Rolling of soft microbots with tunable traction

Abstract

Microbot (μbot)–based targeted drug delivery has attracted increasing attention due to its potential for avoiding side effects associated with systemic delivery. To date, most μbots are rigid. When rolling on surfaces, they exhibit substantial slip due to the liquid lubrication layer. Here, we introduce magnetically controlled soft rollers based on Pickering emulsions that, because of their intrinsic deformability, fundamentally change the nature of the lubrication layer and roll like deflated tires. With a large contact area between μbot and wall, soft μbots exhibit tractions higher than their rigid counterparts, results that we support with both theory and simulation. Upon changing the external field, surface particles can be reconfigured, strongly influencing both the translation speed and traction. These μbots can also be destabilized upon pH changes and used to deliver their contents to a desired location, overcoming the limitations of low translation efficiency and drug loading capacity associated with rigid structures.

Asymmetric microfiber actuators with reciprocal deformation

“…These microscopic devices have garnered considerable research attention and exhibit substantial promise across diverse domains such as microlifters, 1 micro-joints, 2 artificial muscles, 3-5 energy harvesting, 6 biomedicine, [7][8][9][10] microvalves, 11 liquid seals, 12 bioinspired transparency, 13,14 color change, 15 and beyond. To power and maneuver these microactuators, a spectrum of energy sources has been harnessed, including light, [16][17][18][19][20] electricity, 19,[21][22][23] acoustics, 24 thermal energy, 18 magnetic fields, [25][26][27] and chemical reactions 28,29 (Table S1, ESI †). The choice of materials for microactuators spans composites, 26,30,31 carbon nanotubes, 22,30 liquid crystal elastomers, 5,32-34 and biodegradable 35,36 and hygroscopic 36 polymers 20 and more.…”

Untethered Small-Scale Machines for Microrobotic Manipulation: From Individual and Multiple to Collective Machines

“…The advances in developing USSMs with high manipulation precision and multiple degrees-of-freedom (DoFs) of motion have been recently demonstrated thanks to the development of manipulation mechanisms and the in-depth understanding of fundamental science. Here the USSMs are defined as mobile miniature devices in dimensions from micro/nanometers to millimeter-scale that can perform tasks under wireless control. − This definition is from the view of the microrobotic manipulation system since a moving structure or particle itself cannot be defined as a machine. The mechanically connected manipulators are replaced with USSMs that can be wirelessly actuated by several types of external powers (e.g., magnetic, acoustic, electric fields, and light), − self-generated propulsion, − and hybrid power. , The progress in the untethered system-based microrobotic manipulation has benefited from the distinctive ability of USSMs, such as wireless feedback control and on-demand actuation in complex environments. − …”

Magnetically locked Janus particle clusters with orientation-dependent motion in AC electric fields

“…Micromotors composed of active colloidal particles have found use in a multitude of applications, including drug delivery, 1–4 cell manipulation, 5–7 flexible electronics, 8–10 and cargo transport. 11–15 Such micromotors can be propelled by various energy sources, including magnetic, 16–21 acoustic, 2,22–24 and electric fields, 11,25–28 as well as catalytic reactions.…”