Illumination-adjustable photoacoustic and harmonic ultrasound for tracking magnetically driven microrobots.

The development of microrobots for biomedical applications has enabled tasks such as targeted drug delivery, minimally invasive surgeries, and precise diagnostics. However, effective in vivo navigation and control remain challenging due to their small size and complex body environment. Photoacoustic (PA) and ultrasound (US) imaging techniques, which offer high contrast, high resolution, and deep tissue penetration, are integrated to enhance microrobot visualization and tracking. Traditional imaging systems have a narrow effective illumination area, suffer from severe reflection artifacts, and are affected by strong electromagnetic fields. To address this, we present an illumination-adjustable PA and harmonic US imaging system with a customized pushrod mechanism for real-time focus adjustment. Experiments demonstrate high-resolution imaging and accurate microrobot positioning, showcasing the potential for biomedical applications, especially in minimally invasive procedures.