| 1. |
- Ghosh, Somnath, et al.
(författare)
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Microfluidic production of snowman-shaped Janus hydrogel particles
- 2019
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757. ; 573, s. 205-210
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Tidskriftsartikel (refereegranskat)abstract
- We present a simple microfluidic-based synthesis protocol to fabricate snowman like Janus hydrogel particles of poly(N-isopropylacrylamide) (PNIPAM) in micron length scale. Particles are synthesized by emulsifying a hydrogel solution (water (w)/oil (o)) followed by partial solvent evaporation. Solvent evaporation allows the hydrogels to concentrate within the droplet and phase separate into a monomer-abundant and a sparse phase. Due to the difference in interfacial tension and chemical properties of the two phases, emulsion droplets are deformed into snowman like Janus droplets. After cross-linking the monomer by UV irradiation, the particles are transferred into water. The resulting Janus colloids exhibit thermo-responsive behavior and form self-assembled structures.
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| 2. |
- Ghosh, Somnath
(författare)
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Three-dimensional microplate formation with evaporating nanoparticle suspensions on superhydrophobic surfaces
- 2017
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757. ; 529, s. 901-906
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Tidskriftsartikel (refereegranskat)abstract
- The concept of evaporation driven self-assembly of nanoparticles is exploited to fabricate three dimensional microstructures on textured superhydrophobic surfaces. The evaporative droplets always remain in Cassie–Baxter state during the process of drying. However, the wetting transition from Cassie to Wenzel state has been observed for pure water drop on similar surfaces. After complete evaporation, residual particles form a (microhyphen) plate like structure. The area of the final structure is smaller than the initial contact area of the drop. Evaporating droplets are visualized from two directions to keep track of the drop radius and apparent contact angle.
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| 3. |
- Peng, Feifei, et al.
(författare)
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A droplet-based microfluidics route to temperature-responsive colloidal molecules
- 2019
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 123:43, s. 9260-9271
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Tidskriftsartikel (refereegranskat)abstract
- Small clusters of spherical colloids that mimic real molecules, so-called colloidal molecules, hold great promise as building blocks in bottom-up routes to new materials. However, their typical hard sphere nature has hampered their assembly into ordered structures, largely due to a lack of control in the interparticle interactions. To provide easy external control of the interactions, the present work focuses on the preparation of colloidal molecules from temperature-responsive microgel particles that undergo a transition from a soft repulsive to a short-range attractive state as their characteristic volume phase transition temperature (VPTT) is crossed. Preparation of the colloidal molecules starts with the use of a droplet-based microfluidics device to form highly uniform water-in-oil (W/O) emulsion droplets containing, on average and with a narrow distribution, four microgels per droplet. Evaporation of the water then leads to the formation of colloidal molecule-like clusters, which can be harvested following cross-linking and phase transfer. We use a mixture of two types of microgels, one based on poly(N-isopropylacrylamide) (PNIPAM) and the other on poly(N-isopropylmethacrylamide) (PNIPMAM), to prepare bicomponent colloidal molecules, and show that the difference in VPTT between the two allows for induction of attractive interparticle interactions between the PNIPAM interaction sites at temperatures in between the two VPTTs, analogous to the interactions among patchy biomacromolecules such as many proteins.
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