Honeycomb meshed working electrodes based on microsphere lithography for high-resolution chemical image sensor

Highlights: • Honeycomb meshed metal array as working electrodes of sensor is proposed. • Mesh holes and the meshed working electrodes are illuminated by the focused light spot with different sizes. • Enhanced recombination of the photo-generated holes by electrons during the initial stage of lateral diffusion. • Improved spatial resolution benefits from two boundary cases of modulated light illuminating meshed working electrodes. • High spatial resolution of sensor with meshed working electrodes is obtained under the illumination of smaller light spot. The chemical image sensor has attracted much attention because of its ability to visualize the spatial distribution of biochemical species in solution. However, the lateral diffusion of photo-generated carriers generated by illuminating backside of the substrate limits the spatial resolution of the sensor and the sharpness of the image. In this study, honeycomb meshed metal array based on microsphere lithography as working electrodes of the sensor is proposed. A focused light spot illuminates a plurality of periodic and ordered mesh holes and the metal electrodes adjacent to the mesh holes. For chemical imaging performance, sensors with honeycomb meshed working electrodes are developed for comparison with the sensor the flat working electrodes, and their spatial resolution is tested under the focused light spot with different sizes. Three interpretations of improved spatial resolution including enhanced recombination of the photo-generated holes by electrons during the initial stage of lateral diffusion and two boundary cases of modulated light illuminating meshed working electrodes on the substrate are elaborated. The experimental results show that the spatial resolution of sensor chips with honeycomb meshed working electrodes is better than that of the sensor with the flat working electrodes and is higher under the illumination condition of smaller light spots.