Controlling the size and elastic modulus of in-aqueous alginate micro-beads

The fabrication of microgels, particularly those ranging from tens to hundreds of micrometers in size, represents a thriving area of research, particularly for biologists seeking controlled and isotropic media for cell encapsulation. In this article, we present a novel and robust method for producing structurally homogeneous alginate beads with a reduced environmental footprint, employing a co-flow focusing microfluidic device. These beads can be easily recovered in an oil-free aqueous medium, making the fabrication method highly suitable for diverse applications. We demonstrate precise control over the production of perfectly spherical beads across a wide range of diameters, from about 30 to 300 μm. We then measure Young's moduli of the beads, revealing a wide accessible range from 90 Pa to 11 kPa, contingent upon controlling the type (e.g. chain length) and concentration of alginate.