Minimally invasive surgery is increasingly used to target small lesions and a growing demand exists for miniaturized medical tools. These include microcatheters, articulated micro-forceps or tweezers to sense and actuate during precision surgery. The accurate integration and functionalization of chemical and physical sensors still remain a major challenge. In a new study on Science Robotics, Antoine Barbot and colleagues at the Institute of Medical Robotics in China and the Hamlyn Centre for Robotic Surgery in London developed a novel microrobotic platform to functionalize fibers ranging from 140 to 830 micrometers (µm). They then aligned the 2 mm x 3 mm and 200 µm-thick microbots to floating electronic circuits on a fiber using a wet transfer process.
The scientists controlled the position and orientation of the microrobots at the air-water interface using apermanent magnet. Using the nonhomogeneous magnetic field of the magnet they controlled the precise distance between the two microrobots and facilitated maneuvers of "grab and release" with floating electronic patterns. Barbot et al. proposed a model of this control process, including interactions of the microrobots through surface tension for detailed performance validation. They demonstrated a variety of example sensor embodiments on a 200 µm diameter fiber and 3-D devices.
The clinical emphasis on improved medical surveillance and diagnosis has steered the future of surgery toward precision intervention. The recent introduction of robotic tools on fibers toform fiberbots has allowed researchers to combine imaging, sensing and micromanipulation within a single fiber. Sophisticated microgrippers can be directly engineered on the tip of a fiber using two-photon polymerization. Researchers can establish microactuation using hydraulic links that leverage microcapillary function to use the device for targeted drug delivery and focused energy such as laser ablation. Optical fibers are a versatile substrate to develop flexible microtools. Their surfaces provide an ideal location to include multiple sensors along its length.
However, the direct patterning of microelectronics onto small, curved objects used for clinical applications is challenging, since existing microfabrication processes are primarily tailored to flat substrates. Researchers have hitherto used two main transfer methods; including dry transfer and the wet transfer technique. Dry transfer typically offers better cleanliness and higher precision compared to wet transfer due to the absence of wet etchant and fluid perturbation. Wet transfer techniques likely to occur at surgical interventions are limited by difficulties of accurately positioning and scooping floating devices. This is due to a lack of precision tools or robotic platforms for a precise practical approach. Microrobot manipulators can therefore address some of the major issues faced by manual wet transfer methods.
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