphene (LIG) from polymers [27] have been reported. Among them, LIG from polymers offers the idea of directly converting certain types of polyimides into graphene/graphite structures via photothermal or photochemical effects under ambient conditions. Due to the high-efficiency, low-cost, custom-designed pattern, scalable process, and one-step procedure without the transferring processes, this straightforward method of synthesizing LIG becomes a promising fabrication strategy for sensors, heaters, actuators, electromagnetic shielding, and smart devices. [6,21,[28][29][30] For LIG-based heaters, various investigations have been conducted, for example, Chen et al. propo...

Vertical‐Resolved Composition and Aggregation Gradient of Conjugated‐Polymer@Insulator‐Matrix for Transistors and Memory

“…This implies that different chains could be featured with different microscopic crystallinities/aggregations and different local electronic properties. [ 15,23–27 ] Phase separation between the different sub‐components of polymers, which also refers to microscopically chemical purification, increases the complication of the phase separation in conjugated‐polymer/insulator blends, but provides a potential method to improve the device performance and develop new devices. Effective methods are needed to induce appropriate phase separations to optimize the device construction and charge transport.…”

In Situ Electrical Contacts to Graphene by Laser Scribing

“…This makes it susceptible to detachment compared to the LIG adjacent to the substrate, leading to easy lamination or the transfer of LIG patterns , to other substrates. To address this adhesion issue, the common practice is to passivate LIG electrodes with a polymer layer. − While conducting a peeling adhesion test using acrylic adhesive tape, it was observed that our in situ LIG contacts also displayed weak adhesion to the substrate, resulting in a degradation of device performance. However, passivation applied to the LIG contact significantly improved the adhesion, ensuring consistent device performance throughout the test (Figure S4).…”

Conjugated Polymers from Direct Arylation Polycondensation of 3,4‐Difluorothiophene‐Substituted Aryls: Synthesis and Properties

“…Diketopyrrolopyrrole (DPP) and isoindigo (IID) units are well‐known building blocks for high‐mobility CPs, owing to their planar and electron‐deficient nature. [ 28–34 ] With DPP and IID derivatives as C─Br monomers and 4FBT and 4FTVT as C─H monomers, high‐mobility CPs with superior OTFT performance have been synthesized via DArP. [ 19,20,22,24,25 ] Apart from oligothiophenes such as thiophene, BT, TVT, and so on, diverse thiophene‐substituted aryls are also important building blocks of high‐mobility CPs.…”