Miniaturizing Laser‐Induced Graphene for Biosensors by Spatial Control of Initiation and Side‐Selective Microfabrication on Commercial Polymers

ABSTRACT Fabrication of porous graphene directly on polymers is crucial for many applications of flexible devices, including sensors, supercapacitors, and actuators. While printing methods can be used, they require the creation of inks followed by repeated printing steps and post‐printing annealing. Hence, the one‐step direct‐write nature of the laser‐induced graphene (LIG) process makes it an attractive alternative. Nevertheless, most previous work on LIG relied on continuous‐wave CO 2 lasers, which are largely limited to 100sµm resolution. Here, we develop a new approach that leverages a pulsed near‐infrared (NIR) laser. Since polyimide absorbs far less strongly at 1064 nm than at CO 2 laser wavelengths, LIG formation is substantially hindered. To overcome this challenge, we introduce a step of ink printing prior to laser patterning. Our approach enables fabricating lines as narrow as 40 µm on either the top or bottom surfaces. We utilize finite element modeling to explain the underlying mechanism of in situ LIG line thinning. This is critical for creating microelectrode arrays on flexible and implantable devices such as neural probes. Finally, we demonstrate high‐sensitivity electrochemical sensing of dopamine for our miniaturized LIG down to 10 nM concentration with sensitivity of 0.369 µA cm −2 nM −1 .