The medical field will require smaller and more complex microrobots to better target drug delivery, assist in fertilization, and conduct biopsies. The nanobots, however, are difficult to make and require a precise, labor-intensive manufacturing process.
In addition to a steady hand, a microrobot maker has traditionally needed needle-nosed tweezers, a microscope, and at least eight hours.
With the help of magnets and a 3D printer, University of Toronto engineers want to speed up the process – to 20 minutes.
Each microrobot is the size of a pin head, and built by carefully arranging microscopic sections of magnetic needles atop a flat, flexible material. Once deployed, the researchers apply magnetic fields to induce the microrobots to squirm through fluid channels, or close their tiny mechanical 'jaws' to take a tissue sample.
"If we were taking samples in the urinary tract or within fluid cavities of the brain, we envision that an optimized technique would be instrumental in scaling down surgical robotic tools," said the lab’s lead researcher Professor Eric Diller .
To demonstrate their new technique, the researchers devised more than 20 different robotic shapes, which were then programmed into a 3D printer. The printer built the microrobot as designed, orienting the magnetically patterned particles as part of the process.
"Previously, we would prepare one shape and manually design it, spend weeks planning it, before we could fabricate it. And that's just one shape," said Diller. "Then when we build it, we would inevitably discover specific quirks – for example, we might have to tweak it to be a little bigger or thinner to make it work."
Cutting out those early steps, Diller and his team have developed a simplified, just-click-print approach that allows the consideration of a variety of designs.
In an interview with Tech Briefs, Diller explains how the automated assembly process will open the door for even smaller, even more complex microrobots.
Tech Briefs: What inspired this idea?
Prof. Eric Diller: Our previous work focused on manual assembly of microrobots using tweezers under a microscope. We took inspiration from 3D printers which can pattern any shape automatically in a precise and fast way. Our challenge was to adapt the operation of a 3D printer to simultaneously print and program the magnetization profile within the microrobot.
Tech Briefs: Are you truly able to program the shapes and click print? How simple is the method?
Diller: We design the microrobot shape using computer modelling software, which we then send to our new magnetic printing machine. This machine then forms the shapes of the microrobot similar to how a 3D printer works, but while also programming a magnetic pattern into the microrobot. Just like a 3D printer, our machine prints thin layers one at a time.
Tech Briefs: What kinds of shapes are possible?
Diller: Any thin shapes are possible, and in our recent paper we show 14 different flat shapes such as multi-arm grippers, 8-legged crawling robots, and folding rings. Because the technology is easy and quick to use, we can iterate on our design, tweaking the size and shape to refine the performance of the microrobot.
Tech Briefs: What are the most challenging aspects of manual assembly of microrobots?
Diller: Manually assembling microrobots requires fine dexterity, a steady hand, and lots of time. Just assembling the many blocks of a microrobot using tweezers and glue required many hours. Each block must be custom made itself, which involved many precision steps over several days. There were many chances for errors, the minimum size was limited to building blocks 1/2-mm in size, and the slow [pace] impeded the design process.
Tech Briefs: What are the most exciting applications to you with these kinds of self-assembled robots?
Diller: We plan to adapt the gripping microrobots shown in our recent work to take biopsy samples inside the human body. We are also modifying the design into swallow-able capsules for collecting samples inside the stomach and small intestine, and to use as surgical tools.
Tech Briefs: What’s next regarding this work?
Diller: We're working to upgrade our printing machine to make fully 3D shapes rather than the mostly flat designs we've shown here. This will allow us to develop more complex microrobots with richer functions. We are also exploring different magnetic materials to use in our microrobots for biomedical applications because the rare-earth magnets used here are not biocompatible. Finally, we are working on the use of medical imaging, such as ultrasound, to observe the motion of microrobots inside the body. This will allow us to track and operate the microrobots when we can't see them directly.
What do you think? Share your comments and questions below.
Transcript
00:00:00 These are magnetic microrobots, just millimeters in size. They bend and move in response to applied magnetic fields And with these magnetic fields controlled by a gaming controller the micro robots can be driven carefully and precisely. They can turn by changing the direction of the magnetic field. Roll in a rotating field And even grasp and jump It often feels like you're playing a video game.
