Small-scale robotics, or more often referred to as Microrobotics, has become a hot research topic in the past ten years or so. Back in 2014, when I first started my PhD, I remember it was a relatively niche research field, and we joked about that probably a single classroom could accommodate all relevant researchers in the whole world. There is no denying that we all hoped this field would grow bigger. But I think it is safe to say that its growth has surpassed our expectation. As a researcher in this field, I want to reflect on what has fueled its exponential growth and what has motivated more and more people to join us.
Microrobotics is not the best name for this field. A better one is Small-scale Robotics. People use Microrobotics to vaguely refer to any robotic devices that are dramatically smaller than conventional robots, which are mostly at centimeter and meter size scale. But within this field, we use Microrobots more specifically, referring to the ones with a characteristic length between one and a hundred microns. Correspondingly, the larger ones with a characteristic length at millimeter are termed as Millirobots. And the smaller ones with a characteristic length from one to a hundred nanometers are called Nanorobots. When we are amazed by a millirobot that is 1000 times smaller than a conventional meter-scale robot, a microbot is 1000 times smaller than a millirobot, and a nanorobot is 1000 times even smaller. The differences between these three categories of small-scale robots are huge. Simply grouping them together and referring to everything as microrobots is not the best idea, because it implicitly conceals the distinctive challenges, methodologies, and applications associated with each of them.
With the definition clarified, we can now examinate the motivation. It is almost mandatory to mention a 1966 American movie Fantastic Voyage whenever people talk about the motivations for small-scale robotics. OK, we’ve also mentioned it. Mission completed. Well, joking aside, that movie is half a century ago and it is not the only movie (we don’t mention relevant novels here for conciseness) that tells a story about downscaling people. Admittedly, it is probably the one with the most specific application of such downscaling to address a fictitious medical need. The basic idea is simple, there are some regions inside human body that conventional medical approaches cannot reach, or it is too dangerous to reach. If only we were able to downscale doctors and put them into the patient’s body, into the heart or the brain for example, to diagnose and treat the disease locally, maybe the patient could be saved? That is the same reasoning of using catheters, isn’t it? If we can access every single site inside our body, and conduct localized operations such as tissue removal, drug delivery, sampling, etc., we will surely be able to treat more diseases better. This is the premise for our following discussion.
The Healthcare Potential
The small-scale robots attract much attention for the promised capability to access hard-to-reach and constrained space inside human body, conducting medical operations at a resolution and delicacy that is unimageable before. They can navigate within our body using the natural networks of ducts and cavities, such as our blood circulation system, digestive system, urinary system, reproductive system, etc., pushing minimally invasive healthcare and precision medicine to a whole new level. This potential is just fascinating. And we are reasonably confident that this potential is true, as long as we can make it happen. Once it happens, it will become an enabling tool that unlocks tons of new possibilities in healthcare. Diseases will become less dreadful as doctors don’t need to “cut patients open” that often and implantable small-scale robots will also help diagnose diseases at an earlier stage. This promised paradigm-shifting potential in healthcare is so crucial and intriguing that I think it is the single most important motivation for the rapid advancement of small-scale robotics. At that future time when this potential is achieved, small-scale robotics may no longer survive as a research field because the maturity of the technology, but I bet most researchers in this field are more than happy to help it happen and then find other topics to work for a living.
Of course, the development of small-scale robotics will not just impact healthcare. Having a miniaturized robotic tool brings new possibilities to various fields, such as microfabrication, lab/organ-on-a-chip, environmental monitoring and remedy, deep sea/space exploration, etc. We human beings are at the meter scale. But our curiosity spans from subatomic sizes to lightyears. We have invented a library of tools to help us explore the world. Moving towards a larger size scale, we invented cars, trains, and planes to help us cover a distance that would have taken a person’s whole lifetime to travel. Similarly, moving towards a smaller size scale, we invented microscopes and micromanipulators to maneuver cells and even a single atom. Small-scale robotics is the extension of one of our greatest invention, robotics, to a smaller size scale. Simply put, whatever a conventional robot can do, we hope a small-scale robot could also do similar things, just at a smaller size scale.
It will be lying if I say I am not happy to see the prosperity of this field. But I am indeed surprised by its advancement speed. And that also raises some concerns for me. A fast uprise is often followed by a steep downturn. People are enthusiastic about it. People cannot wait to see the next-generation small-scale robot, then the next-next-generation. But things won’t just go well because we hope so. We will meet frustrations, roadblocks, and even dead ends. I am worried that such an acute interest in pushing this field forward will eventually backfire, luring researchers to quick success by not asking the inconvenient questions. In the very near future, when all low-hanging fruits have been harvested, will we be able to deliver the next milestone to keep the field afloat? Who is quietly cracking the hard nut while others are chasing the waves? I hope that, many years later when people look back, small-scale robotics is not a flash in the pan. Afterall, I’ve invested a decent amount of my life into it. I hope it goes somewhere.
by ZHANG Jiachen on 30 Oct 2022