2 research outputs found
Cellulose Nanocrystal Microcapsules as Tunable Cages for Nano- and Microparticles
We demonstrate the fabrication of highly open spherical cages with large through pores using high aspect ratio cellulose nanocrystals with “haystack” shell morphology. In contrast to traditional ultrathin shell polymer microcapsules with random porous morphology and pore sizes below 10 nm with limited molecular permeability of individual macromolecules, the resilient cage-like microcapsules show a remarkable open network morphology that facilitates across-shell transport of large solid particles with a diameter from 30 to 100 nm. Moreover, the transport properties of solid nanoparticles through these shells can be pH-triggered without disassembly of these shells. Such behavior allows for the controlled loading and unloading of solid nanoparticles with much larger dimensions than molecular objects reported for conventional polymeric microcapsules
Bimorph Silk Microsheets with Programmable Actuating Behavior: Experimental Analysis and Computer Simulations
Microscaled self-rolling
construct sheets from silk protein material have been fabricated,
containing a silk bimorph composed of silk ionomers as an active layer
and cross-linked silk β-sheet as the passive layer. The programmable
morphology was experimentally explored along with a computational
simulation to understand the mechanism of shape reconfiguration. The
neutron reflectivity shows that the active silk ionomers layer undergoes
remarkable swelling (eight times increase in thickness) after deprotonation
while the passive silk β-sheet retains constant volume under
the same conditions and supports the bimorph construct. This selective
swelling within the silk-on-silk bimorph microsheets generates strong
interfacial stress between
layers and out-of-plane forces, which trigger autonomous self-rolling
into various 3D constructs such as cylindrical and helical tubules.
The experimental observations and computational modeling confirmed
the role of interfacial stresses and allow programming the morphology
of the 3D constructs with particular design. We demonstrated that
the biaxial stress distribution over the 2D planar films depends upon
the lateral dimensions, thickness and the aspect ratio of the microsheets.
The results allow the fine-tuning of autonomous shape transformations
for the further design of complex micro-origami constructs and the
silk based rolling/unrolling structures provide a promising platform
for polymer-based biomimetic devices for implant applications