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Gao et. al. ACS Appl. Opt. Mater. 2023, 1, 430-434
Wilson-Whitford et. al. Soft Matter, 2023, 19, 47, 9139-9145
Wilson-Whitford et. al. J. Phys. Chem. B., 2024, 128, 26, 6394-6399
Research highlights
Research highlights
Microrollers flow uphill as granular media
Nature Communications 2023, 14, 5829
arxiv | Nat. Commun.
Pour sand into a container and only the grains near the top surface move. The collective motion associated with the translational and rotational energy of the grains in a thin flowing layer is quickly dissipated as friction through multibody interactions. Alternatively, consider what will happen to a bed of particles if one applies a torque to each individual particle. In this paper, we demonstrate an experimental system where torque is applied at the constituent level through a rotating magnetic field in a dense bed of microrollers. The net result is the grains roll uphill, forming a heap with a negative angle of repose. Two different regimes have been identified related to the degree of mobility or fluidisation of the particles in the bulk. Velocimetry of the near surface flowing layer reveals the collective motion of these responsive particles scales in a similar way to flowing bulk granular flows. A simple granular model that includes cohesion accurately predicts the apparent negative coefficient of friction. In contrast to the response of active or responsive particles that mimic thermodynamic principles, this system results in macroscopic collective behavior that has the kinematics of a purely dissipative granular system
Yield stress-enabled microencapsulation of field responsive microparticle suspensions
Soft Matter, 2023, 19, 9139-9145
Try and encapsulate microparticles inside the cores of microcapsules and you will often find that particles adhere to the liquid–liquid interface in a phenomenon known as Pickering stabilization. Particles will remain irreversibly trapped and embedded within the subsequently formed microcapsule membrane. In cases where the encapsulant particles must remain suspended inside the microcapsule core to retain their desired properties or behaviours, Pickering stabilization is detrimental. Here we demonstrate a general procedure using yield stress materials as the core material, where the yield stress of the gel is strong enough to suspend particles against sedimentation, but weak enough to allow spatial manipulation of encapsulant particles using an external field. This external field imparts enough force on particles to disrupt the supporting network and allow particle mobility after encapsulation.
Textured Microcapsules through Crystallization
ACS Appl. Mater. Interfaces 2021, 13(4), 5887-5894
This work demonstrates the fabrication of surface-textured microcapsules formed from emulsion droplets, which are stabilized by an interlocking mesh of needle-like crystals. Crystals of the small-organic-compound decane-1,10-bis(cyclohexyl carbamate) are formed within the geometric confinement of the droplets, through precipitation from a binary-solvent-dispersed phase. This binary mixture consists of a volatile solvent and nonvolatile carrier oil. Crystallization is facilitated upon supersaturation due to evaporation of the volatile solvent. Microcapsule diameter can be easily tuned using microfluidics. This approach also proves to be scalable when using conventional mixers, yielding spikey microcapsules with diameters in the range of 10–50 μm. It is highlighted that the capsule shape can be molded and arrested by jamming using recrystallization in geometric confinement. Moreover, it is shown that these textured microcapsules show a promising enhanced deposition onto a range of fabric fibers.
2025
[10] Sedimenting microrollers navigate saturated porous media, S. R. Wilson-Whitford*^, D. J. Kramer, J. Gao, MC. Roffin and J. F. Gilchrist*, Phys. Rev. E (Under Review) . LINK.
2024
[9] Density matching for microcapsulation of field-responsive suspensions of non-Brownian microparticles, S. R. Wilson-Whitford*^, J. Gao and J. F. Gilchrist, J. Phys. Chem. B., 2024, 128, 6394-6399. Cover. LINK. COVER.
[8] Dynamically controlled emissivity and methods thereof, S. E. Han, J. F. Gilchrist, J. Gao, S. R. Wilson-Whitford and S. M. Han, US. Pat., App. 18/370,954. LINK.
2023
[7] Microrollers flow uphill as granular media, S. R. Wilson-Whitford^, J. Gao, MC. Roffin, W. E. Buckley, and J. F. Gilchrist*, Nat. Commun., 2023, 14, 5829. LINK.
[6] Granular Origami, J. F. Gilchrist* and S. R. Wilson-Whitford, Matter, 2023, 6, 1053-1055. LINK.
[5] Yield stress-enabled microencapsulation of field responsive microparticle suspensions, S. R. Wilson-Whitford*^, MC. Roffin, J. Gao, T. Kaewpetch and J. F. Gilchrist, Soft Matter, 2023, 19, 9139-9145. LINK. COVER.
[4] Dynamic emissivity of self-assembled magnetoresponsive Janus particle chains, J. Gao, S. R. Wilson-Whitford, S. E. Han, S. M. Han and J. F. Gilchrist*, ACS Appl. Opt. Mater., 2023, 1, 430-434. LINK. COVER.
2022
[3] Microcapsule and hair care composition, C. Fidge, S. Golding, S. A. F. Bon, S. R. Wilson-Whitford and J. Merrington, EP4025335A1. LINK.
[2] Microcapsule and hair care composition, C. Fidge, S. Golding, S. A. F. Bon, S. R. Wilson-Whitford and J. Merrington, EP4025334B1. LINK.
2021
[1] Textured microcapsules through crystallization, S. R. Wilson-Whitford^, R. W. Jaggers, B. W. Longbottom, M. K. Donald, G. J. Clarkson and S. A. F. Bon*, ACS Appl. Mater. Interfaces, 2021, 13, 5887-5894. LINK.
^ Lead/co-Lead Author
*: Principal Investigator
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