Microbotics#Design considerations

Microbots were born thanks to the appearance of the microcontroller in the last decade of the 20th century, and the appearance of microelectromechanical systems (MEMS) on silicon, although many microbots do not use silicon for mechanical components other than sensors. {{Anchor|national2016-01-29}}The earliest research and conceptual design of such small robots was conducted in the early 1970s in (then) classified research for U.S. intelligence agencies. Applications envisioned at that time included prisoner of war rescue assistance and electronic intercept missions. The underlying miniaturization support technologies were not fully developed at that time, so that progress in prototype development was not immediately forthcoming from this early set of calculations and concept design.{{cite journal|last=Solem|first=J. C.|year=1996|title=The application of microrobotics in warfare|journal=Los Alamos National Laboratory Technical Report LAUR-96-3067|doi=10.2172/369704|url=http://www.osti.gov/scitech/servlets/purl/369704|doi-access=free}} As of 2008, the smallest microrobots use a scratch drive actuator.{{cite news|url=http://news.duke.edu/2008/06/microrobots.html|title=Microrobotic Ballet|publisher=Duke University|date=June 2, 2008|access-date=2014-08-24|archive-url=https://web.archive.org/web/20110403132202/http://news.duke.edu/2008/06/microrobots.html|archive-date=2011-04-03|url-status=dead}}

The development of wireless connections, especially Wi-Fi (i.e. in household networks) has greatly increased the communication capacity of microbots, and consequently their ability to coordinate with other microbots to carry out more complex tasks. Indeed, much recent research has focused on microbot communication, including a 1,024 robot swarm at Harvard University that assembles itself into various shapes;{{cite news|url=https://arstechnica.com/science/2014/08/thousand-robot-swarm-assembles-itself-into-shapes/|title=Thousand-robot swarm assembles itself into shapes|first=Sabine|last=Hauert|work=Ars Technica|date=2014-08-14|access-date=2014-08-24}} and manufacturing microbots at SRI International for DARPA's "MicroFactory for Macro Products" program that can build lightweight, high-strength structures.{{cite news|url=http://io9.com/this-swarm-of-insect-inspired-microbots-is-unsettlingly-1566115702|title=This Swarm Of Insect-Inspired Microbots Is Unsettlingly Clever|work=io9|first=Ria|last=Misra|date=2014-04-22|access-date=2014-08-24}}{{cite news|url=http://recode.net/2014/04/16/sri-unveils-tiny-robots-ready-to-build-big-things/|title=SRI Unveils Tiny Robots Ready to Build Big Things|first=James|last=Temple|work=re/code|date=2014-04-16|access-date=2014-08-24|archive-url=https://archive.today/20140825084136/http://recode.net/2014/04/16/sri-unveils-tiny-robots-ready-to-build-big-things/|archive-date=2014-08-25}}

Microbots called xenobots have also been built using biological tissues instead of metal and electronics.{{cite journal |last1=Kriegman |first1=Sam |last2=Blackiston |first2=Douglas |last3=Levin |first3=Michael |last4=Bongard |first4=Josh |title=A scalable pipeline for designing reconfigurable organisms |journal=Proceedings of the National Academy of Sciences |date=2020 |volume=117 |issue=4 |pages=1853–1859|doi=10.1073/pnas.1910837117|pmid=31932426 |pmc=6994979 |bibcode=2020PNAS..117.1853K |doi-access=free }} Xenobots avoid some of the technological and environmental complications of traditional microbots as they are self-powered, biodegradable, and biocompatible.

While the "micro" prefix has been used subjectively to mean "small", standardizing on length scales avoids confusion. Thus a nanorobot would have characteristic dimensions at or below 1 micrometer, or manipulate components on the 1 to 1000 nm size range.{{Citation needed|reason=Need To Source Scientific Metrix|date=April 2020}} A microrobot would have characteristic dimensions less than 1 millimeter, a millirobot would have dimensions less than a cm, a mini-robot would have dimensions less than {{convert|10|cm|0|abbr=on}}, and a small robot would have dimensions less than {{convert|100|cm|0|abbr=on}}.{{Cite web |title=Microrobotics: Tiny Robots and Their Many Uses {{!}} Built In |url=https://builtin.com/robotics/microrobotics |access-date=2024-01-26 |website=builtin.com |language=en}}

