Micromachining technology was used to prepare chemical analysis systems on glass chips (1 centimeter by 2 centimeters or larger) that utilize electroosmotic pumping to drive fluid flow and electrophoretic separation to distinguish sample components. Capillaries 1 to 10 centimeters long etched in the glass (cross section, 10 micrometers by 30 micrometers) allow for capillary electrophoresis-based separations of amino acids with up to 75,000 theoretical plates in about 15 seconds, and separations of about 600 plates can be effected within 4 seconds. Sample treatment steps within a manifold of intersecting capillaries were demonstrated for a simple sample dilution process. Manipulation of the applied voltages controlled the directions of fluid flow within the manifold. The principles demonstrated in this study can be used to develop a miniaturized system for sample handling and separation with no moving parts.

Micromachining a miniaturized capillary electrophoresis-based chemical analysis system on a chip

A key requirement for astronomical instruments in next generation Extremely Large Telescopes (ELTs) is the
development of large-aperture Integral Field Units (IFUs) that enable the efficient and spatially contiguous sampling of
the telescope image plane for coupling stellar light onto a spectrometer Current IFUs are complex to fabricate and suffer
from stray light issues, which limits their application in high-contrast studies such as exoplanet imaging In this paper,
we present our work on the development of freeform microlens arrays using the rapidly maturing technique of ultrafast
laser inscription and selective wet chemical etching Using the focus spot from a femtosecond laser source as a tool with
an essentially unrestricted “tool-path”, we demonstrate that it is possible to directly write the surface of a lenslet in three
dimensions within the volume of a transparent material We further show that high surface quality of the lenses can be
achieved by using an oxy-natural gas flame to polish the lens surface roughness that is characteristic of the post-etched
structures Using our technique, the shape and position of each lenslet can be tailored to match the spatial positioning of
a two-dimensional multimode fiber array, which can be monolithically integrated with the microlens array

Towards freeform microlens arrays for near infrared astronomical instruments

Optical forces offer a powerful tool for manipulating single cells noninvasively. Integration of optical functions within microfluidic devices provides a new freedom for manipulating and studying biological samples at the micro scale. In the pursuit to realise such microfluidic devices with integrated optical components, Ultrafast Laser Inscription (ULI) fabrication technology shows great potential. The uniqueness and versatility of the technique in rapid prototyping of 3D complex microfluidic and optical elements as well as the ability to perform one step integration of these elements provides exciting opportunities in fabricating novel devices for biophotonics applications. The work described in this thesis details the development of three dimensional optofluidic devices that can be used for biophotonics applications, in particular for performing cell manipulation and particle separation. Firstly, the potential of optical forces to manipulate cells and particles in ULI microfluidic channels is investigated. The ability to controllably displace particles within a ULI microchannel using a waveguide positioned orthogonal to it is explored in detail. We then prototype a more complex 3D device with multiple functionalities in which a 3D optofluidic device containing a complex microchannel network and waveguides was used for further investigations into optical manipulation and particle separation. The microfluidic channel network and the waveguides within the device possess the capability to manipulate the injected sample fluid through hydrodynamic focusing and optically manipulate the individual particles, respectively. This geometry provided a more efficient way of investigating optical manipulation within the device. Finally, work towards developing a fully optimised 3D cell separator device is presented. Initial functional validation was performed by investigating the capability of the device to route particles through different outlet channels using optical forces. A proof of concept study demonstrates the potential of the device to use for cell separation based on the size of the cells. It was shown that both passive and active cell separation is possible using this device. To my parents and brother

Three dimensional optofluidic devices for manipulation of particles and cells

A wide variety of techniques have been developed for fabricating microfluidic and optofluidic components and devices using polymer, glass, and silicon substrates. This chapter gives a brief overview of these techniques, which can be categorized into two classes: parallel processing techniques based on photolithography and serial processing techniques based on direct writing. Some representative examples of these two categories are discussed, including photolithography on glass, soft lithography on poly(dimethylsiloxane) (PDMS), and femtosecond-laser-induced two-photon polymerization. The main advantages and disadvantages of parallel and serial processing are compared. Polymers are currently the most commonly used material for microfluidic and optofluidic applications because fabrication in polymers is easy, rapid, and cost effective. In contrast, glass offers better chemical durability and optical performance. Femtosecond laser direct writing enables microfluidic and integrated optofluidic structures with complex three-dimensional geometries to be directly embedded in glass, eliminating the need to use multistep procedures such as stacking and bonding.

Koji Sugioka

Papers

Current Techniques for Fabricating Microfluidic and Optofluidic Devices