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Soft Micro Robotics

Periodic Reporting for period 3 - SOMBOT (Soft Micro Robotics)

Reporting period: 2020-10-01 to 2022-03-31

The field of Micro and Nano Robotics has made impressive strides over the past decade as researchers have created a variety of small devices capable of locomotion within liquid environments. Robust fabrication techniques have been developed, some devices have been functionalized for potential applications, and therapies are being actively considered. While excitement remains high for this field, we are facing a number of significant challenges that must be addressed headon if continued progress towards clinical relevance is to be made.

This project addresses what we consider to be primary roadblocks to be overcome. This includes the development of bioerodable and non-cytotoxic microrobots, development of autonomous devices capable of self-directed targeting, catheter-based delivery of microrobots near the target, tracking and control of swarms of devices in vivo, and the pursuit of clinically relevant therapies. As we consider these advances, it becomes clear that the field of micro and nanorobotics is moving away from hard microfabricated structures and towards soft, polymeric structures capable of shape modification induced by environmental conditions and other “smart” behaviors. Just as the field of robotics witnessed the emergence of “soft robotics” in which soft and deformable materials are used as primary structural components, the field of microrobotics is beginning to experience a move towards “soft microrobots.” Soft microrobots are made of soft, deformable materials capable of sensing and actuation and have the potential to exhibit behavioral response. As we develop more complex soft microrobots, we are poised to realize intelligent microrobots that autonomously respond to their environment to perform more complex tasks. This project aims to develop a number of fundamental technologies required for the fabrication of intelligent soft microrobots suitable for in vivo applications.
We already synthesized a highly efficient water-soluble two-photon photoinitiator (P2CK) and methacrylic anhydride modified gelatin (GelMA), which were used together as a new photoresist for direct 3D printing of soft hydrogel microrobots. Template-assisted fabrication together with infiltration of biodegradable polymers was also developed for fabrication of soft microrobots with materials that are capable of being 3D-printed. Biocompatible iron oxide nanoparticles and iron were successfully integrated with aforementioned techniques to provide motile components for the microrobots under magnetic actuation. The fabricated microrobots showed excellent biocompatibility, and can be degraded by the enzymes secreted by cells. Some of these devices were demonstrated to be able to deliver drugs efficiently or act as a shape memory stent for fetal urinary tract obstruction. We also developed actuation strategies that enable selective control of individual microrobots within a swarm, and strategies that transport microrobots along or against the flow.

We developed magnetic tools and micro-catheters for several medical applications. A magnetic needle to steer electrodes to perform Deep Brain Stimulation (DBS) was developed and tested on agar phantoms as well as pig cadaveric brains. A dedicated path-planning method to safely reach regions in the brain along curved trajectories was implemented and evaluated in simulation, showing increased safety and versatility over conventional approaches. Micro-catheters for vitreoretinal surgery including sub-retinal injections, epiretinal membrane peeling, or endolaser photocoagulation were also developed. Several strategies were considered, including the use of variable stiffness tools to increase the dexterity and reliability of our magnetic catheters. We tested these prototype concepts in phantom eyes as well as excised pig cadaveric eyes, also making use of medical imaging modalities such as OCT technology to evaluate the performance of our designs. We implemented specific models for these magnetic continuum robots, including the use of Cosserat rod models and FEM-based real-time simulations. These models and simulation frameworks are suitable both for the design of surgical simulators, and for an integration within control algorithms to steer magnetic tools in real-time within a patient body using our electroMagnetic Navigation Systems (eMNS).

A new design of eMNS was also proposed. It exhibits high performance electromagnets and has a reduced size and weight, with the idea of integrating the system within existing operating rooms. Our objective is to bring the magnetic navigation technology closer to the clinical application and foster the synergy between our researchers and the medical staff.
Our new design of electroMagnetic Navigation Systems (eMNS) is significantly smaller and lighter than existing systems. This makes it highly versatile and easy to integrate within existing operating rooms. We are already closely collaborating with medical physicians in a broad range of clinical applications. We expect to perform in vitro and vivo testing by the end of the project for applications such as neurvascular navigation for angiography and aneurysms treatment, fetal surgery, or eye surgery.
Potential medical applications of soft microrobots