Many sources also describe robots larger than 1 millimeter as microbots or robots larger than 1 micrometer as nanobots. {{Crossreference|See also: :Category:Micro robots}}

{{more citations needed section|date=August 2014}}

{{Anchor|motility2016-01-29}}The way microrobots move around is a function of their purpose and necessary size. At submicron sizes, the physical world demands rather bizarre ways of getting around. The Reynolds number for airborne robots is less than unity; the viscous forces dominate the inertial forces, so “flying” could use the viscosity of air, rather than Bernoulli's principle of lift. Robots moving through fluids may require rotating flagella like the motile form of E. coli. Hopping is stealthy and energy-efficient; it allows the robot to negotiate the surfaces of a variety of terrains.{{cite book|last=Solem |first=J. C.|year=1994|chapter=The motility of microrobots|title=Artificial Life III: Proceedings of the Workshop on Artificial Life, June 1992, Santa Fe, NM |series=Proceedings, Santa Fe Institute studies in the sciences of complexity|editor=Langton, C. |publisher=Santa Fe Institute Studies in the Sciences of Complexity (Addison-Wesley, Reading, MA)|volume=17|pages=359–380|url=https://searchworks.stanford.edu/view/2837765}} Pioneering calculations (Solem 1994) examined possible behaviors based on physical realities.{{cite book |last=Kristensen |first=Lars Kroll |year=2000|chapter=Aintz: A study of emergent properties in a model of ant foraging|title=Artificial Life VII: Proceedings of the Seventh International Conference on Artificial Life |editor1=Bedau, M. A. |display-editors=et al |publisher=MIT Press|pages=359|chapter-url=https://books.google.com/books?id=-xLGm7KFGy4C&q=The+%22motility+of+microrobots%22&pg=PA359|isbn=9780262522908 }}

One of the major challenges in developing a microrobot is to achieve motion using a very limited power supply. The microrobots can use a small lightweight battery source like a coin cell or can scavenge power from the surrounding environment in the form of vibration or light energy.{{cite news|url=http://inhabitat.com/swarms-of-solar-powered-microbots-may-revolutionize-data-gathering/|title=Swarms of Solar Microbots May Revolutionize Data Gathering |website=Inhabitat |first=Bridgette |last=Meinhold |date=31 August 2009}} Microrobots are also now using biological motors as power sources, such as flagellated Serratia marcescens, to draw chemical power from the surrounding fluid to actuate the robotic device. These biorobots can be directly controlled by stimuli such as chemotaxis or galvanotaxis with several control schemes available. A popular alternative to an onboard battery is to power the robots using externally induced power. Examples include the use of electromagnetic fields,{{cite news|url=http://www.phys.org/news/2019-01-smart-micro-robots.html |title=Researchers develop smart micro-robots that can adapt to their surroundings |website=Phys.org |date=January 18, 2019 |author=Ecole Polytechnique Federale de Lausanne}} ultrasound and light to activate and control micro robots.{{cite journal|last1=Chang|first1=Suk Tai|last2=Paunov|first2=Vesselin N.|last3=Petsev|first3=Dimiter N.|last4=Velev|first4=Orlin D.|title=Remotely powered self-propelling particles and micropumps based on miniature diodes|journal=Nature Materials|volume=6|issue=3|date=March 2007|pages=235–240|issn=1476-1122|doi=10.1038/nmat1843|pmid=17293850|bibcode=2007NatMa...6..235C|s2cid=20558069 }}

