Targeted drug delivery is a promising application of microrobots owing to the capability of the microrobots to access nearly every region of the human body through the circulatory system. Research on microrobots over the past few decades has enabled substantial advances in the design of both the untethered microrobots swimming in a biofluid and the related mechanisms to carry and release therapeutic agents in a controlled manner. This paper presents a comprehensive review of the technological state of the art in untethered microrobots for targeted drug delivery applications. First, the in vivo microrobot locomotion techniques are discussed with respect of the different types of actuation energy sources such as magnetic fields, motile microorganisms, acoustic waves, and chemical reaction, outlining the respective advantages and major limitations. Subsequently, recent progress in various technologies of microrobot-driven targeted drug delivery is surveyed deliberating on the corresponding drug manipulation mechanisms: magnetically driven, motile microorganisms-driven, acoustic-aided, and stimuli-responsive hydrogels-aided. Although most studies on microrobot-driven targeted drug delivery were carried out in vitro, few among them successfully demonstrated in vivo operations in living animals. In the concluding section, current challenges and future perspectives of the microrobot-driven targeted drug delivery technology are discussed.

This paper presents surface acoustic wave (SAW)-driven self-cleaning glass aimed at removing contaminants that occur on the surfaces of automotive sensors for autonomous driving. The proposed self-cleaning glass comprises an interdigitated transducer (IDT) patterned on top of the transparent piezoelectric substrate (LiNbO3) and a hydrophobic layer (Cytop) covering the IDT. First, the sliding angle and contact angle of a droplet on a hydrophobic layer are measured in different volumes without the application of any external forces. The experiment shows that the droplets smaller than 4 μl do not slide on the inclined surface. To investigate the effect of SAW on droplet removal, the traveled distances and speeds of droplets are measured in different volumes, viscosities, and applied voltages when the droplets are removed on the surface by the SAW operation of the fabricated self-cleaning glass. Then, it is also investigated that the motion of the droplets by SAW on the inclined substrate in the direction of gravity and the opposite direction. Quantitative tests on the droplet removal performance of the SAW-driven self-cleaning glass are carried out by analyzing captured images recorded during the droplet removal by the SAW operation. As proof of concept, the proposed self-cleaning technology is demonstrated on droplets formed on a lens surface of a camera on which the SAW device is mounted. The demonstration shows that the camera image distorted by droplets that occur on the initial glass cover of the camera module is quickly restored by the SAW operation. The proposed SAW-driven drop free glass can promptly remove various contaminants on the surface of the sensors. Hence, it can be applied not only for automotive sensors but also for outdoor security cameras for daily life safety and future industries such as smart factories and smart cities.

No abstract

No abstract