Magnetic Navigation of a Rotating Colloidal Swarm Using Ultrasound Images

Microrobots are considered as promising tools for biomedical applications. However, the imaging of them becomes challenges in order to be further applied on in vivo environments. Here we report the magnetic navigation of a paramagnetic nanoparticle based swarm using ultrasound images. The swarm can be generated using simple rotating magnetic fields, resulting in a region containing particles with a high area density. Ultrasound images of the swarm shows a periodic changing of imaging contrast. The reason for such dynamic contrast has been analyzed and experimental results are presented. Moreover, this swarm exhibits enhanced ultrasound imaging in comparison to that formed by individual nanoparticles with a low area density, and the relationship between imaging contrast and area density is testified. Furthermore, the microrobotic swarm can be navigated near a solid surface at different velocities, and the imaging contrast show negligible changes. This method allows us to localize and navigate a microrobotic swarm with enhanced ultrasound imaging indicating a promising approach for imaging of microrobots.

A Magnetically-Triggered Soft Capsule for On-Demand Mucus Collection

In this work, we present a soft capsule for mucus collection in human intestine for diagnostic purpose, with reduced risk of tissue damage compared with other biopsy methods. The capsule implements passive locomotion and the sampling process is triggered by magnetic field using a permanent magnet, which is placed on the skin above the region of interest (ROI). The capsule contains a soft vacuum chamber which is sealed with wax. When magnetic field and mucus are present simultaneously, the circuit inside the capsule will be closed and nichrome wire will start to generate heat to melt the wax, and mucus will be collected into the vacuum chamber due to air pressure. Experiments on heating capability of nichrome wire, mucus collection and reliability of the capsule are conducted to validate this design.