A Flexible Nanograting Integrated Onto Silicon Micromachines by Soft Lithographic Replica Molding and Assembly

Truxal, Steven C.; Tung, Yi-Chung; Kurabayashi, Katsuo

doi:10.1109/jmems.2008.918400

Cited by 11 publications

(9 citation statements)

References 33 publications

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“…Oxygen plasma treatment for the surfaces of the PDMS grating microbridge bottom and the silicon comb drives is used to promote permanent bonding. Our previous study17 shows that the PDMS-silicon bonding is strong enough to sustain more than 100 million cycles of operation.…”

Section: Methodsmentioning

confidence: 99%

“…(C) A plot of the real-time spectral signals from a flowing single green colored polystyrene microsphere (the maximum emission at λ = 523 nm) that is constructed from 5-sweep spectral measurements within 5 ms. The PMT signal data are converted to the spectral plots based on a strain–voltage calibration curve and the grating equation 17. Here, the PMT intensity is given in terms of the output signal voltage.…”

Section: Figuresmentioning

confidence: 99%

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Multiplexed Spectral Signature Detection for Microfluidic Color-Coded Bioparticle Flow

et al. 2010

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Here, we report a high-speed photospectral detection technique capable of discriminating subtle variations of spectral signature among fluorescently labeled cells and microspheres flowing in a microfluidic channel. The key component used in our study is a strain-tunable nanoimprinted grating microdevice coupled with a photomultiplier tube (PMT). The microdevice permits acquisition of the continuous spectral profiles of multiple fluorescent emission sources at 1 kHz. Optically connected to a microfluidic flow chamber via a multimode optical fiber, our multiwavelength detection platform allows for cytometric measurement of cell groups emitting nearly identical fluorescence signals with a maximum emission wavelength difference as small as 5 nm. The same platform also allows us to demonstrate microfluidic flow cytometry of four different microsphere types in a wavelength bandwidth as narrow as 40 nm at a high (>85%) confidence level. Our study shows that detection of fluorescent spectral signatures at high speed and high resolution can expand specificity of multicolor flow cytometry. The enhanced capability enables multiplexed analysis of color-coded bioparticles based on single-laser excitation and single-detector spectroscopy in a microfluidic setting. The fluorescence signal discrimination power achieved by the optofluidic technology holds great promise to enable quantification of cellular parameters with higher accuracy as well as enumeration of a larger number of cell types than conventional flow cytometric methods.Fluorescently color-coded cells, biomolecules, and microspheres enable multiparameter detection in disease screening, 1 molecular imaging, 2 DNA sequencing, 3 microarray applications, 4,5 cellular function studies, 6 and multiplexed bead-based assays. 7 The ability to identify multiple fluorescence emissions with high specificity is needed to gain sufficient multiplicity in biological analytical methods. Color decoding achieved by analyzing the detailed spectral characteristics of fluorophores can meet this demand, allowing fluorescence emissions with significant spectral overlap to be distinguished. 6, 8 -10 However, detection of multiple spectral signatures generally reduces measurement speed and throughput due to a larger volume of required information and suffers from the added complexity and cost of © 2010 American Chemical Society * To whom correspondence should be addressed. katsuo@umich.edu. SUPPORTING INFORMATION AVAILABLEAdditional information as noted in text. This material is available free of charge via the Internet at http://pubs.acs.org. Here, selective identification of multiple fluorescent molecular markers is also essential to discriminate diverse analyte species in the original sample mixture. However, a large hurdle against achieving high specificity and accuracy in multicolor flow cytometry arises when there are similarities and overlaps in the emission spectra of different dyes.14 For example, flow cytometers using as many as 11 fluorescent probe colors have been demonst...

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Section: Methodsmentioning

confidence: 99%

Section: Figuresmentioning

confidence: 99%

Multiplexed Spectral Signature Detection for Microfluidic Color-Coded Bioparticle Flow

et al. 2010

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“…Digital Object Identifier 10.1109/JQE.2010.2046721 [3], [6], [7]. Analog tuning is typically achieved via one of the following principles: electrostatic actuation of a structure held by flexures [3], [6], [8]- [10], piezo-electric [7], [11] or electrostatic stretching of a membrane [12], deformations of thermal actuators [13]- [15], electrostatic actuation for variable blaze angles [16], [17] or thermal/magnetic actuation of fiber Braggs gratings [18]. However, these tuning techniques trade the large actuation range of the digital actuation for analog precision.…”

Section: Introductionmentioning

confidence: 99%

Analog and Digital Deformable Diffractive Optics Actuated by Inter-Nanomagnet Forces

Deterre

Nichol

et al. 2010

IEEE J. Quantum Electron.