The 2022 study focused on a photo-biocatalytic approach for the "design of light-driven microrobots with applications in microbiology and biomedicine".{{Cite journal |last1=Villa |first1=Katherine |last2=Sopha |first2=Hanna |last3=Zelenka |first3=Jaroslav |last4=Motola |first4=Martin |last5=Dekanovsky |first5=Lukas |last6=Beketova |first6=Darya Chylii |last7=Macak |first7=Jan M. |last8=Ruml |first8=Tomáš |last9=Pumera |first9=Martin |date=2022-02-05 |title=Enzyme-Photocatalyst Tandem Microrobot Powered by Urea for Escherichia coli Biofilm Eradication |journal=Small |volume=18 |issue=36 |language=en |pages=2106612 |doi=10.1002/smll.202106612 |pmid=35122470 |issn=1613-6810|doi-access=free |hdl=10195/81003 |hdl-access=free }}{{Cite web |last=Jones |first=Nicholas |title=Revolutionizing Robotics and AGVs with Advanced Drive Control |url=https://ds200sdccg4a.com/blog |access-date=2024-01-26 |website=ds200sdccg4a.com |language=en}}{{Cite web |last1=Chemistry |first1=University of |last2=Prague |first2=Technology |title=New research into a microrobot powered by urea for E. coli biofilm eradication |url=https://phys.org/news/2022-07-microrobot-powered-urea-coli-biofilm.html |access-date=2022-07-22 |website=phys.org |language=en}}

Microrobots employ various locomotion methods to navigate through different environments, from solid surfaces to fluids. These methods are often inspired by biological systems and are designed to be effective at the micro-scale.{{Cite journal |last1=Abbott |first1=Jake J. |last2=Peyer |first2=Kathrin E. |last3=Lagomarsino |first3=Marco Cosentino |last4=Zhang |first4=Li |last5=Dong |first5=Lixin |last6=Kaliakatsos |first6=Ioannis K. |last7=Nelson |first7=Bradley J. |date=November 2009 |title=How Should Microrobots Swim? |url=http://journals.sagepub.com/doi/10.1177/0278364909341658 |journal=The International Journal of Robotics Research |language=en |publication-date=July 21, 2009 |volume=28 |issue=11–12 |pages=1434–1447 |doi=10.1177/0278364909341658 |issn=0278-3649|url-access=subscription }} Several factors need to be maximized (precision, speed, stability), and others have to be minimized (energy consumption, energy loss) in the design and operation of microrobot locomotion in order to guarantee accurate, effective, and efficient movement.{{Cite book |last=Sitti |first=Metin |title=Mobile microrobotics |date=2017 |publisher=MIT Press |isbn=978-0-262-03643-6 |series=Intelligent robotics and autonomous agents |location=Cambridge, MA}}

When describing the locomotion of microrobots, several key parameters are used to characterize and evaluate their movement, including stride length and transportation costs. A stride refers to a complete cycle of movement that includes all the steps or phases necessary for an organism or robot to move forward by repeating a specific sequence of actions. Stride length (𝞴_s) is the distance covered by a microrobot in one complete cycle of its locomotion mechanism. Cost of transport (CoT) defines the work required to move a unit of mass of a microrobot a unit of distance

Microrobots that use surface locomotion can move in a variety of ways, including walking, crawling, rolling, or jumping. These microrobots meet different challenges, such as gravity and friction. One of the parameters describing surface locomotion is the Frounde number, defined as:

$Fr=\backslash frac\{v^2\}\{g*\backslash lambda\_s\}$

Where v is motion speed, g is the gravitational field, and 𝞴s is a stride length. A microrobot demonstrating a low Froude number moves slower and more stable as gravitational forces dominate, while a high Froude number indicates that inertial forces are more significant, allowing faster and potentially less stable movement.

Crawling is one of the most typical surface locomotion types. The mechanisms employed by microrobots for crawling can differ but usually include the synchronized movement of multiple legs or appendages. The mechanism of the microrobots' movements is often inspired by animals such as insects, reptiles, and small mammals. An example of a crawling microrobot is RoBeetle. The autonomous microrobot weighs 88 milligrams (approximately the weight of three rice grains). The robot is powered by the catalytic combustion of methanol. The design relies on controllable NiTi-Pt–based catalytic artificial micromuscles with a mechanical control mechanism.{{Cite journal |last1=Yang |first1=Xiufeng |last2=Chang |first2=Longlong |last3=Pérez-Arancibia |first3=Néstor O. |date=2020-08-26 |title=An 88-milligram insect-scale autonomous crawling robot driven by a catalytic artificial muscle |url=https://www.science.org/doi/10.1126/scirobotics.aba0015 |journal=Science Robotics |language=en |volume=5 |issue=45 |doi=10.1126/scirobotics.aba0015 |pmid=33022629 |issn=2470-9476|url-access=subscription }}

Other options for actuating microrobots' surface locomotion include magnetic, electromagnetic, piezoelectric, electrostatic, and optical actuation.

