Spatially selective fixed-optics multicolor fluorescence detection system for a multichannel microfluidic device, and method for detection
Inventors
Morgan, Nicole Y. • Smith, Paul • Wellner, Ed
Assignees
US Department of Health and Human Services
Publication Number
US-7924425-B2
Publication Date
2011-04-12
Expiration Date
2026-06-26
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Abstract
A system for spatially selective, fixed-optics fluorescence detection in a multichannel polymeric microfluidic device, and a method for performing spatially selective, fixed-optics fluorescence detection.
Core Innovation
The invention relates to a system and method for spatially selective, fixed-optics laser-induced fluorescence detection in a multichannel polymeric microfluidic device. It provides sensitive, spatially resolved, and spectrally resolved fluorescence detection from multiple microfluidic channels, with the capability of detecting multiple fluorescence colors in each microchannel. The detection system uses fixed optical parts without moving components, enabling robust and versatile parallel analysis.
The problem being solved is to overcome the challenges posed by fluorescence detection in plastic or polymeric microfluidic devices, where the plastic substrate exhibits its own fluorescence background that reduces sensitivity. Conventional confocal systems, while spatially selective, are complex, expensive, and require mechanical scanning for multiple channels. Ball lens systems provide simplicity but have very short working distances and suffer from background interference. Hence, there is a need for a simple, inexpensive, fixed-optics system that allows multiplexed measurements with spatial selectivity in plastic microchips.
Claims Coverage
The claims include two independent claims directed to a spatially selective fluorescence detection system with a single optical fiber and ball lens, and a system comprising multiple such assemblies for multichannel detection, as well as a claim for a related method. The inventive features cover the specific optical arrangements, positioning, and components enabling improved fluorescence detection.
Ball lens and optical fiber arrangement for spatially selective fluorescence detection
The system comprises an optical fiber and a ball lens mounted adjacent to one end of the fiber. The ball lens has a diameter larger than the fiber and is spaced by a first distance greater than its radius such that emitted light from a spatially selected volume converges onto the fiber end. The first distance is chosen so that a circle of transmitted light defined by the intersection of a marginal transmitted ray and the caustic has a diameter equal to that of the fiber. This arrangement enables focused collection of fluorescence with spatial selectivity.
Matching acceptance angle of optical fiber and positioning of sample volume
An angle of the marginal transmitted ray as it enters the optical fiber equals the maximum acceptance angle of the fiber, and a second distance between the edge of the ball lens and the spatially selected volume is positioned to maximize transmitted intensity from the source. The selected volume typically lies within a microfluidic channel or flow cell and has lateral and height dimensions comparable to the channel.
Use of multiple ball lens-optical fiber pairs for multichannel detection
The system extends to multiple optical fibers and respective ball lenses arranged with the same spatial selectivity principles, enabling simultaneous detection from multiple spatially selected volumes (e.g., multiple microchannels). The ball lenses and fiber ends are mounted on a holder that fixes their relative positions to maintain optimal optical geometry and working distances.
Excitation beam manipulation for multichannel fluorescence excitation
The system includes means for splitting a single laser excitation beam into multiple focused spots using a pair of cylindrical lenses and an array of plano-convex lenses in a linear arrangement. Each focused spot targets a different spatially selected volume (microchannel), enabling efficient parallel excitation without scanning.
Method for analyzing spatially selected volumes by fluorescence
The method involves positioning multiple ball lenses adjacent to selected volumes of a microfluidic device, each coupled to an optical fiber at an optimized distance, enabling simultaneous measurement of fluorescence spectra with spatial selectivity and high collection efficiency. The spatial arrangement matches the circle of transmitted light to the fiber diameter for optimal coupling.
The claims cover the innovative optical configuration of ball lenses and fibers positioned for spatially selective fluorescence detection from microfluidic devices, both in single and multichannel setups, including methods and excitation beam arrangements to enable parallel, fixed-optics fluorescence detection.
Stated Advantages
Provides sensitive, spatially resolved and spectrally resolved fluorescence detection from multiple microfluidic channels simultaneously without moving parts, making the system more robust and versatile.
Enables greater working distance compared to conventional ball lens systems, allowing focus at or near the center of microchannels even with typical sealing layer thicknesses.
Delivers spatial selectivity to isolate fluorescence originating within microchannels from background substrate fluorescence in plastic microchips without requiring complex confocal optics.
Allows multiplexed measurements in microfluidic devices, increasing throughput and saving instrument and operator time.
Uses a simple and inexpensive fixed-optics design suitable for mass production and easy alignment.
Documented Applications
Fluorescence or luminescence detection in microchip-based analysis for DNA analysis, proteins, and other biomolecules.
Biomedical, clinical, and biomedical research analyses using polymeric microfluidic devices.
Separation-based analyses such as chromatography and electrophoresis of nucleic acids, proteins, and other molecules of biomedical interest.
Applicable to microfluidic devices formed from various polymeric materials, including polycarbonate, PMMA, polystyrene, and PET.
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