Jul 18 2022

Medical Millirobots

It is a frustrating reality that much of the cool technology we read about today will not be ready for widespread use for another 20-30 years. And of course not all such technology will pan out – but even when there is a high confidence level that they will, it will likely be decades before they change our lives. The cool technology I read about in popular science magazines in the 1980s didn’t really hit until the 2000s, and the advanced medical technology I learned about in medical school in the early 1990s didn’t mature until recently. So keep that in mind as I discuss this incremental advance in medical millirobots.

A millirobot is literally a millimeter size robot. The challenge of designing robots this small is to pack into that small size significant functionality. One method of getting such small robots to do stuff is origami technology – the robots can change their shape by folding and unfolding. Shape changing can accomplish specific tasks, such as locomotion, or package delivery. The advance here is to allow the millirobot to perform several tasks at once with the same origami feature, therefore packing more functionality into a tiny space.

Here we report a magnetically actuated amphibious origami millirobot that integrates capabilities of spinning-enabled multimodal locomotion, delivery of liquid medicine, and cargo transportation with wireless operation.

These tiny robots can therefore be controlled wirelessly. Further they can move both through liquid and over solid surfaces. And finally, the shape changing can deliver a liquid to a target destination. All of this is accomplished with the same origami feature, allowing for increased function while maintaining a small size.

Why is the small size so important? As the title of this post suggests, for medical applications. This has been a trend in medicine over recent decades, the ability to create smaller and smaller instruments in order to make surgical and medical interventions less invasive, more precise, and more capable. One such advance is endoscopic surgery, where tiny cameras and instruments are placed through tiny cuts made in the skin and the surgery is completed on the video screen. These smaller incisions make for much less scaring and faster recovery time. This procedure has revolutionized some surgeries.

Another approach to using small devices to minimize the invasiveness of procedures is a small camera that can be swallowed like a pill. In then travels through the GI track, recording video the whole time, allowing for examination of the entire system with no discomfort. Endoscopic surgery requires direct physical control of the instruments. The camera pill passes through the system passively. What if we could have tiny medical instruments that are untethered and can be actively controlled? Imagine undergoing surgery by either swallowing small robots or having them injected through a needle. No incisions at all necessary. This is the goal of developing the technology of medical millirobots.

A swarm of such robots could include cameras to visualize the target and guide interventions. Other robots in the swarm could be loaded with various medications, such as antibiotics to treat infections, analgesics to reduce pain, and even coagulants to slow bleeding. Meanwhile other robots could have instruments that staple tissue closed, snip away unwanted tissue, destroy cancer or other harmful tissue, deliver therapeutic medication. Once this technology is mature (again, I’m thinking 2-3 decades) the possibilities are truly exciting.

A millirobot procedure would likely be something like this. You lay on a surgical table. Perhaps you are given some gentle anesthesia, or perhaps nothing at all. While your vitals are being monitored, you are given an injection into the relevant part of the body. The needle would likely need to be large, but not larger than current medical needles for certain procedures. The millirobots could be injected into a specific body cavity, or into the bloodstream, or even into the spinal fluid to gain access to the central nervous system. A device is placed over the relevant part of the body, necessary for remote control of the robots. Meanwhile there is a bank of monitors that receive images from the camera robots.

You may or may not feel anything as the robots do their tiny work – perhaps a tingling, or a pinching sensation. Surgeons can instruct some of the robots to release lidocaine or a similar drug at the site of action to reduce this pain. Meanwhile other robots are controlled in order to carry out the procedure. This could be killing a solid tumor, repairing a blood vessel, or repairing organ damage.

Long before these more advanced applications, I think we will see these robots used for precise drug delivery (likely the low hanging fruit). Right now most drugs are delivered to the entire body, by swallowing pills or injecting into muscle or directly into the blood stream. Essentially we bathe the entire body in a drug so that it can have its action in one location. This is crude but it mostly works. If we need to get a high concentration into one location, either for greater effectiveness or to reduce systemic side effects, then we can deliver the drug through an injection. If one joint is inflamed, for example, we can inject steroids right into the joint. We can also target drugs to gain access to parts of the body that normally would keep much of the drug out, like the central nervous system. We can, for example, deliver drugs into the intrathecal space, where the spinal fluid is.

Imagine, however, if we could deliver drugs directly to any tissue in a safe and targeted manner. If there is an abscess (a walled-off pocket of infection) inside the body, for example, a high dose of powerful antibiotics could be delivered directly into the abscess. Normally, it is very difficult to get antibiotics into abscesses because the blood supply does not have access to them. Chemotherapy could be delivered in this way directly onto a solid tumor. Drugs meant to affect a single organ can be delivered to that organ, without having to subject all the other organs to the same drug.

I give it a high probability that some version of these tiny medical robots will increasingly be used in the future. The potential benefits are simply to great and the pressure to develop this technology is therefore also great. Like many such advanced technologies, it will likely prove more tricky than we hope, but eventually the kinks will be worked out.


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