(a) Schematic of the microfluidic flow focusing geometry used for the continuous production of single and multilayer biopolymer microparticles. Insert—corresponding dimensions of flow-focusing section. (b) Schematic showing regions of the microfluidic device: droplet formation, solidification and deposition of a single (coating) layer.
Evolution of storage modulus as a function of time during the redox-initiated cross-linking reaction of F68DA 15 wt. % aqueous solution (triangles) at 40 rad/s and 10% strain and 20wt. % solution (spheres) at 40 rad/s and 15% strain. The induction time of the reaction varies when decreasing the concentration of accelerator (TEMED) in the original reactive solution from 30 ml/g(DA PF-68) (open symbols) to 15 ml/g(DA PF-68) (filled symbols). The concentration of APS is the same for all initial reactive solutions: 4% (w/w(DA PF-68)). There is no effect of the amount of TEMED on the final modulus.
Images showing differences in droplet size as a function of flowrates of continuous and dispersed phases. (a) QC =0.5 ml/h, QD= 2 ml/h, (b) QC = 0.5 ml/h, QD = 6 ml/h, (c) QC = 1 ml/h, QD = 8 ml/h.
(a) SEM image of DA F-127 cross-linked microparticles produced on-chip via a redox-initiated reaction. The particle size is approximately 1 μm. (b) TEM images of the same system. Note the dense core and diffuse shell.
Absorption spectra for (1) V56 in DI water, (2) a glass slide, (3) a quartz slide.
(a) Optical microscopy image of a DA PF-127 capsule flowing in the channel post UV initiation, showing the formation of a shell of different density to the centre of the particle. (b) Optical microscopy images of DA PF-127 photo cross-linked particles deposited on a microscope slide after collection from the device. (c) SEM images of DA PF-68 (1) and DA PF-127 (2) cross-linked microcapsules produced on-chip via a photo-initiated reaction. The particle size is approximately 60 and 80 μm, respectively.
(a) Axisymmetric co-flowing channel configuration for the introduction of a MVP solution into the main channel where DA PF-127 droplets/particles are flowing. The two continuous phases are partially miscible and do not diffuse into each other instantaneously. A DEAP solution in DMC is introduced further downstream. (b) A solution of 2 wt. % PLA-PEO-PLA in DMC is introduced via the first set of co-flowing channels and hexadecane is introduced via the second flow-focusing junction to push down the polymer solution onto the surface of the particles.
SEM images of (a) DA PF-68 cross-linked microcapsules coated with PLA-PEO-PLA, (b) DA PF-127 cross-linked microcapsules coated with PVP, (c) DA PF-127 cross-linked microparticles coated with a 1st layer of PVP and a 2nd layer of PLA-PEO-PLA.
Images obtained with an inverted microscope Olympus IX81 using (a) a phase contrast objective and (b) a green fluorescent filter.
Release data and profiles for vitronectin (grey line), HRP (dotted line) and vitamin B12 (black line), from cross-linked DA PF-127 macro (bulk)-gels. The amount of vitronectin released after 4, 5 and 6 days from DA PF-127 cross-linked microparticles prepared on-chip is reported (triangles) for comparison.
Release profiles for Vitamin B12 encapsulated in cross-linked DA PF-68 macrogels (open symbols, dotted line) and in the case of cross-linked DA PF-68 particles produced within the microfluidic device (solid symbols, full line).
Residence times of the droplets/particles in the channel, as a function of the flow rate of the continuous phase (QC), in Zone 1 and in Zone 2 (see Figure 5 for partition).
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