Swimming microrobots are designed to operate in 3D through fluid environments, like biological fluids or water. To achieve effective movements, locomotion strategies are adopted from small aquatic animals or microorganisms, such as flagellar propulsion, pulling, chemical propulsion, jet propulsion, and tail undulation. Swimming microrobots, in order to move forward, must drive water backward.

Microrobots move in the low Reynolds number regime due to their small sizes and low operating speeds, as well as high viscosity of the fluids they navigate. At this level, viscous forces dominate over inertial forces. This requires a different approach in the design compared to swimming at the macroscale in order to achieve effective movements. The low Reynolds number also allows for accurate movements, which makes it good application in medicine, micro-manipulation tasks, and environmental monitoring.

Dominating viscous (Stokes) drag forces T_drag on the robot balances the propulsive force F_p generated by a swimming mechanism.

 $T=T\_(drag)=\backslash frac\{bv\}\{m\}$

Where b is the viscous drag coefficient, v is motion speed, and m is the body mass.

One of the examples of a swimming microrobot is a helical magnetic microrobot consisting of a spiral tail and a magnetic head body. This design is inspired by the flagellar motion of bacteria. By applying a magnetic torque to a helical microrobot within a low-intensity rotating magnetic field, the rotation can be transformed into linear motion. This conversion is highly effective in low Reynolds number environments due to the unique helical structure of the microrobot. By altering the external magnetic field, the direction of the spiral microrobot's motion can be easily reversed.{{Cite journal |last1=Liu |first1=Huibin |last2=Guo |first2=Qinghao |last3=Wang |first3=Wenhao |last4=Yu |first4=Tao |last5=Yuan |first5=Zheng |last6=Ge |first6=Zhixing |last7=Yang |first7=Wenguang |date=2023-01-01 |title=A review of magnetically driven swimming microrobots: Material selection, structure design, control method, and applications |journal=Reviews on Advanced Materials Science |language=en |volume=62 |issue=1 |page=119 |doi=10.1515/rams-2023-0119 |bibcode=2023RvAMS..62..119L |issn=1605-8127|doi-access=free }}

In the specific instance when microrobots are at the air-fluid interface, they can take advantage of surface tension and forces provided by capillary motion. At the point where air and a liquid, most often water, come together, it is possible to establish an interface capable of supporting the weight of the microrobots through the work of surface tension. Cohesion between molecules of a liquid creates surface tension, which otherwise creates ‘skin’ over the water’s surface, letting the microrobots float instead of sinking. Through such concepts, microrobots could perform specific locomotion functions, including climbing, walking, levitating, floating, and or even jumping, by exploring the characteristics of the air-fluid interface.{{Cite journal |last1=Koh |first1=Je-Sung |last2=Yang |first2=Eunjin |last3=Jung |first3=Gwang-Pil |last4=Jung |first4=Sun-Pill |last5=Son |first5=Jae Hak |last6=Lee |first6=Sang-Im |last7=Jablonski |first7=Piotr G. |last8=Wood |first8=Robert J. |last9=Kim |first9=Ho-Young |last10=Cho |first10=Kyu-Jin |date=2015-07-31 |title=Jumping on water: Surface tension–dominated jumping of water striders and robotic insects |url=https://www.science.org/doi/10.1126/science.aab1637 |journal=Science |language=en |volume=349 |issue=6247 |pages=517–521 |doi=10.1126/science.aab1637 |bibcode=2015Sci...349..517K |issn=0036-8075|url-access=subscription }}

Due to the surface tension ,σ, the buoyancy force, F_b, and the curvature force, F_c, play the most important roles, particularly in deciding whether the microrobot will float or sink on the surface of the liquid. This can be expressed as

