(572f) Temperature-Directed in Situ Steering of Shape-Morphing Particles | AIChE

(572f) Temperature-Directed in Situ Steering of Shape-Morphing Particles

Authors 

Lee, J. G. - Presenter, Louisiana State University
Duarte, A. R., University of Colorado Boulder
Shields, C. W. IV, University of Colorado, Boulder
Jeon, S. J., Kumoh National Institute of Technology
Hayward, R., University of Colorado Boulder
In nature, microorganisms undergo directed shape transformations to propel through viscous fluids. For example, bacteria actively rearrange their flagella to swim towards remote sources of nutrients. Active particles are synthetic analogues of these natural swimmers because they can efficiently propel through viscous liquids. However, most active particles developed to date lack the ability to undergo the shape transformations observed in microorganisms due to limitations in manufacturing stimuli-responsive materials at the microscale. Here, we present the shape-dependent propulsion of stimuli-responsive microparticles with reprogrammable bending. These shape-morphing particles are fabricated from a bilayer of a thermoresponsive hydrogel and a non-swelling glassy polymer (poly(p-methyl styrene-co-acrylamidobenzophenone), PpMS). These photocurable layers are lithographically patterned into rectangular plates (40 µm by 4 µm; 4 µm thick). Due to the large change in swelling of the hydrogel induced by temperature changes around the volume phase transition, the microparticles exhibit dramatic changes in curvature, morphing from nearly flat plates at 60°C to C-shaped particles at 10°C. When powered by AC electric fields, the particles change their swimming trajectory as they change shape due to the unbalanced hydrodynamic flows around their surfaces. The observed motions of the particles include stop-and-go and directional inversion upon changing the fluid temperature and electric field frequency. The principles used in this study lay a foundation to design new types of microrobots that can transverse complex environments by changing their direction of propulsion on demand.