Tor Vestad

Microfluidic sorting system based on optical waveguide integration and diode laser bar trapping

Effective methods for manipulating, isolating and sorting cells and particles are essential for the development of microfluidic-based life science research and diagnostic platforms. We demonstrate an integrated optical platform for cell and particle sorting in microfluidic structures. Fluorescent-dyed particles are excited using an integrated optical waveguide network within micro-channels. A diode-bar optical trapping scheme guides the particles across the waveguide/micro-channel structures and selectively sorts particles based upon their fluorescent signature. This integrated detection and separation approach streamlines microfluidic cell sorting and minimizes the optical and feedback complexity commonly associated with extant platforms.

Optical trapping, manipulation, and sorting of cells and colloids in microfluidic systems with diode laser bars.

We demonstrate a new technique for trapping, sorting, and manipulating cells and micrometer-sized particles within microfluidic systems, using a diode laser bar.

Flow control for capillary-pumped microfluidic systems

Advantages of performing analytical and diagnostic tasks in microfluidic-based systems include small sample volume requirements, rapid transport times and the promise of compact, portable instrumentation. The application of such systems in home and point-of-care situations has been limited, however, because these devices typically require significant associated hardware to initiate and control fluid flow. Capillary-based pumping can address many of these deficiencies by taking advantage of surface tension to pull fluid through devices. The development of practical instrumentation however will rely upon the development of precision control schemes to complement capillary pumping. Here, we introduce a straightforward, robust approach that allows for reconfigurable fluid guidance through otherwise fixed capillary networks. This technique is based on the opening and closing of microfluidic channels cast in a flexible elastomer via automated or even manual mechanical actuation. This straightforward approach can completely and precisely control flows such as samples of complex fluids, including whole blood, at very high resolutions according to real-time user feedback. These results demonstrate the suitability of this technique for portable, microfluidic instruments in laboratory, field or clinical diagnostic applications.

Flow resistance for microfluidic logic operations

Control of relative flow resistance is used for the actuation of both one- and two-input microfluidic “logical gates”. By taking advantage of system nonlinearities and despite the linear response of laminar flows associated with these length scales, a number of operators including the NOT, AND, OR, XOR, NOR, and NAND are demonstrated. Because these gates can be actuated simultaneously they can be combined to form more complicated devices such as a half adder. This approach is therefore flexible and illustrates that any macro- or microscale technique that can alter flow resistance can be used as the basis of a fluid-based logical micro-operator.

Optical waveguides via viscosity-mismatched microfluidic flows

This letter describes all-liquid optical waveguiding within microfluidic channels that employs viscosity-mismatched core and cladding fluids. Efficient optical coupling is achieved through superior control of fluid flow profiles obtained via hydrodynamic focusing and models describing the control of the viscosity-mismatched, graded index fluid waveguides are presented. As a demonstration of this approach, a fluorescence quantification assay is performed using dyed colloidal particles.

Three-dimensional chemical concentration maps in a microfluidic device using two-photon absorption fluorescence imaging

Two-photon absorption fluorescence is employed within a microfluidic device to create a three-dimensional chemical concentration map for mixing uniformity characterization. This multiphoton technique images fluorescence intensity directly and provides a simple, rapid, and readily employed route to composition characterization within microfluidic systems.

Optically integrated microfluidic systems for cellular characterization and manipulation

Expanding interest in microfluidic techniques for biomedical applications has driven the recent need for micro-integrated optics capable of both traditional characterization and emerging optical manipulation techniques. We discuss here how ultrafast laser micromachining can be used to create optical waveguides directly within microfluidic systems. We then utilize this fabrication approach to create a unique microfluidic platform for optical characterization and sorting of cells and particles. This new platform employs optically fabricated waveguides to scatter and refract light from individual particles, allowing accurate in situ size detection and sorting within a microfluidic channel.

Two-photon absorption fluorescence imaging to characterize microfluidic device performance

Two-photon absorption fluorescence imaging is used to quantitatively measure 3D flow and mixing in microfluidics. This is an important characterization tool for developing optimal microfluidic devices for use in the study of biological molecular dynamics.

Compact, rapid cell deformability measurements using diode laser bar optical trapping in microfluidics

We present a simple, compact, microfluidic system that easily facilitates diode laser bar optical trapping for cell stretching measurements and particle sorting within flowing microfluidic systems for the first time.

Integrated, all-optical, particle characterization and sorting in microfluidic systems

We demonstrate an integrated, microfluidic, all-optical characterization and sorting system. The integrated optical system is created by femtosecond micromachining, and the particle manipulation is performed with a novel optical trapping system.