Source-linked AI summary
Adaptive locomotion of artificial microswimmers
Henwei Huang, Fazil Emre Uslu, Panayiota Katsamba, Qianwen Chao, Eric Lauga, Mahmut Selman Sakar, Bradley J. Nelson
TL;DR
Artificial microswimmers generally cannot sense or respond to changing physical conditions. This paper couples programmable magnetic hydrogel structures with fluid properties to produce self-regulated shape and locomotion changes, enabling adaptive movement without onboard sensors.
Problem
Artificial microswimmers lack the environmental sensing and responsiveness of living cells, limiting navigation through changing physical conditions.
Method
The study engineers magnetic hydrogel nanocomposite microswimmers with programmable shapes, magnetization profiles, and locomotion gaits responsive to fluid conditions.
Results
Microswimmers adapt their morphology and locomotion across viscosities, shear flows, and osmotic conditions, including transformations between planar-tailed tubular and helical configurations.
Takeaways & Limitations
Coupling structural and magnetic design with fluid properties enables untethered microswimmers to regulate mobility without onboard sensors.
Takeaways & Limitations
Navigation by squeezing through constrictions can obstruct channels depending on machine surface roughness and chemistry and the channel.
Abstract
from arXiv · showhide
Bacteria can exploit mechanics to display remarkable plasticity in response to locally changing physical and chemical conditions. Compliant structures play a striking role in their taxis behavior, specifically for navigation inside complex and structured environments. Bioinspired mechanisms with rationally designed architectures capable of large, nonlinear deformation present opportunities for introducing autonomy into engineered small-scale devices. This work analyzes the effect of hydrodynamic forces and rheology of local surroundings on swimming at low Reynolds number, identifies the challenges and benefits of utilizing elastohydrodynamic coupling in locomotion, and further develops a suite of machinery for building untethered microrobots with self-regulated mobility. We demonstrate that coupling the structural and magnetic properties of artificial microswimmers with the dynamic properties of the fluid leads to adaptive locomotion in the absence of on-board sensors.
Introduction
The paper develops artificial microswimmers that use fluid–structure coupling, magnetic design, and responsive materials to adapt their morphology, locomotion, and maneuverability without onboard sensors. It examines how viscosity, flow, and osmolarity shape performance across microorganism-inspired architectures.
- Motivation: Artificial microswimmers could enable targeted therapies by crossing biological barriers, moving through bodily fluids, and reaching remote pathological sites.Existing magnetically controlled designs mimic prokaryotic or eukaryotic flagella but differ from living cells in important capabilities.
- Motivation: Electronic circuitry would greatly increase manufacturing complexity and machine size, motivating artificial-material approaches to autonomous microswimmers.Biological actuators and sensors are another proposed route, but the paper focuses on artificial materials.
- Design strategy: Fluid–structure coupling in compliant hydrogel machinery can regulate morphology and function autonomously, while origami principles enable programmable 3D flexible microstructures.Microscale self-folding films can be produced by layering materials with different swelling properties or by patterning structures.
- Microorganism-inspired designs: The study compares microswimmers inspired by Caulobacter crescentus, Helicobacter pylori, and Borrelia burgdorferi, using magnetic moments perpendicular to their long axes to mimic flagellar propulsion.Shape anisotropy and magnetization profiles are varied to examine their effects on swimming and maneuverability.
- Viscosity-dependent locomotion: At 3 mPa∙s, flagellated swimmers with tubular bodies and flexible planar tails moved fastest because oar-like propulsion enhanced body precession.Increasing viscosity reduced motility for all swimmers, with a particularly drastic decline for planar-tailed flagellated swimmers as viscous forces attenuated helical motion.
- Adaptive shape transformation: Elastohydrodynamic deformation enables helical swimmers to pass narrow constrictions and motivates reconfigurable swimmers that transform between planar-tailed tubular and helical morphologies as viscosity rises.At flow rates higher than 5 ml/min, all tested machines passed through constrictions smaller than their diameter by compression; osmolarity-triggered transformation reduced body size and increased step-out frequency.
Conclusion
The work uses magnetic hydrogel nanocomposites to engineer microswimmers with programmable shapes, magnetization profiles, and locomotion gaits. Swimming-performance analysis across viscosities guides the design of one machine with multiple stable, viscosity-specific configurations.
- Conclusion: Magnetic hydrogel nanocomposites enable microswimmers inspired by microorganisms’ form, locomotion, and plasticity.The materials are used as programmable matter for engineering the microswimmers.
- Conclusion: The same device supports dynamic modulation of shapes, magnetization profiles, and locomotion gaits.This multifunctionality is presented as a capability of the engineered microswimmers.
- Conclusion: Swimming-performance analysis at different viscosities guides a single machine’s multiple stable configurations, each optimized for a different locomotion condition.The conclusion links viscosity-dependent performance analysis to the design of distinct stable configurations.