Optical Manipulation of Whispering Gallery Mode Microlasers for Precision Controlled Cellular Delivery

Whispering gallery mode microlasers are known for their high Q-factors, characteristic emission spectra and sensitivity to local refractive index changes. This sensitivity combined with the ability of various cell types to internalise these microlasers provide unique opportunities for advanced biological studies, e.g. in single-cell tracking and intracellular sensing. Despite many advancements, achieving precise delivery of lasers to cells remains challenging, with traditional methods, such as microinjection, often also resulting in cellular damage. Here, we show that optical trapping is a promising solution for microlaser manipulation and therefore for their controlled and non-invasive delivery to target cells. By integrating optical trapping with microlaser-based refractive index sensing, we study the dynamics of microlaser-uptake by cells. We also find that in some cases the peaks in the emission spectra of our microlasers broaden, split, and shift, and we assign this to local inhomogeneities in refractive index surrounding the microlaser. This shows how optical trapping can further expand the unique toolkit offered by biointegrated whispering gallery mode microlasers.