Shape-morphing active particles with invertible effective polarizability for conﬁgurable locomotion and steering

Sep 30, 2026

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Shape-morphing active particles that propel in low-Reynolds-number fluids are addressed by introducing stimuli-responsive systems with fully reversible, shape-dependent propulsion. The particles are bilayer rectangular microscale prisms made from a thermoresponsive hydrogel and a non-swelling glassy polymer; temperature shifts near the hydrogel phase transition drive large curvature changes and alter effective polarizability. Under AC electric fields, geometry–polarizability coupling enables programmable linear and helical modes, while sequential temperature programming produces encoded in situ steering and reconﬁgurable locomotion.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages13

Reading Time33 min

AccessFree to download

Introduction

Biological and synthetic active-matter motivation

Gap in rigid active-particle designs

Proposed approach and particle construction

Bilayer stimulus-responsive microscale prisms

Model system and geometric morphing

Driving and control mechanism

AC-field alignment and effective polarizability

Temperature-programmed propulsion and steering

Context within microscale locomotion theory

Article [https://doi.org/10.1038/s41467-025-65482-9](https://doi.org/10.1038/s41467-025-65482-9) Shape-morphing active particles with invertible effective polarizability for conﬁgurable locomotion and steering Received: 12 March 2025 | Accepted: 16 October 2025 | | --- | | | | Check for updates | Jin Gyun Lee1,5, Seog-Jin Jeon 1,2,5, Alanna R. Duarte1, Matthew Ticknor3, Montana B. Minnis1, Ryan C. Hayward 1,3 & C. Wyatt Shields IV 1,3,4 Active particles are analogs of microorganisms in that they locally dissipate energy to propel in low Reynolds number ﬂuids. However, most active particles lack the ability to undergo controlled shape transformations that change how they move in response to environmental cues. Here, we present a class of stimuli-responsive active particles that exhibit fully reversible, shapedependent propulsion. The particles consist of a bilayer ofathermoresponsive hydrogel and a non-swelling glassy polymer, patterned into rectangular microscale prisms. Temperature changes near the phase transition of hydrogel cause large curvature shifts, from ﬂat plates at 35 °C to crescent shapes at 20 °C, accompanied by changes in effective polarizability. When powered by AC electric ﬁelds, this coupling between geometry and polarizability enables programmable propulsion modes including linear and helical motions. Sequential temperature changes allow encoded in situ steering, establishing a design principle for microscale active systems capable of adaptive propulsion and reconﬁguration. Microorganisms adapt their shape in response to their environment, enhancing their proliferation and survival1–4. For instance, Tetrahymena thermophila, a unicellular organism within the ciliated Protozoa group, swims upwards, forming dense swarms near the surface of water where oxygen, food, and light are more abundant. Initially, cultures of Tetrahymena thermophila exposed to infrared light grow normally, but as food becomes scarce, the cells elongate into spindles, swim 50% faster than their normal counterparts, and follow straighter paths toward food sources5. This increased motility is crucial for their formation, growth, and survival. Active particles are synthetic analogs of microorganisms by mimicking some of their dissipative behaviors6–9. Particularly, selfphoretic active particles create local gradients of energy along their surfaces, driving asymmetric ﬂuid ﬂows at the single-particle level10–15. Their mechanism of motion is inherent in their design, as they asymmetrically draw and dispel energy, generating local gradients of force that propel them16–20. Active particles hold enormous promise for applications such as drug delivery21–24, biosensing25,26, and environmental remediation27,28. Despite their usefulness, most active particle systems developed to date are geometrically rigid, unable to change their shape in response to external stimuli due to difﬁculties in fabricating and controlling shape-morphing soft materials at the microscale29. We note one intriguing exception involving clusters of swelling and non-swelling microspheres that undergo electrokinetic propulsion16. Recently, stimuli-responsive polymers that change properties in response to environmental conditions have led to applications as smart materials30–34, including biomedical devices32,35–39, ﬂexible electronics40–43, sensors44–46, and actuators47–50. In this article, we present a class of shape-morphing active particles fabricated by layering a rigid polymer with a thermoresponsive 1Department of Chemical and Biological Engineering, University of Colorado Boulder, Boulder, CO, USA. 2Department of Polymer Science and Engineering, Kumoh National Institute of Technology, Gumi-si, Gyeongbuk, Republic of Korea. 3Materials Science and Engineering Program, University of Colorado Boulder, Boulder, CO, USA. 4Biomedical Engineering Program, University of Colorado Boulder, Boulder, CO, USA. 5These authors contributed equally: Jin Gyun Lee, Seog

FAQs

What problem do the authors address in existing active-particle systems?

Most active particle systems are geometrically rigid, limiting their ability to change shape in response to external stimuli. The work targets the lack of controlled shape transformations that alter motion based on environmental cues.

How do the particles change shape, and what triggers it?

Temperature changes near the hydrogel phase transition cause large curvature shifts, transforming flat plate-like structures into crescent shapes (and related geometries) while simultaneously changing effective polarizability.

How does AC electric-field coupling enable controllable propulsion and steering?

AC electric fields couple particle geometry with effective polarizability, breaking time-reversal symmetry through temperature-dependent microscale fluid flows. Sequential temperature changes then encode in situ steering, enabling programmable linear and helical propulsion modes.

Sep 30, 2026

Upload by Miles