$\backslash sigma=F\_b+F\_c$

F_b is obtained by integrating the hydrostatic pressure over the area of the body in contact with the water. In contrast, F_c is obtained by integrating the curvature pressure over this area or, alternatively, the vertical component of the surface tension, $\backslash sigma\backslash sin\backslash theta$, along the contact perimeter.{{Cite journal |last1=Hu |first1=David L. |last2=Chan |first2=Brian |last3=Bush |first3=John W. M. |date=August 2003 |title=The hydrodynamics of water strider locomotion |url=https://www.nature.com/articles/nature01793 |journal=Nature |language=en |volume=424 |issue=6949 |pages=663–666 |doi=10.1038/nature01793 |pmid=12904790 |bibcode=2003Natur.424..663H |issn=0028-0836|url-access=subscription }}

One example of a climbing, walking microrobot that utilizes air-fluid locomotion is the Harvard Ambulatory MicroRobot with Electroadhesion (HAMR-E).{{Cite journal |last1=de Rivaz |first1=Sébastien D. |last2=Goldberg |first2=Benjamin |last3=Doshi |first3=Neel |last4=Jayaram |first4=Kaushik |last5=Zhou |first5=Jack |last6=Wood |first6=Robert J. |date=2018-12-19 |title=Inverted and vertical climbing of a quadrupedal microrobot using electroadhesion |url=https://www.science.org/doi/10.1126/scirobotics.aau3038 |journal=Science Robotics |language=en |volume=3 |issue=25 |doi=10.1126/scirobotics.aau3038 |pmid=33141691 |issn=2470-9476|url-access=subscription }} The control system of HAMR-E is developed to allow the robot to function in a flexible and maneuverable manner in a challenging environment. Its features include its ability to move on horizontal, vertical, and inverted planes, which is facilitated by the electro-adhesion system. This uses electric fields to create electrostatic attraction, causing the robot to stick and move on different surfaces.{{Cite journal |last1=Rajagopalan |first1=Pandey |last2=Muthu |first2=Manikandan |last3=Liu |first3=Yulu |last4=Luo |first4=Jikui |last5=Wang |first5=Xiaozhi |last6=Wan |first6=Chaoying |date=July 2022 |title=Advancement of Electroadhesion Technology for Intelligent and Self-Reliant Robotic Applications |url=https://onlinelibrary.wiley.com/doi/10.1002/aisy.202200064 |journal=Advanced Intelligent Systems |language=en |volume=4 |issue=7 |doi=10.1002/aisy.202200064 |issn=2640-4567|doi-access=free }} With four compliant and electro-adhesion footpads, HAMR-E can safely grasp and slide over various substrate types, including glass, wood, and metal. The robot has a slim body and is fully posable, making it easy to perform complex movements and balance on any surface.

Flying microrobots are miniature robotic systems meticulously engineered to operate in the air by emulating the flight mechanisms of insects and birds. These microrobots have to overcome the issues related to lift, thrust, and movement that are challenging to accomplish at such a small scale where most aerodynamic theories must be modified. Active flight is the most energy-intensive mode of locomotion, as the microrobot must lift its body weight while propelling itself forward. To achieve this function, these microrobots mimic the movement of insect wings and generate the necessary airflow for producing lift and thrust. Miniaturized wings of the robots are actuated with Piezoelectric materials, which offer better control of wing kinematics and flight dynamics.{{Cite journal |last1=Jafferis |first1=Noah T. |last2=Helbling |first2=E. Farrell |last3=Karpelson |first3=Michael |last4=Wood |first4=Robert J. |date=June 2019 |title=Untethered flight of an insect-sized flapping-wing microscale aerial vehicle |url=https://www.nature.com/articles/s41586-019-1322-0 |journal=Nature |language=en |volume=570 |issue=7762 |pages=491–495 |doi=10.1038/s41586-019-1322-0 |pmid=31243384 |bibcode=2019Natur.570..491J |issn=1476-4687|url-access=subscription }}

To calculate the necessary aerodynamic power for maintaining a hover with flapping wings, the primary physical equation is expressed as

