Photoacoustic endoscopic probe based on lens scanning using a laterally tunable electrowetting liquid lens

Most existing photoacoustic endoscopies (PAEs) rely on external scanning methods, which can result in a bulky and complex probe. We propose a laterally tunable liquid lens that enables direct focal point shifting, eliminating the need for an external scanning mirror. This reduces system size and enhances endoscopic applications. Ray tracing analysis and experiments confirmed the lens's tunability, achieving 20 mm axial shifting and 4.42° lateral tilting at 45.3 V_rms. Integrated into a probe, the lens significantly improved photoacoustic imaging, yielding nearly four times the signal intensity of conventional stage scanning. Therefore, the proposed lens holds great potential for compact PAE.