Victor Lien

Fluidic adaptive lens with high focal length tunability

Fluidic adaptive lenses with an adjustable focal length over a wide range were demonstrated in this letter. The focal length adjustment was achieved by changing the shape of the fluidic lens without any mechanical moving parts. The shortest focal length demonstrated in such devices is 41 mm, which corresponds to a large numerical aperture of 0.24 and a small F number of 2.05. The highest resolution measured using a positive standard is 25.39 lp/mm in this fluidic adaptive lens.

Demonstration of two-dimensional fluidic lens for integration into microfluidic flow cytometers

The focusing capabilities of a two-dimensional fluid-filled lens microfabricated in an optical polymer are demonstrated. The illumination path is visualized by localized scattering centers. Functionality for flow cytometry applications is demonstrated by localization of the excitation of large-angle scatter. Integrated in-plane optical systems offer simple, compact, and inexpensive alternatives to external optics, as well as the potential for increased detection efficiency and low-power operation.

A prealigned process of integrating optical waveguides with microfluidic devices

We present a novel technology to monolithically integrate buried heterostructure waveguides with microfluidic channels in a prealigned manner. The fabrication process produced sealed microfluidic channels, low-loss waveguides, and excellent waveguide-channel alignment. The resultant device allows efficient optical coupling between the channels and the waveguides. Thus, the waveguides can both deliver the optical power and collect the emitted light.

High-performance fluidic adaptive lenses

High-performance fluidic lenses with an adjustable focal length spanning a very wide range (30 mm to infinite) are demonstrated. We show that the focal length, F-number, and numerical aperture can be dynamically controlled by changing the shape of the fluidic adaptive lens without moving the lens position mechanically. The shortest focal length demonstrated is less than 30 mm for a 20-mm lens aperture. The fluidic adaptive lens has a nearly perfect spherical profile and shows a resolution better than 40 line pairs/mm in a plano-convex structure and 57 line pairs/mm in a biconvex structure.

High-sensitivity cytometric detection using fluidic-photonic integrated circuits with array waveguides

We demonstrate a new detection scheme for a microfabricated flow cytometer. The fluidic-photonic integrated circuits (FPICs) that perform flow cytometric detection possess new functionality, such as on-chip excitation, time-of-flight measurement, and above all, greatly enhanced fluorescence detection sensitivity. Using the architecture of space-division waveguide demultiplexer and the technique of cross-correlation analysis, we obtained high detection sensitivity with a simple light source and a detector, without high-power laser excitation and lock-in amplifier (or photomultiplier tube) detection. Besides improving cytometric detection, the technology of integrating microfluidic circuits with photonic circuits into the FPIC presents a new platform for sophisticated biomedical-sensing devices with significant cost, size, and performance advantages.

Universally applicable three-dimensional hydrodynamic microfluidic flow focusing

We have demonstrated a microfluidic device that can not only achieve three-dimensional flow focusing but also confine particles to the center stream along the channel. The device has a sample channel of smaller height and two sheath flow channels of greater height, merged into the downstream main channel where 3D focusing effects occur. We have demonstrated that both beads and cells in our device display significantly lower CVs in velocity and position distributions as well as reduced probability of coincidental events than they do in conventional 2D-confined microfluidic channels. The improved particle confinement in the microfluidic channel is highly desirable for microfluidic flow cytometers and in fluorescence-activated cell sorting (FACS). We have also reported a novel method to measure the velocity of each individual particle in the microfluidic channel. The method is compatible with the flow cytometer setup and requires no sophisticated visualization equipment. The principles and methods of device design and characterization can be applicable to many types of microfluidic systems.

Fluidic photonic integrated circuit for in-line detection

We present a microfabricated fluidic photonic integrated circuit (FPIC) performing the detection function for flow cytometry. This device was entirely made of polymer using micromolding and capillary filling techniques. An array waveguide design was chosen to achieve superb sensitivity and the time-of-flight measurement for each particle flowing by. With multichannel sampling and cross-correlation analysis, the results show significant enhancement of detection sensitivity.

Scattering-Based Cytometric Detection Using Integrated Arrayed Waveguides With Microfluidics

Scattering-based on-chip excitation and detection on the arrayed-waveguide platform has been developed and implemented. Detected signals were processed with the proposed multiplication-based cross-correlation algorithm. The algorithm is capable of not only achieving signal enhancement (80 dB relative to the untreated signals) but also velocity measurement. Thus, particles flowing at different speed could also be accurately detected. Processed signals were verified by comparison to frame-by-frame video images, showing excellent correspondence. The signal processing algorithm can be easily extended to real-time on-chip detection

Microspherical surfaces with predefined focal lengths fabricated using microfluidic capillaries

We demonstrate a technique to fabricate spherical micromirrors with a programmable focal length by microfluidic capillary. Micromirrors with focal lengths of 13 μm, 19 μm, 28 μm, 50 μm, and a flat mirror were fabricated and characterized. These micromirrors show a great ability to converge light into a focal point. This technique also introduces the concept of fabricating and integrating optical components with microfluidic channels.

Integrated Fluidic Photonics for Multi-Parameter In-Plane Detection in Microfluidic Flow Cytometry

Cylindrical fluid-filled lenses microfabricated in polydimethylsiloxane (PDMS) polymer are incorporated into a microfluidic flow cytometer to localize excitation in the channel and enable multi-parameter in-plane scatter detection