Three-dimensional axisymmetric flow-focusing device using stereolithography

Abstract

This paper describes a three-dimensional microfluidic axisymmetric flow-focusing device (AFFD) fabricated using stereolithography. Using this method, we can fabricate AFFDs rapidly and automatically without cumbersome alignment needed in conventional methods. The AFFDs are able to be fabricated reproducibly with a micro-sized orifice of diameter around 250 mum. Using this device, we are able to produce monodisperse water-in-oil (W/O) droplets with a coefficient of variation (CV) of less than 4.5%, W/O droplets with encapsulated microbes (CV < 4.9%) and oil-in-water (O/W) droplets (CV < 3.2%) without any surface modifications. The diameter of these droplets range from 54 to 244 mum with respect to the flow rate ratio of the fluids used; these results are in good agreement with theoretical behavior. For applications of the AFFD, we demonstrate that these devices can be used to produce double emulsions and monodisperse hydrogel beads.

Production of uniform droplets using membrane, microchannel and microfluidic emulsification devices

“…To enclose the channels, the PDMS mould is sealed to a flat surface of a glass slide or PDMS block either covalently by plasma oxydation or noncovalently by applying pressure. Cylindrical channels in PDMS can be fabricated by stereolithography (Morimoto et al, 2009), aligning and adhering two semi-circular PDMS channels face-to-face (Wilson et al, 2011), embedding a microfiber in PDMS mould before curing (Takeuchi et al, 2005) or introducing pressured air stream inside rectangular PDMS channels filled with liquid PDMS (Abdelgawad et al, 2011). PDMS is inherently hydrophobic, but can be rendered hydrophilic by oxidation of the PDMS surface (Hillborg et al, 2004), coating with inorganic materials such as silica and titania via sol-gel chemistry (Abate et al, 2008), through layer-by-layer deposition of polyelectrolytes (Bauer et al, 2010), ultraviolet graft polymerization of acrylic acid (Li et al, 2007), etc.…”

“…However, these AFFDs are non-reproducible as they are handmade, and thus unsuitable for mass production. Recently, monolithic acrylic AFFDs have been fabricated by stereolithography (Morimoto et al, 2009), which is a rapid and automatic process for building three-dimensional microstructures highly accurately (Zissi et al, 1996).…”

Microsphere formation using SIFEL microfluidic devices with organic-solvent resistance

“…In dripping, interfacial forces dominate over inertial forces, thus forming droplet close to a junction where two fluid meets. It has been known that we can produce monodisperse droplets under dripping condition (Morimoto et al, 2009). Thus, we aimed to form droplets under dripping condition.…”

Basic Technologies for Droplet Microfluidics

“…Other methods for generating droplets are also available, for instance, using capillary systems [27], axisymmetric "flow-focusing" structured devices [28,29]. In these devices the disperse phase is shielded by the continuous phase from touching the channel wall, and the surface problems could be alleviated.…”