Project description:Methods to make microcapsules - used in a broad range of healthcare and energy applications - currently suffer from poor size control, limiting the establishment of size/property relationships. Here, we use microfluidics to produce monodisperse polyurea microcapsules (PUMC) with a limonene core. Using varied flow rates and a commercial glass chip, we produce capsules with mean diameters of 27, 30, 32, 34, and 35 µm, achieving narrow capsule size distributions of ±2 µm for each size. We describe an automated method of sizing droplets as they are produced using video recording and custom Python code. The sustainable generation of such size-controlled PUMCs, potential replacements for commercial encapsulated systems, will allow new insights into the effect of particle size on performance.
Project description:This paper reports the development of a scalable continuous microfluidic-based method for the preparation of multilayered biopolymer microcapsules and microparticles, with a size range of 1 to 100 μm, in a single-layered polydimethylsiloxane-based device. This new approach has been utilised to produce polyethylene oxide (PEO)-based microparticles, layered with subsequent stage wise coatings of polylactide-based block copolymers and polyvinylpyrrolidone. The production process was shown to allow for on-chip encapsulation of protein and vitamin molecules in the biopolymer micro particles, without any further handling after collection from the device. We have studied the release profiles in the case of model molecules of distinctive molecular weights, namely, vitronectin, horse radish peroxidase, and vitamin B(12). We compared the release properties of the microparticles to those from macro-gels of the same materials prepared off-chip. The results indicated that the microparticles have definitively different molecular weight cut-off characteristics, likely due to a denser microstructure within the microparticles compared to the bulk hydrogels. This difference suggests that significant benefits may exist in the use of this method to produce layered biopolymer microparticles in achieving improved controlled release and encapsulation.
Project description:Microfluidic manufacturing platforms have advanced the production of monodisperse, shape-controlled, and chemically defined micromaterials. However, conventional microfabrication platforms are typically designed and fabricated as single-purpose and single-use tools, which limits their efficiency, versatility, and overall potential. We here present an on-the-fly exchangeable nozzle concept that operates in a transparent, 3D, and reusable microfluidic device produced without cleanroom technology. The facile exchange and repositioning of the nozzles readily enables the production of monodisperse water-in-oil and oil-in-water emulsions, solid and core-shell microspheres, microfibers, and even Janus type micromaterials with controlled diameters ranging from 10 to 1000 μm using a single microfluidic device.
Project description:Organic phase-change materials (PCMs) hold promise in developing advanced thermoregulation and responsive energy systems owing to their high latent heat capacity and thermal reliability. However, organic PCMs are prone to leakages in the liquid state and, thus, are hardly applicable in their pristine form. Herein, we encapsulated organic PCM n-Octadecane into polyurethane capsules via polymerization of commercially available polymethylene polyphenylene isocyanate and polyethylene glycol at the interface oil-in-water emulsion and studied how various n-Octadecane feeding affected the shell formation, capsule structure, and latent heat storage properties. The successful shell polymerization and encapsulation of n-Octadecane dissolved in the oil core was verified by confocal microscopy and Fourier-transform infrared spectroscopy. The mean capsule size varied from 9.4 to 16.7 µm while the shell was found to reduce in thickness from 460 to 220 nm as the n-Octadecane feeding increased. Conversely, the latent heat storage capacity increased from 50 to 132 J/g corresponding to the growth in actual n-Octadecane content from 25% to 67% as revealed by differential scanning calorimetry. The actual n-Octadecane content increased non-linearly along with the n-Octadecane feeding and reached a plateau at 66-67% corresponded to 3.44-3.69 core-to-monomer ratio. Finally, the capsules with the reasonable combination of structural and thermal properties were evaluated as a thermoregulating additive to a commercially available paint.
