During my PhD, I worked on synthesizing thermally responsive photopolymer hydrogels, and patterning spatial crosslinking density for fabricating unique geometries at sub-milimeter scale. During my PhD, I progressed this field from utilizing halftone patterning to a full greyscale patterning using a DLP based projection lithography system. Greyscale lithography enables programming an intended crosslinking/ swelling profile on hydrogel with high accuracy.
This work was part of a large NSF/ AFRL program that aspired to apply principles from origami to get unique mechanical response.
- PhD Thesis: Non-Euclidean Shells: A Study of Growth-Induced Fabrication and Mechanical Multi-Stability
- All academic works: Google Scholar
Greyscale lithography for stimuli responsive gels
- Grayscale gel lithography for programmed buckling of non-Euclidean hydrogel plates
- Journal: Soft Matter
- Authors: Jun-Hee Na, Nakul P Bende, Jinhye Bae, Christian D Santangelo, Ryan C Hayward
- Abstract:
Shape programmable materials capable of morphing from a flat sheet into controlled three dimensional (3D) shapes offer promise in diverse areas including soft robotics, tunable optics, and bio-engineering. We describe a simple method of ‘grayscale gel lithography’ that relies on a digital micromirror array device (DMD) to control the dose of ultraviolet (UV) light, and therefore the extent of swelling of a photocrosslinkable poly(N-isopropyl acrylamide) (PNIPAm) copolymer film, with micrometer-scale spatial resolution. This approach allows for effectively smooth profiles of swelling to be prescribed, enabling the preparation of buckled 3D shapes with programmed Gaussian curvature.
Using surface tension and geometry to self-assemble at air-water interface
- Programmable and reversible assembly of soft capillary multipoles
- Journal: Materials Horizons
- Authors: Jinhye Bae, Nakul P Bende, Arthur A Evans, Jun-Hee Na, Christian D Santangelo, Ryan C Hayward
- Abstract:
- The capillary assembly of stimulus-responsive hydrogel particles with programmed multipolar interactions defined by their prescribed three-dimensional (3D) shapes is demonstrated. Low-energy bending deformations of the particles, driven by surface tension, modifies the interactions between particles, while their temperature-dependent swelling enables switchable assembly.
Kirigami for prescribing shapes
- Nonuniform growth and topological defects in the shaping of elastic sheets
- Journal: Soft Matter
- Authors: Nakul P. Bende, Ryan C. Hayward, Christian D. Santangelo
- Abstract:
We demonstrate that shapes with zero Gaussian curvature, except at singularities, produced by the growth-induced buckling of a thin elastic sheet are the same as those produced by the Volterra construction of topological defects in which edges of an intrinsically flat surface are identified. With this connection, we study the problem of choosing an optimal pattern of growth for a prescribed developable surface, finding a fundamental trade-off between optimal design and the accuracy of the resulting shape which can be quantified by the length along which an edge should be identified.