Highly Tailorable and Monodisperse Porous Beads via Microfluidics

In tissue engineering practice, a scaffold is often needed to deliver cells to the desired body site needing to be repaired. Scaffolds supporting cells can be either implanted through a surgical operation or injected through a laparoscopic device. The latter option is a first-choice in cases where a small and irregularly shaped defect needs to be regenerated. In such circumstances, the cell carrier has to be miniaturised while maintaining the morphological features that make a scaffold an efficient cell culture support, i.e. a uniform and adequate porous texture in terms of pore and interconnect dimensions. In this work, we illustrate a novel and powerful method for the manufacturing of monodisperse porous beads of tailorable dimension (in the range ~ 300÷1500 m) and with an internal porous texture characterised by uniformly sized and fully interconnected pores. The fabrication method relies on the use of a flow-focusing microfluidic chip that generates a monodisperse oil-in-water emulsion (panel b). The aqueous phase of the emulsion contains a biopolymer and an appropriate surfactant. Here, we demonstrate that by extruding the emulsion through a needle immersed in a perfluorinated oil on top of which a coagulating aqueous bath is stratified and by applying a pulsed electrical field (panel a), it is possible to precisely control the size of the emulsion droplets detached from the needle. As soon as the emulsion droplets reach the interface between the perfluorinated oil and coagulating bath, they instantaneously solidify. An inverse relationship exist between intensity of the applied voltage and beads dimension (panels c,d,e). The presented process is very repeatable and brings about to beads rigorously monodisperse in size (panel f). Finally, such microbeads demonstrated to be a successful cell carrier.