| Summary: | Optofluidics describes a relatively new area of research that aims to synergistically combine optics and fluidics technologies. In this work, we examine the application and integration of small fluid volumes into two types of optical devices, yielding improvements in either tunability, flexibility, or cost-effectiveness. First, we explore a simple methodology to dispense and shape water droplets for use as the magnifying element in a microscope operating under either reflection-mode or transmission-mode illumination. A water droplet is created at the end of a syringe and then coated with a thin layer of silicone oil to mitigate evaporation. By applying mechanical pressure to the water droplet using a metal tip, the shape of the droplet is tuned to yield focusing properties amenable for microscopy. Images captured using the microscope demonstrate micron-scale resolution, variable magnification, and imaging quality comparable to that obtained by a conventional, laboratory-grade microscope. Next, we develop a surface plasmon resonance (SPR) sensor that exploits the index matching and coating capabilities of fluids. Conventional SPR sensor are implemented using an external light source, optical components to polarize incident light and guide light to and from a metal surface, a coupling device (such as a prism) to convert free-space light into surface plasmons on a metal surface and back into free-space light, and a light detector. Here, we develop a new SPR device architecture by combining several optical components via index matching fluid, which eliminates the need for a prism and integrates light delivery, light polarization control, surface plasmon coupling onto a thin, flexible substrate. We experimentally characterize the SPR device and find good agreement between experimental reflectivity measurements and a theoretical reflectivity model based on transfer-matrix formalism. By developing these new methods to integrate fluids for both microscopy and optical sensing applications, this work provides results that highlight both the promise and challenges of creating optical systems based on fluids.
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