Medical Microrobot-Wireless Manipulation of a Drug Delivery Carrier through an External Ultrasonic Actuation: Preliminary Results

To achieve precise and untethered clinical therapeutics, microrobots have been widely researched. However, because conventional microrobot actuation is based on magnetic forces generated by a magnetic field and magnetic particles, unexpected side effects caused by additional magnetic ingredients could induce clinical safety issues. In this paper, as an alternative to an untethered actuator, we present a novel ultrasonic actuation mechanism that enables drug particle/cell manipulation and micro/nano-robot actuation in clinical biology and medicine. Firstly, characteristics of the acoustic field in the vessel mimic circular tube, formed from particles emerging through a submerged ultrasonic transducer, are mathematically analyzed and modeled. Thereafter, a control method is proposed for trapping and moving the micro-particles by using acoustic radiation force (ARF) in a standing wave of a tangential standing wave. The feasibility of the proposed method could be demonstrated with the help of experiments conducted using a single transducer with a resonance frequency of 950 kHz and a motorized linear stage, which were used in a water tank. The micro-particles in the tube were trapped via ultrasound and the position of the micro-particles could be controlled by frequency manipulation of the transducer and motor control. This study shows that ultrasonic manipulation can be used for specific applications, such as the operation of a micro robot inserted in a peripheral blood vessel and targeted for drug delivery.