8:30 AM - CP07.05.01
Controllable Elastomer Shape Modulation with Solvent Droplet Sequence
Akshay Phadnis1,Konrad Rykaczewski1
Arizona State University1
Stimuli sensitive polymers that swell in response to interaction with various solvents offer possibilities to achieve controllable shape transformations. Temporal interaction of these materials with solvent, when controlled locally, can be translated into programmable shape modulation.1–3These geometrical transformations occur over a time scale that depends upon the solvent and the material properties, as well as the size/shape of the material and thus can be easily controlled.4Here, we use coupled experimental and theoretical methods to quantify geometry dependent shape transformations of rubbery materials that are locally subjected to a train of solvent droplets. Based on relative comparison between diffusion time scale and droplet pulse period, we identify regimes where such shape transformations can be achieved and controlled. This regime is achieved when the two timescales are comparable whereas equilibrium swelling occurs at the two extremes of this scaling. To demonstrate the various regimes, we study swelling of six cylindrical geometries of PDMS with varying aspect ratio subjected to pulsating drops of n-hexane. As a result, a localized swelling feature incremental in time and space domain is observed. Furthermore, we show that the characteristic of this swelling feature depends strongly on the sample aspect ratio relative to the droplet size. We demonstrate this using two cases of cylindrical geometries and a custom finite element model. We use this validated model to predict the geometries of rest of the cases and show dependence of characteristic swelling feature on sample aspect ratio. These deformations are magnified during the droplet-train impact but dissipate during post-train polymer equilibration. Our results also show that while swelling shape is a function of lateral dimensions of the sample, with the extent of swelling increases with the elastomer sample thickness.5
1. Holmes, D. P. et al.Bending and twisting of soft materials by non-homogenous swelling. Soft Matter7,5188 (2011).
2. Stoychev, G., Zakharchenko, S., Turcaud, S., Dunlop, J. W. C. & Ionov, L. Shape-programmed folding of stimuli-responsive polymer bilayers. ACS Nano6,3925–3934 (2012).
3. Lee, H., Zhang, J., Jiang, H. & Fang, N. X. Prescribed pattern transformation in swelling gel tubes by elastic instability. Phys. Rev. Lett.108,1–5 (2012).
4. Holmes, D. P. & Crosby, A. J. Snapping surfaces. Adv. Mater.19,3589–3593 (2007).
5. Phadnis, A., Manning, K. C., Sanders, I., Burgin, T. P. & Rykaczewski, K. Droplet-train induced spatiotemporal swelling regimes in elastomers. Soft Matter14,5869–5877 (2018).