Dual production of biconvex polymer particles via surfactant-laden microfluidic ternary droplets

Lens-shaped particles with uniform size and precisely controlled shape are essential for applications ranging from controlled self-assembly to advanced micro-optical elements. We present a microfluidic method for generating surfactant-laden ternary droplets that enables the simultaneous fabrication of two biconvex polymeric particles with independently controlled sizes and shapes. This approach uses two photocurable acrylate monomer streams, separated by a non-curable silicone oil stream containing a surfactant, which are emulsified into nanoliter-sized ternary droplets within an aqueous polyvinyl alcohol solution. Minimizing interfacial energies results in stable ternary droplets comprising two biconvex monomer segments that are partially exposed to the external solution and separated by a biconcave non-curable segment. Off-chip photopolymerization of this droplet morphology produces two biconvex polymer particles from a single precursor droplet, effectively doubling the production yield compared to that of surfactant-laden Janus droplets. By precisely adjusting the flow-rate ratios, we achieved flexible control over the shape and size of the monomer segments, allowing for the tailored production of biconvex polymer particles. This versatile and efficient technique shows significant promise for advancing the development of specialized micro-optical elements and other functional materials, particularly in optics and imaging.