The future of micro robotics
Sergey Fatikov, a robotics specialist, professor at the University of Oldenburg, talks about various applications of micro- and nanorobots, as well as about the future of micro-robotics.
First of all, it is necessary to determine the meaning of the concept of "micro/nanorobots". Different research communities clearly have different points of view on this subject, depending on what they are working on, that is, on which robot abilities are essential for performing specific tasks.
This leads us to the basic classification in micro robotics, which is based on which of the features of micro robots is the key to performing certain tasks. On the one hand, we develop and apply robots capable of moving or moving other objects with micro/nanoscale accuracy. For example, you want to move a nanocable whose thickness is 1000 times less than the thickness of a human hair. Or you want to inject into a biological cell or extract something from it. In addition, you want these and other tasks to be performed automatically and without exhausting manual control, as happens with robots involved in industrial production. This kind of task is facing high-precision micro robotics.
On the other hand, many researchers use micro robots where their key feature is the ability to move over long distances (of course, relative to the size of micro robots, it can be several millimeters or centimeters). Usually such robots are not manually controlled and have either an integrated control system or an external one – let's call them mobile micro-robots. Such robots can use natural ways of transportation through the human body, such as blood vessels or the gastrointestinal tract, to diagnose and treat diseases. Specifically, these technologies are part of the so-called targeted therapy.
Production of micro robots
The design of micro robots and the corresponding production methods obviously depend on the size of the parts that make up the robots, and the size, in turn, depends on their purpose. A meaningful approach to designing robots is to always start from the description of the functions produced by the robot. Such a description will naturally lead to certain limitations in the design: regarding the size of the robot, the range of its movements, the range of force, the necessary data, compatibility with environmental features, and so on. Then we should think about suitable mechanisms for actuating and collecting data, as well as about the material for the production of the robot. After we have found out all this, we can start designing a robot, focusing on modern technological capabilities.
In addition, we should think about the data that we want to receive from the robot. For example, if we need visual feedback obtained through a microscope to control a robot, then the element of the robot that we are going to track (in the case of high-precision robots, the working organ usually acts as it) should always be in the field of view of the microscope. This robot must be designed in such a way as to ensure the constant visibility of the corresponding element.
Materials and power supply
The choice of materials depends entirely on the purpose of the robots and their size. Important criteria may be, for example, the required power, range of motion, production prices or compatibility with the environment of applications. High-precision micro robots need such mechanisms of actuation that produce repeatable and controlled changes in position with extremely high resolution, up to the subnanometric level. In such cases, piezoelectric materials are usually used. They are strong, powerful and precise, and are also widely available on the market in a variety of variations.
Silicon is often an obvious solution if you need to use micro-manufacturing technologies due to the dimensional requirements of robot elements. Polysilicon electrostatic actuators in the form of combs, produced using surface microtreatment, are often used where high power is not required from robots. Another option is shape–remembering alloys, especially if your task does not require a very fast response to the actuator. In order to put the micro robot into action, various polymers can also be used. The choice of materials becomes especially difficult when micro robots function inside the human body. Biological compatibility and non–toxicity are obvious limitations, but not the only ones in this area.
Power supply is implemented in different ways depending on the size of the robots and the specifics of their purpose. Larger micro-robots resort to internal actuation systems, using, for example, the mentioned piezoelectric materials, polymers, and so on. Such robots are either connected to an electric power source or equipped with a battery. As for microswimmers – robots that function in a liquid environment – there are many other interesting options for power supply. In contrast to internal actuation, microswimmers can be controlled by remote energy sources. The most well-known approach is to use magnetic coils to power magnetic micro robots. Other options include various methods of self-feeding and energy utilization of biomaterials, such as cells and bacteria.
Application of nano/micro robots
The idea that the main field of application of micro robots is surgery, we owe to science fiction films like "Fantastic Journey" (1966, dir. Richard Fleischer). The film was shot more than fifty years ago, but there is still no technology to produce non-invasive surgery using surgical micro-robots. The professional community mainly works on applications in the field of delivery of medicines or stem cells to certain parts of the body. Another promising field of application is the tracking of chemical and physical parameters of human organs. Not only obvious pathways such as the gastrointestinal tract or circulatory system, but also the central nervous system and even the eyeball are considered as ways to move micro robots.
High–precision micro robots are created for the purposes of industrial production at various levels - from experimental research and rapid prototyping to automated high-performance processing. In addition to direct production, this process includes the compilation of mechanical and electrical descriptions, as well as measurements of the micro- and nanoscale object. Micro/nanointegration or multilevel production are widely discussed methods of commercialization of nanotechnology. One of the key challenges here is, for example, the question of how to integrate nanocomponents into microchips in order to increase the performance of chips.
Challenges and development prospects
Microlevel objects are governed by forces and laws that are very different from those we have at the macro level. The main problem is that we still do not fully understand the mechanisms that affect these objects, so basic research on these phenomena seems inevitable. A serious challenge in using mobile micro robots in targeted therapy is to achieve predictability of robot behavior and their controllability, including swarm behavior. Biocompatibility and non-toxicity have been another problem in this area for a long time.
In addition, micro-robots used for observations with both military and civilian purposes need reliable and long-term power sources. Such applications also imply serious challenges for the design of micro-robots, depending on the application environment of flying, crawling or floating micro-robots. Communication in swarms of micro robots is also a big problem in this field of use.
I am very optimistic about the future of micro robotics due to the growing number of professionals who are engaged in this discipline. Over the next few years, we will see a serious improvement in the quality of performance of micro robots and an increase in the number of startups that will use the potential of micro robotics to promote innovation. In some areas of use we will notice a gradual improvement, in some others we may encounter revolutionary breakthroughs. Canadian Professor Sylvian Martel, an old friend of mine, delivered a plenary speech at the MARSS (Manipulation, Automation and Robotics at Small Scales) conference this year, entitled: "Cancer treatment will be able to rely on medical nanorobotics earlier than we could have imagined." I notice the same optimistic attitude in other research communities studying micro-robotics. Micro robots will play a significant role in the changes that await us.
About the author:
Sergey Fatikov – Professor in the Department of Computing Science and Head of Division for Microrobotics and Control Engineering at the University of Oldenburg, Germany; Member of the Editorial Board of Jour. of Micro-Bio Robotics.
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