Multimodal Neurotransmitter Image Sensor with Lateral Ion Diffusion Suppressor

In this study, we developed a CMOS-based ion image sensor to observe the dynamic behavior of biological ions in high spatial resolution. It detects H ⁺ ions produced by enzymatic reactions of neurotransmitters released from living cells, thereby capturing the neurotransmitter distribution. Previously, we fabricated a multimodal neurotransmitter image sensor to visualize acetylcholine and adenosine triphosphate by employing enzyme membrane (AChE and apyrase, respectively) coating. However, the H ⁺ ions diffuse into the buffer solution, thus reducing spatial resolution. To solve this problem, we fabricated ion diffusion suppressors on the enzyme membrane-coated sensors ( $16-64\ \mu\mathrm{m}$ pitch) and demonstrated their effectiveness.