Agile Underwater Swimming of Magnetic Polymeric Microrobots in Viscous Solutions

Abstract

Miniaturization of polymeric robots leads to difficulties in actuation inside viscous media due to the increased surface drag on the diminutive robot bodies. Herein, agile underwater swimming of polymeric microrobots is presented with the investigation of correlation between the magnetic propulsion and viscous drag on the robot. The polymeric microrobots swim with pivoting and tumbling motions during underwater rotation by in‐plane rotation of two permanent magnets underneath the plane, which results in orbital revolution‐type locomotion with a maximum swimming velocity of 56 body lengths per second (BL s−1). The rotational ability and orbital velocity of the polymeric microrobots are determined by correlated variables, i.e., liquid viscosity and frequency of magnet rotation, as elucidated by experimental results and theoretical analysis. Based on the understanding of underwater orbital maneuvers, the polymeric microrobots achieve agile swimmability at a viscosity similar to that of normal whole blood and self‐correcting maneuverability in diverse vascular‐like environments, including a stenosed tube with a coarse granular hill and a rough‐walled artificial blood vessel. Agile underwater swimming can improve versatile aquatic performances of miniaturized robots in blood vessels with arteriosclerosis or blood clots.

Tunable and responsive photonic bio‐inspired materials and their applications

“…RESPONSIVE MATERIALS -7 of 17 photonics, [74][75][76] soft robotics, [77][78][79][80] switchable surface, [81][82][83] and object guiding. [84,85]…”

“…Photo‐responsive materials not only can transduce photochemical energy to mechanical energy but also change their optical properties. Programmable magneto‐responsive composite materials can be utilized for tuned photonics, [74–76] soft robotics, [77–80] switchable surface, [81–83] and object guiding [84,85] …”

High‐Speed NIR‐Driven Untethered 3D‐Printed Hydrogel Microrobots in High‐Viscosity Liquids

“…[12][13][14][15][16][17][18] External physical stimuli, such as magnetic fields, [19,20] electric fields, [21,22] ultrasound, [23,24] and light, [25,26] can provide remote interventions with regard to the "on/off" states, the velocity and direction of motion, and the position in a controlled manner. [27] Although these designs and propulsion mechanisms have been successful in liquids, their effective propulsion in biological fluids, [28] such as blood, [29] oviduct fluid, [30] and mucus [31] that are complex high-viscosity media, still remains a challenge. [32][33][34][35] Although, in recent years, a few microrobots designs have used helical propellers, [36] asymmetric microrobots, [37] and bionic flagellate microrobots [38,39] to propel in viscosity liquids, there is still Untethered synthetic microrobots have significant potential to revolutionize biomedical interventions therapy in the future.…”

A 5 cm‐Scale Piezoelectric Jetting Agile Underwater Robot

“…[4][5][6] However, additional transmission systems or joints prohibit miniaturization. Currently, smart actuators using functional materials promote the development of miniaturizing robots, [7,8] such as ionic polymer-metal composite actuators (IPMCA), [9][10][11] shape memory alloy actuators (SMAA), [12][13][14] dielectric elastomer actuators (DEA), [15][16][17] piezoelectric actuators (PA), [18][19][20] external stimuli-responsive materials (ES-RM) actuators, [21][22][23][24] pneumatic/hydraulic actuators (P/HA), [25][26][27][28] biohybrid actuators (BA) [29][30][31] and electrothermal actuators (ETA). [32][33][34] The size of the robot can be easily reduced to the centimeter scale as the direct driving mode of the smart actuator.…”