Microswimmers

We are interested in the development and operation of robotic devices at very small scales, including structures that can swim. We have built several microswimmers that are capable of propulsion using only body-shape changes. Using molecular switches and dyes and structured light permits us to reversibly deform a body made from a liquid crystal elastomer so that it swims. Similarly, we have used soft materials to realize the first reciprocal swimmer, which can overcome the scallop theorem. Our research effort in this area aims to develop new mechanisms that can be used to build and operate microrobots. We address fundamental questions and explore applications in minimally invasive medicine.

Realizing devices that possess robotic functionalities at these small scales is challenging, as no sensors, actuators, controllers, or even mechanisms exist that can be used to build microswimmers and robots. Most artificial microrobots so far consist of monolithic structures that are moved by external fields. This calls for radically new solutions. Molecular materials can be used to endow microrobots with robotic functionalities. For example, elastomers and other flexible materials can obviate the need for joints and mechanisms. This approach has allowed us to develop microrobots that can deform under the action of external magnetic fields, and consequently propel and swim in different environments – from simple liquids to non-Newtonian fluids similar to bodily liquids. We also work in chemical swimmers (active mattor, chemical motors) and the question what is the smallest swimmer that can be realized. The latter involves research on enzymes, DNA, and molecular structures.

“Light- and magnetically actuated FePt microswimmers”, V. Kadiri, J. Günther, S. Kottapalli, R. Goyal, F. Peter, M. Alarcon-Correa, K. Son, H. Barad, P. Fischer, Eur. Phys. J. E44, 74 (2021).

“Light‐Controlled Micromotors and Soft Microrobots”, S. Palagi, D.P. Singh, P. Fischer, Adv. Opt. Mat.7: 1900370, (2019).

“Role of symmetry in driven propulsion at low Reynolds number”, J. Sachs, K.I. Morozov, O. Kenneth, T. Qiu, N. Segreto, P. Fischer, A.M. Leshansky, Phys. Rev. E98, 063105, (2018).

"Swimming by Reciprocal Motion at Low Reynolds Number", Tian Qiu, Tung-Chun Lee, Andrew G. Mark, Konstantin I. Morozov, Raphael Münster, Otto Mierka, Stefan Turek, Alexander M. Leshansky, and Peer Fischer, Nature Comm. 5: 5119 (2014).

“Structured light enables biomimetic swimming and versatile locomotion of photo-responsive soft microrobots”, S. Palagi, A. G. Mark, S. Y. Reigh, K. Melde, T. Qiu, H. Zeng, C. Parmeggiani, D. Martella, A. S. Castillo, N. Kapernaum, F. Giesselmann, D. S. Wiersma, E. Lauga, and P. Fischer, Nature Materials 15, 647–653 (2016) doi:10.1038/nmat4569.