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In this paper, we present a novel actuation technique of diffractive optics based on magnetic interaction forces, permitting a fine resolution tuning as well as a tuning in discrete steps. This actuation combines advantages of "analog" and "digital" tuning in conventional diffractive optics. The application of a magnetic field perpendicularly to the beams of a freestanding grating coated with magnetic material generates intermagnet forces causing these beams to deform slightly or to clump together. A theoretical analysis of the forces has been carried out, followed by actuation simulations in both linear and nonlinear regimes for different types of gratings, showing examples of exponential and parabolic chirp profiles in addition to beam clumping. In experiment, the diffraction patterns of distinct fabricated gratings have shown both a continuous shift and smear as well as a discrete change in the diffracted angles proving the concept of analog and digital tuning.

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“…The first order grating efficiency for this feature is calculated to be 18%-23% for = 470-530 nm using GSOLVER software ͑Grating Solver Development Co., Allen, Texas͒. Our previous study 15 shows that the PDMS-silicon bond is strong enough to sustain stretching actuation at strain as large as 40% and that more than 100 million cycles of operation rea͒ …”

mentioning

confidence: 99%

“…13 The ML-SLLOG process involves ͑1͒ fabrication of comb drives on a silicon-on-insulator ͑SOI͒ wafer, ͑2͒ soft lithography 14 and lift-off of a three-dimensional PDMS microstructure, and ͑3͒ grafting of the PDMS microstructure onto the SOI patterns based on microassembly assisted by surface tension at an air-water interface. 15 The surfaces of the PDMS and silicon structures are both activated by oxygen plasma treatment to promote their permanent bonding in step ͑3͒.…”

mentioning

confidence: 99%

High-speed tuning of visible laser wavelength using a nanoimprinted grating optical tunable filter

Huang

Truxal

Tung

et al. 2009

Applied Physics Letters

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We report on a microelectromechanical tunable optical filter incorporating strain-tunable nanoimprinted elastomeric grating with a pitch varied by 18%. This device enables tuning of optical fiber-guided laser wavelength between = 473 and 532 nm within 0.5 ms by mechanically modulating the pitch with a silicon microactuator. We also demonstrate the use of the device for obtaining two-color images of live/dead-stained cells with the color intensity ratio varied by the actuator voltage applied. The small structure of the device integrated on a silicon chip may be used in portable systems for optical switching and spectroscopy. © 2009 American Institute of Physics. ͓doi:10.1063/1.3267083͔Laser wavelength tuning is an important operation for many optical instruments. It finds a wide variety of applications in fiber optical communication, 1,2 spectroscopy, 3,4 and photochemistry. 5 With recent advancements of multicolor fluorescence labeling techniques for biological studies, 6,7 a demand for the ability to tune laser wavelength in the visible band grows even stronger. In fluorescence spectroscopy and imaging, laser wavelength tuning is often achieved using tunable optical filters, such as acousto-optical tunable filters and liquid crystal tunable filters. 8 However, the relatively large-volume structures of these filters make them undesirable for the use in optofluidic lab-on-a-chip settings and point-of-care portable module systems.Several miniaturized silicon microelectromechanical systems ͑MEMS͒-based tunable gratings have been developed and demonstrated for high-speed wavelength tuning in the infrared band or in the visible band at reduced spectral resolution. [9][10][11] Toward the goal of MEMS-based highresolution visible wavelength tuning, our previous study 12 developed a nanoimprinted polydimethylsiloxane ͑PDMS͒ elastic pitch-variable grating mechanically tuned by on-chip silicon comb drive electrostatic actuators. But the device's small pitch variation range of 2.5% resulting in narrow bandwidth tuning ͑15 nm at = 558 nm͒ limits its practical use for biofluorescent applications that involve significant spectral shifts of light.In this letter, we demonstrate high-speed two-color laser switching using a polymer-on-silicon MEMS grating optical tunable filter ͑GOTF͒ device with a much larger pitch variation range. The GOTF device is fabricated using a method named the multilevel soft lithographic lift-off and grafting ͑ML-SLLOG͒. 13 The ML-SLLOG process involves ͑1͒ fabrication of comb drives on a silicon-on-insulator ͑SOI͒ wafer, ͑2͒ soft lithography 14 and lift-off of a three-dimensional PDMS microstructure, and ͑3͒ grafting of the PDMS microstructure onto the SOI patterns based on microassembly assisted by surface tension at an air-water interface. 15 The surfaces of the PDMS and silicon structures are both activated by oxygen plasma treatment to promote their permanent bonding in step ͑3͒. Figures 1͑a͒ and 1͑b͒ show the SEM and optical images of device͑s͒. Each GOTF device occupies a 3 mmϫ 3 mm area. The 25...

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A Flexible Nanograting Integrated Onto Silicon Micromachines by Soft Lithographic Replica Molding and Assembly

Cited by 11 publications

References 33 publications

Multiplexed Spectral Signature Detection for Microfluidic Color-Coded Bioparticle Flow

Multiplexed Spectral Signature Detection for Microfluidic Color-Coded Bioparticle Flow

Analog and Digital Deformable Diffractive Optics Actuated by Inter-Nanomagnet Forces

High-speed tuning of visible laser wavelength using a nanoimprinted grating optical tunable filter

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