Programmed microscopic carriers that are able to navigate, sense their surroundings, adapt to changing conditions, and perform a set of functions in the physiological environment will revolutionize many clinical practices. The microscopic size makes them unrivalled for accessing small, highly confined and delicate body sites, where conventional medical devices fall short without an invasive intervention. Nevertheless, realization of such aspects in both on-board, i.e., autonomous, and off-board, i.e., externally guided, approaches presents fundamental challenges concerning design, fabrication process, and encoding operational capabilities. Conventional microfabrication techniques mostly provide relatively simple structures with limited design flexibility and function. Realization of complex designs with compartmentalized functionalities in 3D is a daunting task at the micron scale. Our research focuses on the use of additive manufacturing technologies to enable complex microrobots and microactuators.
The use of magnetic fields is a prominent way of remote powering and control of medical microrobots. In contrast to other untethered power transfer alternatives, such as light and chemical fuels, magnetic fields provide a biocompatible source of energy and are able to safely and uniformly penetrate biological tissues. Catalytic microswimmers usually rely on non-biocompatible fuel sources for propulsion, and those that are moving with biocompatible fuels are unable to move inside biologically relevant ionic media. Powering with light is limited with the penetration depth, safely deliverable light intensity and the line-of-sight exposure, so it is not applicable to confined and complex in vivo environments. Using acoustic fields is a promising method for off-board propulsion and manipulation of microswimmers. However, the functional design of such a microswimmer and its application in a biological setting is currently insufficient and requires future developments. To rotate the double helix, rotating magnetic fields are needed, which then create a torque on the microswimmer through a magnetic axis defined perpendicular to the helical axis.
Biodegradability, i.e., decomposition over time as a result of the resident biological activity, is a critical aspect of microrobotic design for their safe operation in the living environment. When the prescribed task is accomplished, the safest option for removing the microrobots from the body is to expect their degradation to non-toxic, metabolized products. The use of non-degradable materials can result in serious acute and chronic toxicities, which could require surgical revision, and hence lower the overall desired benefit from the microrobot. As a result, materials that predictably degrade and disappear in a safe manner have become increasingly important for medical applications. Microrobotic systems developed so far have not tackled the issue of biodegradability, so it complicates their clinical use due to possible adverse effects in the body.