Design of a scanning acoustic and photoacoustic microscopy system using open-source hardware and software components

Abstract

We have designed and started construction of an instrument that will be able to operate as both a scanning acoustic microscope and photoacoustic microscope. To keep costs down, we are using open-source hardware and software components wherever possible. The system is designed to scan specimens that are approximately 2 cm × 2 cm in lateral dimensions with lateral steps of 1 micron or less. When operating as a scanning acoustic microscope, the specimen will be water-coupled to a high-frequency ultrasound transducer operating in pulse-echo mode. When operating as a photoacoustic microscope, short light pulses infrared laser diode located under the specimen will generate ultrasound pulses thermoelastically, which will then be received by a confocal high-frequency transducer. In both cases, the specimen will be raster-scanned under the transducer by a moving stage. The mechanical scanning system was designed and built using a spring-loaded microscope stage, micrometers, stepper motors, a shield board used for 3D printers, an Arduino Mega microcontroller, and a Raspberry Pi 4 microcomputer. A graphical user interface has been written in Python using Tkinter to send the motion control commands to the stage. Future work will include incorporation of the laser and transducer control systems.