High‐Resolution Patterning and Transferring of Graphene‐Based Nanomaterials onto Tape toward Roll‐to‐Roll Production of Tape‐Based Wearable Sensors

Abstract

nonconventional substrates (e.g., paper, tape, and cloth) [7][8][9][10] have been widely utilized as the base materials of flexible electronic devices. Conductive nanomaterials, such as carbon nanotubes, metal oxide nanowires, and graphene, have also attracted considerable attention as functional materials for applications ranging from transistors, to sensors, to energy harvesting and storage devices. [11][12][13][14][15][16][17][18][19][20][21][22] Among these conductive nanomaterials, graphene plays a key role in producing next-generation sensors owing to its unique properties, including atomic thickness, large surface area, fast electron mobility, good piezoresistivity, and high mechanical flexibility. [23][24][25][26][27] As a result, integrations between flexible substrate materials and graphene-based nanomaterials have led to a variety of sensors and other electronic devices through development of novel fabrication processes, advancing emerging and significant fields such as real-time motion tracking, [28] structural and human health monitoring, [29][30][31] electronic skin sensing, [32][33][34][35][36] and humanized robotic manipulation. [37] It is well known that repeated mechanical exfoliation to peel single-or few-layer graphene from bulk graphite using sticky tape and transfer it to another surface is rather uncontrollable in terms of the number of graphene layers, location, and size of the peeled graphene. [38] Recently, graphene film electrodes at centimeter scale have been fabricated by peeling tape from a commercial graphite foil for the detection of glucose, [39] but the obtained electrodes did not have well-defined shapes or control over thickness. Physically rubbed graphene electrodes have also been produced by directly placing solid-state graphene powders at a channeled adhesive surface and then rubbing against the surface. [40] The resulting graphene patterns, however, have poor feature resolution. Photolithography-based microfabrication for graphene patterning [41][42][43][44][45][46][47][48][49] is relatively complex and requires multiple steps such as film deposition, lithography, and etching. Recently, various interesting methods have been developed for patterning and transferring graphene-based materials onto different substrates. For example, laser printing of graphene has been studied with variable laser energy, spot size, and pulse duration. [50][51][52][53][54] This method, however, requires sophisticated lasers and is limited to producing patterns with minimum feature size of several tens of micrometers. An ink-jet printing This paper reports on a simple and versatile method for patterning and transferring graphene-based nanomaterials onto various types of tape to realize flexible microscale sensors. The method involves drop-casting a graphene film on a prepatterned polydimethylsiloxane (PDMS) surface containing negative features by graphene suspensions, applying Scotch tape to remove the excess graphene from the nonpatterned areas of the PDMS surface, and then transferring the patte...

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