High-response humidity sensor based on silicon microbridge with edge-constrained sandwich sensing structure

Silicon microbridge structures have attracted the attention of researchers in humidity sensing area owing to their small size and ease of integration with the integrated circuit (IC). However, the preparation of silicon microbridge humidity sensors with high response are still a challenge. This paper proposed a silicon microbridge humidity sensor based on an edge-constrained sandwich sensing structure, in which a graphene oxide core layer with small area was covered on the surface of the silicon bridge by a larger area of Nafion film. Due to the constraint of the peripheral edge, the swelling deformations of this sandwich structure in the vertical direction were effectively magnified during humidity detection. Hence, the proposed humidity sensor exhibited a higher humidity sensitivity (109.97 µV/%RH) compared to the silicon microbridge sensors with general sandwich sensing structure or monolayer sensing film. Meanwhile, the novel sensor also demonstrated a small humidity hysteresis and good linearity in humidity range of 11.3–97.3%.