$mg=2*\backslash rho*l^2*\backslash phi*\backslash upsilon\_i^2$

where m is the body mass, L is the wing length, Φ represents the wing flapping amplitude in radians, ρ indicates the air density, and V_i corresponds to the induced air speed surrounding the body, a consequence of the wings' flapping and rotation movements. This equation illustrates that a small insect or robotic device must impart sufficient momentum to the surrounding air to counterbalance its own weight.{{Cite book |last1=Shyy |first1=Wei |url=https://www.cambridge.org/core/books/aerodynamics-of-low-reynolds-number-flyers/B73F3DB3BF37F6D6A76E8194CFC2F692 |title=Aerodynamics of Low Reynolds Number Flyers |last2=Lian |first2=Yongsheng |last3=Tang |first3=Jian |last4=Viieru |first4=Dragos |last5=Liu |first5=Hao |date=2007 |publisher=Cambridge University Press |isbn=978-0-521-88278-1 |series=Cambridge Aerospace Series |location=Cambridge |doi=10.1017/cbo9780511551154}}

One example of a flying microrobot that utilizes flying locomotion is the RoboBee and DelFly Nimble,{{Cite journal |last1=Wang |first1=S. |last2=den Hoed |first2=M. |last3=Hamaza |first3=S. |date=2024 |title=A Low-cost Fabrication Approach to Embody Flexible and Lightweight Strain Sensing on Flapping Wings: 2024 IEEE International Conference onRobotics and Automation |url=https://research.tudelft.nl/en/publications/a-low-cost-fabrication-approach-to-embody-flexible-and-lightweigh |journal=IEEE ICRA 2024 - Workshop on Bioinspired, Soft, and Other Novel Design Paradigms for Aerial Robotics}}{{Cite journal |last1=Chen |first1=Yufeng |last2=Wang |first2=Hongqiang |last3=Helbling |first3=E. Farrell |last4=Jafferis |first4=Noah T. |last5=Zufferey |first5=Raphael |last6=Ong |first6=Aaron |last7=Ma |first7=Kevin |last8=Gravish |first8=Nicholas |last9=Chirarattananon |first9=Pakpong |last10=Kovac |first10=Mirko |last11=Wood |first11=Robert J. |date=2017-10-25 |title=A biologically inspired, flapping-wing, hybrid aerial-aquatic microrobot |url=https://www.science.org/doi/10.1126/scirobotics.aao5619 |journal=Science Robotics |language=en |volume=2 |issue=11 |doi=10.1126/scirobotics.aao5619 |pmid=33157886 |issn=2470-9476}} which, regarding flight dynamics, emulate bees and fruit flies, respectively. Harvard University invented the RoboBee, a miniature robot that mimics a bee fly, takes off and lands like one, and moves around confined spaces. It can be used in self-driving pollination and search operations for missing people and things. The DelFly Nimble, developed by the Delft University of Technology, is one of the most agile micro aerial vehicles that can mimic the maneuverability of a fruit fly by doing different tricks due to its minimal weight and advanced control mechanisms.

Due to their small size, microbots are potentially very cheap, and could be used in large numbers (swarm robotics) to explore environments which are too small or too dangerous for people or larger robots. It is expected that microbots will be useful in applications such as looking for survivors in collapsed buildings after an earthquake or crawling through the digestive tract. What microbots lack in brawn or computational power, they can make up for by using large numbers, as in swarms of microbots. Bioinspired microrobots have emerged as a game-changing tool in the quest for precise drug delivery.{{Cite journal |last=Ghosh |first=Shampa |last2=Bhaskar |first2=Rakesh |last3=Mishra |first3=Richa |last4=Arockia Babu |first4=M. |last5=Abomughaid |first5=Mosleh Mohammad |last6=Jha |first6=Niraj Kumar |last7=Sinha |first7=Jitendra Kumar |date=September 2024 |title=Neurological insights into brain-targeted cancer therapy and bioinspired microrobots |url=https://pubmed.ncbi.nlm.nih.gov/39029869/ |journal=Drug Discovery Today |volume=29 |issue=9 |pages=104105 |doi=10.1016/j.drudis.2024.104105 |issn=1878-5832 |pmid=39029869}} These microscopic robots are designed to navigate the human body with a degree of precision previously unimaginable.