00:00:49 In some previous work I did as a demonstration I was pushing blocks of material around and using a micro robot like a bulldozer. And the demonstration I did was playing Tetris. The idea is this technique could be used to assemble human organ tissues by arranging blocks of different types of cells in particular patterns. The way these scientists actually fabricate the micro robots is pretty ingenious. Tiny rare earth magnets are magnetized in a strong magnetic field. Then they're mixed into a UV resin that will harden when exposed to UV light. The mixture is poured into a mold and placed on a stage below which is a rotatable permanent magnet.
00:01:35 This creates an adjustable magnetic field to which all the tiny magnets in the resin align. When the desired orientation is reached UV light cures the resin in one particular spot locking those magnets in place. Then the magnetic field can be adjusted and the next section cured. Ultimately the result is a flexible device with imbedded magnets that have different orientations depending on where they are. This pattern of orientations is what gives these micro robots their unique behavior in response to magnetic fields. If we can point multiple compass needles in opposite directions within a flexible device,
00:02:11 if we apply the field vertically those compass needles will both try to orient and align with that applied field. With the right magnetic fields the results can be pretty sophisticated. Watch this micro robot pick up a block and then roll with it over to a ramp. It rolls up the ramp, deposits the block at the top, and then returns to its original position. The idea is that devices like this could be used in medical applications.
00:02:45 So this could be sending a device into fluid areas in your body or into your gastrointestinal tract. For example a capsule that you could swallow which will go passively through your GI tract, have no wires attached and at the right moment we can activate a sampling chamber basically to open up and take samples of either stomach or small intestine contents, take biopsy samples of the intestinal wall. But grippers like these may not be the only magnetic microrobots invading your body. A different research group has pioneered these even smaller peanut-shaped magnetic particles.
00:03:22 And under the right magnetic field conditions they form swarms. This warm can take on different configurations: the vortex, where many particles travel together like a school of fish, the chain, where particles line up and travel single-file. And the ribbon, where motion is perpendicular to the line of particles. One potential application of micro robotic swarms is drug delivery. Each magnetic particle could carry a small amount of drug and be guided toward the intended drug delivery site. So to make a swarm useful for essential biomedical applications, you'd like to keep the swarm aggregated.
00:04:03 You probably will not be able to see single micrometer sized particles but you could see the entire swarm. So you'd like to keep it aggregated so you can move it and keep track. But then going through tight environments, for example going through blood vessels if your swarm, the overall swarm size is bigger than the blood vessel then it doesn't fit so you need to line them up and squeeze through so that's the motivation for being able to control the shape of the swarm. And, who knows, one day you might have swarms of magnetic microrobots cleaning your teeth.
00:04:34 another group of researchers has used tiny magnetic robots to clear biofilms - those are communities of bacteria and the protective sugar polymers around them. They typically build up on medical devices, the insides of pipes, and on teeth. Can I ask, does this idea of magnetic control of micro robots, does it supplant previous concepts? Like I'm trying to conceptualize this in terms of like you know sci-fi futures with nanobots where I imagine you know we imagine these things as really self-contained and you know powering themselves around the body and that sort of stuff. Yeah, great question. So the advantage of magnetic fields is that it's a very
00:05:16 scalable technique. So we can make magnetic microbots that are single cell size and we can make them that are centimeters in size and the principles behave similarly. It pulls off a lot of the functionality to off-board magnetic coils. We can have a big computer sitting there and power supply It's a lot of the hard aspects of driving a robot we can do as traditional size. You can have a big computer We can have medical imaging hooked up and do all these things off board and then on board we're just transmitting the magnetic field directly to the device and so this our micro robot is
00:05:53 basically then just like the mechanical hand of the robot and the rest of the robot is really sitting on the table beside the patient. Hey this episode of Veritasium is supported by viewers like you on Patreon and by Audible. There's no better place to listen. Listening makes us smarter, more connected people. And there's no better time to start listening than right now with a 30-day trial and your first audiobook plus two Audible originals free when you go to audible.com slash veritasium or text veritasium that's V E R I T A S I U M to 500 500. Now if you're looking for something good to listen to might I recommend "How to Change Your Mind: What the new science of psychedelics teaches
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