Project description:Functionalized monodisperse microbubbles have the potential to boost the sensitivity and efficacy of molecular ultrasound imaging and targeted drug delivery using bubbles and ultrasound. Monodisperse bubbles can be produced in a microfluidic flow focusing device. However, their functionalization and sequential use require removal of the excess lipids from the bubble suspension to minimize the use of expensive ligands and to avoid competitive binding and blocking of the receptor molecules. To date, excess lipid removal is performed by centrifugation, which is labor intensive and challenging to automate. More importantly, as we show, the increased hydrostatic pressure during centrifugation can reduce bubble monodispersity. Here, we introduce a novel automated microfluidic 'washing' method. First, bubbles are injected in a microfluidic chamber 1 mm in height where they are left to float against the top wall. Second, lipid-free medium is pumped through the chamber to remove excess lipids while the bubbles remain located at the top wall. Third, the washed bubbles are resuspended and removed from the device into a collection vial. We demonstrate that the present method can (i) reduce the excess lipid concentration by 4 orders of magnitude, (ii) be fully automated, and (iii) be performed in minutes while the size distribution, functionality, and acoustic response of the bubbles remain unaffected. Thus, the presented method is a gateway to the fully automated production of functionalized monodisperse microbubbles.
Project description:Pulsatile delivery of proteins, in which release occurs over a short time after a period of little or no release, is desirable for many applications. This paper investigates the effect of biodegradable polymer shell thickness on pulsatile protein release from biodegradable polymer microcapsules.Using precision particle fabrication (PPF) technology, monodisperse microcapsules were fabricated encapsulating bovine serum albumin (BSA) in a liquid core surrounded by a drug-free poly(lactide-co-glycolide) (PLG) shell of uniform, controlled thickness from 14 to 19 ?m.When using high molecular weight PLG (Mw 88 kDa), microparticles exhibited the desired core-shell structure with high BSA loading and encapsulation efficiency (55-65%). These particles exhibited very slow release of BSA for several weeks followed by rapid release of 80-90% of the encapsulated BSA within 7 days. Importantly, with increasing shell thickness the starting time of the pulsatile release could be controlled from 25 to 35 days.Biodegradable polymer microcapsules with precisely controlled shell thickness provide pulsatile release with enhanced control of release profiles.
Project description:Microbubbles have various applications including their use as carrier agents for localized delivery of genes and drugs and in medical diagnostic imagery. Various techniques are used for the production of monodisperse microbubbles including the Gyratory, the coaxial electro-hydrodynamic atomization (CEHDA), the sonication methods, and the use of microfluidic devices. Some of these techniques require safety procedures during the application of intense electric fields (e.g., CEHDA) or soft lithography equipment for the production of microfluidic devices. This study presents a hybrid manufacturing process using micropipettes and 3D printing for the construction of a T-Junction microfluidic device resulting in simple and low cost generation of monodisperse microbubbles. In this work, microbubbles with an average size of 16.6 to 57.7 μm and a polydispersity index (PDI) between 0.47% and 1.06% were generated. When the device is used at higher bubble production rate, the average diameter was 42.8 μm with increased PDI of 3.13%. In addition, a second-order polynomial characteristic curve useful to estimate micropipette internal diameter necessary to generate a desired microbubble size is presented and a linear relationship between the ratio of gaseous and liquid phases flows and the ratio of microbubble and micropipette diameters (i.e., Qg/Ql and Db/Dp) was found.
Project description:Coacervates have been widely studied as model compartments in protocell research. Complex coacervates composed of disordered proteins and RNA have also been shown to play an important role in cellular processes. Herein, we report on a microfluidic strategy for constructing monodisperse coacervate droplets encapsulated within uniform unilamellar liposomes. These structures represent a bottom-up approach to hierarchically structured protocells, as demonstrated by storage and release of DNA from the encapsulated coacervates as well as localized transcription.
Project description:Mimicking subcellular compartments containing enzymes in organisms is considered a promising approach to substitute for missing or lost cellular functions. Inspired by the multicompartment structures of cellular architectures, we present a novel multienzyme system based on hollow hydrogel microcapsules with flexible enzymatic inverse opal particles. Benefiting from the precise operation capability of the microfluidic electrospray and the remarkable structural color marks in the inverse opal particles, we developed a multienzyme system with controllable number, type, and spatial arrangement of the encapsulated enzymes. The hydrogel shells also could improve enzyme stability against proteolysis in the system. The multienzyme system containing alcohol oxidase and catalase could act as a cascade biocatalyst and reduce alcohol levels in media, providing an alternative antidote and prophylactic for alcohol intoxication. These features indicated that our strategy provides an ideal enzyme cascade reaction system for complex biocatalysis and biomimetic functions of some organelles or organs.