Colloidal Particles that Rapidly Change Shape via Elastic Instabilities

Eric Epstein; Jaewon Yoon; Amit Madhukar; K Jimmy Hsia; Paul V Braun

doi:10.1002/smll.201502198

Colloidal Particles that Rapidly Change Shape via Elastic Instabilities

Small. 2015 Dec 2;11(45):6051-7. doi: 10.1002/smll.201502198. Epub 2015 Oct 9.

Authors

Eric Epstein¹, Jaewon Yoon¹, Amit Madhukar², K Jimmy Hsia², Paul V Braun^{1

2}

Affiliations

¹ Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
² Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.

PMID: 26449185
DOI: 10.1002/smll.201502198

Abstract

The fabrication and properties of pH-responsive colloidal particles are reported, which change shape rapidly (less than 200 ms), nearly independent of the diffusion of the pH altering species that trigger their actuation, and far more rapid than their Brownian motion. These particles are mechanically bistable, as revealed by their hysteretic shape response. Finite element analysis (FEA) shows that mechanical hysteresis and bistability derives from the colloids' spherical curvature. Mechanical characterization of the bilayered polymers comprising the colloidal particles shows that viscoelastic relaxation plays a non-negligible role in limiting the shape switching rate; however, energy landscapes obtained from FEA simulations suggest that by tuning the elastic moduli and thicknesses of the constituent polymer layers, microparticles of the size shown here may be fabricated to actuate on timescales as fast as 1 μs.

Keywords: actuators; colloids; mechanical bistability; stimuli-responsive polymers.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.