Scale-reconfigurable miniature ferrofluidic robots for negotiating sharply variable spaces

Abstract

Magnetic miniature soft robots have shown great potential for facilitating biomedical applications by minimizing invasiveness and possible physical damage. However, researchers have mainly focused on fixed-size robots, with their active locomotion accessible only when the cross-sectional dimension of these confined spaces is comparable to that of the robot. Here, we realize the scale-reconfigurable miniature ferrofluidic robots (SMFRs) based on ferrofluid droplets and propose a series of control strategies for reconfiguring SMFR’s scale and deformation to achieve trans-scale motion control by designing a multiscale magnetic miniature robot actuation (M3RA) system. The results showed that SMFRs, varying from centimeters to a few micrometers, leveraged diverse capabilities, such as locomotion in structured environments, deformation to squeeze through gaps, and even reversible scale reconfiguration for navigating sharply variable spaces. A miniature robot system with these capabilities combined is promising to be applied in future wireless medical robots inside confined regions of the human body.

Water-Immiscible Coacervate as a Liquid Magnetic Robot for Intravascular Navigation

“…Magnetic miniature ultrasoft robots that enable noninvasive access to some deep confined anatomical sites inside the human body guided by external magnetic fields are of significant interest in biomedical fields. − However, most of the existing soft robots are based on elastomers and hydrogels with limited deformability and are difficult to squeeze through narrow crevices much smaller (for example, 20 times) than the robot size. − For instance, in blood capillaries even some large-sized nanoparticles risk being trapped and lead to microvascular obstruction and rupture. − To address the above challenges, a few groundbreaking magnetically actuatable liquid droplets, such as ferrofluids, − and liquid metals, − have been proposed with fascinating shape-morphing abilities for in vitro cargo delivery. Despite these advances, the limited operating conditions, such as the required surface wettability and pH value, ,− and the relatively poor biocompatibility of these oil-based or metal-based liquid droplets greatly hamper their in vivo biomedical applications.…”

Chemical Power for Swarms of Microscopic Robots in Blood Vessels

“…If the group is large and compact enough that some robots are completely surrounded by others, the robots at the surface of the group could share collected oxygen with those inside, or the robots could occasionally change positions so each robot spends part of the time at the surface of the group. When vessels become too small for the group, the robots could disperse into smaller groups or individual robots, adjusting the size to match that of the vessels [24].…”

Bio‐Mimic, Fast‐Moving, and Flippable Soft Piezoelectric Robots

“…Soft robots are composed of soft materials with low stiffness and are driven by soft actuators. Several different types of soft actuators have been developed such as light actuators, [1][2][3][4][5][6][7] electrical actuators, [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] thermal actuators, [27][28][29][30][31][32][33][34][35][36] DOI: 10.1002/advs.202300673 magnetic actuators, [37][38][39][40][41][42][43][44][45][46][47] and fluidic actuators. [48][49][50]…”

“…Soft robots are composed of soft materials with low stiffness and are driven by soft actuators. Several different types of soft actuators have been developed such as light actuators, [ 1–7 ] electrical actuators, [ 8–26 ] thermal actuators, [ 27–36 ] magnetic actuators, [ 37–47 ] and fluidic actuators. [ 48–53 ] Soft actuators and body structures enable more degrees of freedom.…”