凯发

Graphene, a single layer or few layers of carbon atoms tightly packed into a two-dimensional (2D) honeycomb lattice, has attracted a tremendous amount of attention and research focus since it was successfully exfoliated from highly oriented pyrolytic graphite (HOPG)[1,2]. The exceptional properties of graphene, such as ultra-high electrical conductivity, excellent thermal stability, and outstanding mechanical properties make graphene a promising material for many potential applications[3–5], including next generation ultra-compact computers, flat screen displays, conducting plastics or ceramics, micro-electro-mechanical devices and highly sensitive sensors[6–9]. 

Wearable sensors have attracted increasingly attentions due to its important role in our daily life, such as monitoring heartbeat, blood pressure, movement and temperature. Wearable sensors require that the whole electronic device should be flexible, highly sensitive and transparent. Graphene is a flexible and transparent film with high conductivity. All the merits make graphene be an excellent candidate of wearable sensors. However, the perfect graphene film without defects can barely be used in sensors, due to the uncontrollable carrier mobility. Normally, some specific patterns and defects should be created artificially. Meanwhile, direct growth and patterning of graphene can be easily realized by laser processing, which has such advantages as precise energy control capability and direct and rapid manufacturing. The main advancements in this area include laser exfoliation of HOPG [10], laser-assisted epitaxial growth [11], laser-induced CVD [12, 13], laser reduction of GO [14-16], and laser induced unzipping of carbon nanotube [17]. Patterning of graphene can be easily realized by laser processing [13-16].

Here, we offer a novel approach to integrate graphene sensors by ultrashort-pulse laser patterning on flexible and transparent substrate. Considering the application of wearable device, PDMS is chosen as the substrate, due to its flexible and transparent property. Picosecond (ps) and femtosecond (fs) lasers are appropriate for micromachining, especially offering high-quality graphene nanoribbon. The as-grown graphene film was transferred to PDMS, and then we employed ps or fs lasers to pattern graphene. Fig. 1 shows the images of patterned graphene films. The whole process is conducted in atmosphere and it is applicable for graphene films on flexible and transparent substrates. This method provides many advantages such as one-step process, non-contact operation, highly-efficiency, and environment-friendly, which is a novel yet simple method of laser micromachining. Any specific patterns designed by computer aided design (CAD) software can be fabricated directly on substrates without additional mask or setup. The merits of this method will enable its potential applications in wearable graphene-based sensors.