The development of a polydimethylsiloxane (PDMS) microfluidic microbeads trapping device is reported in this paper.
Besides fluid channels, the proposed device includes a pneumatic control chamber and a beads-trapping chamber with a
filter array structure. The pneumatic flow control chamber and the beads-trapping chamber are vertically stacked and
separated by a thin membrane. By adjusting the pressure in the pneumatic control chamber, the membrane can either be
pushed against the filter array to set the device in "trapping mode" or be released to set the device in "releasing mode".
In this paper, a computational fluid dynamics simulation was conducted to optimize the geometry design of the filter
array structure; the device fabrication was also carried out. The prototype device was tested and the preliminary
experimental results showed that it can be used as a beads-trapping unit for various biochemistry and analytical
chemistry applications, especially for flow injection analysis systems.
In this paper, we report the design and fabrication of a pre-aligned free-space optical interconnection
(FSOI) device. A simple FSOI prototype device is designed based on Gaussian beam propagation
calculation. All optical components of a FSOI device were designed in a single one mask, and the
alignment between the optical components was achieved in the mask design stage. All optical components
including microlens array and micro mirrors were positioned in an out-of-plane fashion. The fabrication
was based on a tilted Ultraviolet (UV) lithography of the SU-8 mold and fast replication using a UV
curable polymer. This method allows the production of integrated optical systems similar to conventional
optical benches in microscale and eliminates the need for tedious high-precision assembly.
In this paper, we describe the design and fabrication of a polydimethylsiloxane (PDMS) microchip for on-chip
multiplex immunoassay applications. The microchip consists of a PDMS microfluidic channel layer and a micro
pneumatic valve control layer. By selectively pressurizing the pneumatic microvalves, immuno reagents were controlled
to flow and react in certain fluidic channel sites. Cross contamination was prevented by tightly closed valves. Our design
was proposed to utilize PDMS micro channel surface as the solid phase immunoassay substrate and simultaneously
detect four targets antigens on chip. Experimental results show that 20psi valve pressure is sufficient to tightly close a
200μm wide micro channel with flow rate up to 20μl/min.
This paper presents a micro flow cytometry device fabricated using Ultra Violet (UV) lithography of the negative tone
photo resist SU-8. A diamond-shaped sample injection nozzle, a three-dimensional hydro-focusing unit, and an optical
detection unit with integrated out-of-plane microlens were fabricated using tilting lithography techniques. In addition to
a 60° horizontal focusing angle, 30° slopes were designed and fabricated in the vertical direction of the hydro-focusing
chamber. This unique design makes the hydro-focusing unit presented in this paper a truly three-dimensional one instead
of the two-dimensional ones usually reported in literature. In the optical detection unit, a multi mode optical fiber was
used to collect fluorescent or scattering light from the sample. To improve detection efficiency, out-of-plane microlens
made of cured SU-8 polymer was imbedded in one of the outlet fluid channel walls. Numerical simulations were
conducted to analyze the optical system and optimize the distances between optical elements to achieve best light
coupling efficiency using commercial optical design software Zemax.
This paper presents the design and fabrication of an integrated cell counter for a MEMS flow cytometer. The
imbedded out-of-plane micro lens in the cell counter is used to focus the fluorescent or scattering light emitting from
the dyed cells into the output fiber to improve the optical detection efficiency. Both the optical cell counter device
with imbedded micro-lens and the hydro-focusing unit of the micro flow cytometer were fabricated using a process
based on UV lithography of SU-8 negative-tone photoresist. A novel microfabrication technology based on tilted
UV-lithography and controlled exposure dosage and development time was performed to produce the out-of-plane
micro lens. Out-of-plane micro lens with various pad sizes and focal lengths can be fabricated by carefully
controlling the fabrication process. The microlens and the hydrofocusing unit were fabricated using the same mask.
High alignment accuracy can therefore be achieved without any post-fabrication alignment processes.