We demonstrate a small device with a microfluidic channel and an integrated waveguide that functions a compact
rudimentary tool for the detection, real-time monitoring, and potentially classification of algae. In order to reduce
parasitic noise the micro-device used a curved subsurface optical waveguide to illuminate particles transiting through a
microfluidic channel. The changes in the transmitted signal are monitored using a quadrant-cell photo-detector. The
signals wavelets from the different quadrants are used to qualitatively distinguish different families of algae. Additional
information, such as flow direction, is also provided. The channel and waveguide are fabricated out of a monolithic
fused-silica substrate using a femtosecond laser-writing process combined with chemical etching. This proof-of-concept
device paves the way for more elaborate femtosecond laser-based optofluidic micro-instruments incorporating
waveguide network designed for the real-time analysis of cells and microorganisms in the field.
We demonstrate a small device with a microfluidic channel and an integrated waveguide as a compact rudimentary tool
for the detection, real-time monitoring, and potentially classification of algae. In order to reduce parasitic noise the
micro-device used a curved subsurface optical waveguide to illuminate particles transiting through a microfluidic
channel. The changes in the transmitted signal are monitored using a quadrant-cell photo-detector. The signals wavelets
from the different quadrants are used to qualitatively distinguish different families of algae. Additional information, such
as flow direction, is also provided. The channel and waveguide are fabricated out of a monolithic fused-silica substrate
using a femtosecond laser-writing process combined with chemical etching. This proof-of-concept device paves the way
for more elaborate femtosecond laser-based optofluidic micro-instruments incorporating waveguide network designed
for the real-time analysis of cells and microorganisms in the field.
Optical waveguides used as a local light source along a fluidic channel have proven to be an effective approach
to detecting cells in the field of flow-cytometry. One challenge, however, has been a simple integration of
optical waveguides with the fluidic channel. We employ the use of femtosecond laser-writing process to pattern a
waveguide in the bulk of a fused-silica glass substrate housing a fluidic channel. We demonstrate an in-situ scheme
for detecting sub-millimeter components based on such a monolithically fabricated device. By illuminating the
waveguide and collecting the light signal past the channel, we detect opaque and transparent components between
300 - 500 μm in size, as each moves along the channel. Both an opaque square chip and a transparent bead
attentuate the signal by more than 95% primarily due to reflection and refraction respectively. The signature
of a transparent bead additionally shows attenuated peaks which we attribute to normal incidence of light from
the waveguide. The projected sizes of the parts are determined with less than 1% uncertainty. We conclude that
the femtosecond laser produced waveguides in fused-silica glass are a viable option for the detection of certain
kinds of sub-millimeter components. This approach holds the prospects of fabricating complex three-dimensional
networks of waveguides monolithically.
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