Complete integration of microfluidic and optical functions in a single lab-on-chip device is one goal of optofluidics. Here, we demonstrate the hybrid integration of a PDMS-based fluid handling layer with a silicon-based optical detection layer in a single optofluidic system. The optical layer consists of a liquid-core antiresonant reflecting optical waveguide (ARROW) chip that is capable of single particle detection and interfacing with optical fiber. Integrated devices are reconfigurable and able to sustain high pressures despite the small dimensions of the liquid-core waveguide channels. We show the combination of salient sample preparation capabilities—particle mixing, distribution, and filtering—with single particle fluorescence detection. Specifically, we demonstrate fluorescent labelling of λ-DNA, followed by flow-based single-molecule detection on a single device. This points the way towards amplification-free detection of nucleic acids with low-complexity biological sample preparation on a chip.

A type of integrated hollow core waveguide with low intrinsic photoluminescence fabricated with Ta 2 O 5 and SiO 2 films is demonstrated. Hollow core waveguides made with a combination of plasma-enhanced chemical vapor deposition SiO 2 and sputtered Ta 2 O 5 provide a nearly optimal structure for optofluidic biofluorescence measurements with low optical loss, high fabrication yield, and low background photoluminescence. Compared to earlier structures made using Si 3 N 4 , the photoluminescence background of Ta 2 O 5 based hollow core waveguides is decreased by a factor of 10 and the signal-to-noise ratio for fluorescent nanobead detection is improved by a factor of 12.

Abstract:We report size-based sorting of micro-and sub-micron particles using optical forces on a planar optofluidic chip. Two different combinations of fluid flow and optical beam directions in liquid-core waveguides are demonstrated. These methods allow for tunability of size selection and sorting with efficiencies as high as 100%. Very good agreement between experimental results and calculated particle trajectories in the presence of flow and optical forces is found.

Over the past decade, optofluidics has established itself as a new and dynamic research field for exciting developments at the interface of photonics, microfluidics, and the life sciences. The strong desire for developing miniaturized bioanalytic devices and instruments, in particular, has led to novel and powerful approaches to integrating optical elements and biological fluids on the same chip-scale system. Here, we review the state-of-the-art in optofluidic research with emphasis on applications in bioanalysis and a focus on waveguide-based approaches that represent the most advanced level of integration between optics and fluidics. We discuss recent work in photonically reconfigurable devices and various application areas. We show how optofluidic approaches have been pushing the performance limits in bioanalysis, e.g. in terms of sensitivity and portability, satisfying many of the key requirements for point-of-care devices. This illustrates how the requirements for bianalysis instruments are increasingly being met by the symbiotic integration of novel photonic capabilities in a miniaturized system.

Optofluidic waveguides have been integrated with solid core waveguides on silicon using an antiresonant reflecting optical waveguide (ARROW) design. Interface transmission between solid and liquid core waveguides is one of the most important factors for overall optical throughput. The optimization of interface transmission by adjusting the thickness of top waveguide cladding layers was demonstrated experimentally and theoretically. The measured coupling efficiency increases from 18% to 67% and the overall throughput was improved due to improved mode matching while liquid core waveguides maintain a low average loss coefficient.