Gunduz, O; (2013) Novel Microfluidic Device Generation of Bubbles, Particles and Capsules for Biomedical Engineering Applications. Doctoral thesis , UCL (University College London).

Abstract

Bubble Science is a rapidly growing field, which has applications in (but not restricted to) health, climate and food engineering. Within these remits, one area of interest is related to the surface of bubbles. In this thesis specially designed and constructed microfluidic devices are combined with polymeric solutions to generate near uniform bubbles with smart coatings. Conventional bubbles possess coatings, which burst or collapse resulting in daughter bubbles or debris. The coatings developed in this study demonstrate particle precipitation from the bubbles surface. In this sense the structure is downscaling in size by a new mechanism proposed for bubble breakdown. In addition to this method, the size of resulting particles can be controlled. The in-situ particle-forming step also provides a pathway, which can retain bio- and chemical media during the formation process. Although several fields can benefit from such platforms, one such area is drug delivery, where this method is a novel approach in particle forming and delivery, when compared to conventional encapsulation routes. After initially demonstrating the process using a T-junction device was used to produce drug loaded particles with haematoxylin dye and estradiol drug using a novel bubble encapsulation system, a simple microfluidic V-junction device was used to prepare near-monodisperse polymer coated microbubbles using a hydrophobic polymer (ethylcellulose). From this coating, nanoparticles were produced continuously at a rate of ~5×106 per minute. It has been shown that these particles can be used as nanocarriers for a hydrophilic drug such an amoxicillin. During processing, varying the gas pressure has a significant effect on the nanocarrier diameter, thus we are able to control the diameter of nanocarriers (between 40 and 800 nm). Encapsulation efficiency using this process was in the range 65–88%, increasing with decreasing particle diameter and the drug-loading (Amoxicillin) was ~0.6mg. An X-junction microfluidic device was also used to prepare N2 bubbles using Tween. This method delivered a new route to generate significantly smaller bubbles (<5 m in diameter) with narrow size distribution. Moreover, Janus (two-phase) submicrometre size particles (710 nm) can also be generated using this X-junction device. The results from these devices and polymer coatings demonstrate potential applications as nanocarriers, which have greater control on size, shape and distribution. These factors are crucial for advancing healthcare science.

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