Potential applications with demonstrated prototypes include:

{{Excerpt|Biohybrid microswimmer|Biomedical applications|paragraphs=1}}

For example, there are biocompatible microalgae-based microrobots for active drug-delivery in the brain, lungs and the gastrointestinal tract,{{cite news |title=Algae micromotors join the ranks for targeted drug delivery |url=https://cen.acs.org/biological-chemistry/biotechnology/Algae-micromotors-join-ranks-targeted/100/web/2022/10 |access-date=19 October 2022 |work=Chemical & Engineering News |language=en}}{{cite journal |last1=Zhang |first1=Fangyu |last2=Zhuang |first2=Jia |last3=Li |first3=Zhengxing |last4=Gong |first4=Hua |last5=de Ávila |first5=Berta Esteban-Fernández |last6=Duan |first6=Yaou |last7=Zhang |first7=Qiangzhe |last8=Zhou |first8=Jiarong |last9=Yin |first9=Lu |last10=Karshalev |first10=Emil |last11=Gao |first11=Weiwei |last12=Nizet |first12=Victor |last13=Fang |first13=Ronnie H. |last14=Zhang |first14=Liangfang |last15=Wang |first15=Joseph |title=Nanoparticle-modified microrobots for in vivo antibiotic delivery to treat acute bacterial pneumonia |journal=Nature Materials |date=22 September 2022 |volume=21 |issue=11 |pages=1324–1332 |doi=10.1038/s41563-022-01360-9 |pmid=36138145 |pmc=9633541 |bibcode=2022NatMa..21.1324Z |language=en |issn=1476-4660}}{{cite journal |last1=Zhang |first1=Fangyu |last2=Li |first2=Zhengxing |last3=Duan |first3=Yaou |last4=Abbas |first4=Amal |last5=Mundaca-Uribe |first5=Rodolfo |last6=Yin |first6=Lu |last7=Luan |first7=Hao |last8=Gao |first8=Weiwei |last9=Fang |first9=Ronnie H. |last10=Zhang |first10=Liangfang |last11=Wang |first11=Joseph |title=Gastrointestinal tract drug delivery using algae motors embedded in a degradable capsule |journal=Science Robotics |date=28 September 2022 |volume=7 |issue=70 |pages=eabo4160 |doi=10.1126/scirobotics.abo4160 |pmid=36170380 |pmc=9884493 |s2cid=252598190 |language=en |issn=2470-9476}} and magnetically guided engineered bacterial microbots for 'precision targeting'{{cite journal |last1=Schmidt |first1=Christine K. |last2=Medina-Sánchez |first2=Mariana |last3=Edmondson |first3=Richard J. |last4=Schmidt |first4=Oliver G. |title=Engineering microrobots for targeted cancer therapies from a medical perspective |journal=Nature Communications |date=5 November 2020 |volume=11 |issue=1 |pages=5618 |doi=10.1038/s41467-020-19322-7 |pmid=33154372 |pmc=7645678 |bibcode=2020NatCo..11.5618S |language=en |issn=2041-1723|doi-access=free}} for fighting cancer{{cite news |last1=Thompson |first1=Joanna |title=These tiny magnetic robots can infiltrate tumors — and maybe destroy cancer |url=https://www.inverse.com/innovation/bacteria-robotic-cancer-treatment |access-date=21 November 2022 |work=Inverse |language=en}}{{cite journal |last1=Gwisai |first1=T. |last2=Mirkhani |first2=N. |last3=Christiansen |first3=M. G. |last4=Nguyen |first4=T. T. |last5=Ling |first5=V. |last6=Schuerle |first6=S. |title=Magnetic torque–driven living microrobots for increased tumor infiltration |journal=Science Robotics |date=26 October 2022 |volume=7 |issue=71 |pages=eabo0665 |doi=10.1126/scirobotics.abo0665 |pmid=36288270 |language=en |issn=2470-9476|biorxiv=10.1101/2022.01.03.473989|s2cid=253160428 }} that all have been tested with mice.

• Artificial intelligence
• Claytronics
• Microswimmer
• Biohybrid microswimmer
• Nanobiotechnology#Nanomedicine

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