A high-speed, flexible-scanning chemical imaging system using a light-addressable potentiometric sensor integrated with an analog micromirror

A semiconductor-based chemical imaging sensor is a type of field-effect, label-free sensing system that can visualize a two-dimensional distribution of concentrations for specific chemical species on a sensor surface. This report presents the development of a high-speed, flexible chemical imaging sensor system using an analog micromirror as a light-addressing setup to scan the light-addressable potentiometric sensor (LAPS) surface from the underside. In the proposed system, a two-axis electrostatic comb-driven micromirror is used to control a modulated laser beam with rapid and tunable scanning capabilities. The position, X- and Y-axis step, direction of movement and speed of the moving laser spot can be arbitrarily defined using the programmed control on the angular rotation of the micromirror. A high-speed spatiotemporal recording of the change in pH at a rate of approximately 16 fps (frames per second) using backside illumination has been achieved by the current setup. In addition, a high-resolution chemical image with 200k pixels of a test pattern in a sensor area of 14.5 × 10.5 mm² was achieved within 40 s. The frequency-dependent photovoltage, photovoltage-reference bias voltage characteristics, and pH sensitivity are also demonstrated and discussed systematically for optimization.