Fabrication of Photonic Microlasers via Microfluidic Double Emulsion

Abstract

Abstract Fluid control at a micro-level features unique properties that can be utilized to develop devices capable of biosensing. Microfluidics is a branch of technology that deals with microfluidic channels and the fluids confined within those channels. Singular droplets can be produced when perpendicular streams of immiscible fluids intersect with the main fluid stream. This intersecting stream must be different than the main fluid stream. One fundamental way of fabricating the spheres includes using a stream of water and oil. As oil and water do not mix, the stream of oil will separate the water stream and release a singular droplet. Photonic spherical microlasers manufactured by microfluidic systems exhibit a more consistent size control and are mass-produced easily; by controlling the pressure or flow rate of both dispersed phase and continuous phase, the size of the microlaser can be precisely controlled. The use of microlasers can open several paths toward susceptible sensing systems in a variety of biomedical applications, such as cancer detection and nerve cell electric potential detection via voltage-sensitive dyes. In the past, such sensing systems have been created using different UV curable biocompatible polymers doped with laser dyes. In this work, we consider testing various configurations of immiscible fluids for the disperse and continuous phases. Not only that, but the use of double emulsion microlasers will be advantageous over single emulsion types due to a promising increase of versatility in terms of multiplexed sensing and broad applications. This new solution involves microfluidic pumps and a flow-focusing droplet generator chip with microfluidic channels fabricated with polydimethylsiloxane (PDMS) and polycarbonate. Factors like the flow rate (Q) and pressure (P) of both continuous and dispersed phases determine the size of both the core and shell of these double emulsion droplets, which are made solid-state via the UV curing process. These sensors involve the whispering-gallery-mode phenomenon, where laser light is coupled to the microlaser generating optical resonances; the incoming photons resonate because light waves propagate throughout the inner walls of the sphere. This resonance can be shifted due to external conditions that change the traveling light’s optical path. The changes in the optical spectrum are monitored by using an optical spectrometer. Such sensors have the potential to be implemented as point-of-care (POC) devices and have the prospect of growing and becoming an impactful technology in biomedical research and industry.