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Topic Name: Researchers for the first time have integrated Optical Functions with Microfluidic ones
Category: Adaptive Optics
Research persons: Michal Lipson,David Erickson
Location: Cornell University, United States
Details
Researchers at Cornell University for
the first time have integrated optical functions with microfluidic ones,
enabling the sorting of particles by light. Reported in the Oct. 29 issue of
Optics Express, due out Monday, the Cornell team showcases a new design for a
"lab-on-a-chip" structure that provides the ability to move or sort
particles using light. In addition to the advance in telecom and datacom
applications this brings, the new architecture also lends itself to applications
in biodetection, including the sorting of viruses and protein recognition.
Summary
This novel architecture, created by lead researcher Michal Lipson and her
group and David Erickson and his group, is made up of a field of solid core
waveguides. The waveguides are fabricated from SU-8, a material whose mechanical
hardness and chemical resistance make it a source for use in lab-on-chip
analysis systems. The waveguides used in the device achieve a much more
efficient sorting process, which enables trapping and sorting much smaller
spheres with much lower intensities than what has been previously reported. By
integrating these waveguides on a chip, a massive parallel sorting system may be
created. This sorting system would allow for hundreds of measurements in
parallel on a 1x1 cm chip, introducing a portable system that provides greater
efficiency and lower cost than the current methodologies.
Key Findings
- This is the first demonstration of complete integration of planar optical
waveguides with microfluidic ones.
- This integrated system allows researchers to use light to control the
movement of particles in a pressure-driven flow.
- The planar optofluidic architecture developed represents a simple yet
functional optical manipulation system for lab-on-chip applications.
- The use of planar photonic structures in microfluidic devices removes the
need for table-top free-space optics, potentially reducing costs and
increasing platform portability.
- Such a system could find application in high-stability particle trapping
and sorting, but also in biodetection by exploiting the strong light
interaction between the particle and the evanescent field.
Paper
"Optofluidic trapping and transport on solid core waveguides within a
microfluidic device," Optics Express, Vol. 15, Issue 22, pages 14322-14334.
Note for waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves, light, or sound waves. There are different types of waveguide for each type of wave.
Electromagnetic waveguides
Waveguides can be constructed to carry waves over a wide portion of the electromagnetic spectrum, but are especially useful in the microwave and optical frequency ranges. Depending on the frequency, they can be constructed from either conductive or dielectric materials. Waveguides are used for transferring both power and communication signals.
Optical waveguides
Waveguides used at optical frequencies are typically dielectric waveguides, structures in which a dielectric material with high permittivity, and thus high index of refraction, is surrounded by a material with lower permittivity. The structure guides optical waves by total internal reflection. The most common optical waveguide is optical fiber.
Other types of optical waveguide are also used, including photonic-crystal fiber, which guides waves by any of several distinct mechanisms. Guides in the form of a hollow tube with a highly reflective inner surface have also been used as light pipes for illumination applications. The inner surfaces may be polished metal, or may be covered with a multilayer film that guides light by Bragg reflection (this is a special case of a photonic-crystal fiber). One can also use small prisms around the pipe which reflect light via total internal reflection —such confinement is necessarily imperfect, however, since total internal reflection can never truly guide light within a lower-index core (in the prism case, some light leaks out at the prism corners).
Note for SU-8
SU-8 is a commonly used negative photoresist. It is a very viscous polymer that can be spun or spread over a thickness ranging from 1 micrometer up to 2 millimeters and still be processed with standard mask aligner. It can be used to pattern high aspect ratio (>20) structures.[1] Its maximum absorption is for ultraviolet light with a wavelength of 365 nm. When exposed, SU-8's long molecular chains cross-link causing the solidification of the material.
SU-8 is mainly used in for fabrication of microfluidics and MEMS parts. It is also one of the most bio-compatible materials and is often used in
bio-MEMS.
Note for Microfluidics
Microfluidics deals with the behavior, precise control and manipulation of microliter and nanoliter volumes of fluids. It is a multidisciplinary field intersecting engineering, physics, chemistry, microtechnology and biotechnology, with practical applications to the design of systems in which such small volumes of fluids will be used. Microfluidics has emerged only in the 1990s and is used in the development of DNA chips, micro-propulsion, micro-thermal technologies, and lab-on-a-chip technology.
Key application areas
Advances in microfluidics technology are revolutionizing molecular biology procedures for enzymatic analysis (e.g., glucose and lactate assays), DNA analysis (e.g., polymerase chain reaction and high-throughput sequencing), and proteomics. The basic idea of microfluidic biochips is to integrate assay operations such as detection, as well as sample pre-treatment and sample preparation on one chip.
An emerging application area for biochips is clinical pathology, especially the immediate point-of-care diagnosis of diseases. In addition, microfluidics-based devices, capable of continuous sampling and real-time testing of air/water samples for biochemical toxins and other dangerous pathogens, can serve as an always-on "bio-smoke alarm" for early warning.
About Researchers:
Michal Lipson
Electrical and Computer Engineering
Assistant Professor
411 Phillips Hall
Ithaca, NY 14853
Phone: (607) 255-7877
Fax: (607) 254-3508
Email: ml292@cornell.edu
Current Research Projects
- Compact Fiber to Waveguide Couplers
- Quantum Dot Photonics
- Silicon Nanotransistor
- Small-size Low-Consumption and High-Modulation-Depth
Silicon Electro-Optic Switch
- Slot-waveguide for strong confinement of light in low-index
materials
- Photonics for Biosensing
David J. Erickson
Oak Ridge National Laboratory
Bethel Valley Rd.
POBox 2008, Bldg 5600
Oak Ridge, TN 37831-6016
Phone: (865) 574-3136
Fax: (865) 574-0680
Email: ericksondj@ornl.gov
David Erickson is Director of the Climate and Carbon Research Institute in the Center for Computational Sciences and is a senior research staff member in the Climate Dynamics Group in the Computer Science and Mathematics Division at Oak Ridge National Laboratory.
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