Graphene field effect transistors (GFETs) are promising devices for biochemical sensing. Integrating GFETs onto
complex non-planar surfaces could uncap their potential in emerging areas of wearable electronics, such as smart
contact lenses and microneedle sensing. However, the fabrication of GFETs on non-planar surfaces is challenging
using conventional lithography approaches. Here, we develop a combined spray coating and photolithography setup
for the scalable fabrication of GFETs on non-planar surfaces and demonstrate their application as integrated GFETs on
microneedles. We optimize the setup to pattern ⇠67 µm long GFET channels across the microneedle tips. Graphene is
deposited between photo-patterned electrodes by spray coating a liquid-phase exfoliated graphene ink, while monitoring
the channel resistance to achieve the required conductivity. The successful formation of the GFET channels is confirmed
by SEM and EDX mapping, and the GFETs are shown to modulate in solution. This demonstrates an approach for the
manufacturing of graphene electronic devices on complex non-planar surfaces like microneedles and opens possibilities
for wearable GFET microneedle sensors for real-time monitoring of biomarkers.