Nanoimprinted polymer chips for light induced local heating of liquids in micro- and nanochannels

Publication: ResearchConference article – Annual report year: 2010

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A nanoimprinted polymer chip with a thin near-infrared absorber layer that enables light-induced local heating (LILH) of liquids inside micro- and nanochannels is presented. An infrared laser spot and corresponding hot-spot could be scanned across the device. Large temperature gradients yield thermophoretic forces, which are used to manipulate and stretch individual DNA molecules confined in nanochannels. The absorber layer consists of a commercially available phthalocyanine dye (Fujifilm), with a narrow absorption peak at approximately 775 nm, dissolved in SU-8 photoresist (Microchem Corp.). The 500 nm thick absorber layer is spin-coated on a transparent substrate and UV exposed. Microand nanofluidic channels are defined by nanoimprint lithography in a 1.5 μm thick layer of low molecular weight polymethyl methacrylate (PMMA, Microchem Corp.), which is spin coated on top of the absorber layer. We have used a previously developed two-level hybrid stamp for replicating two V-shaped microchannels (width=50 μm and height = 900 nm) bridged by an array of 200 nanochannels (width and height of 250 nm). The fluidic channels are finally sealed with a lid using PMMA to PMMA thermal bonding. Light from a 785 nm laser diode was focused from the backside of the chip to a spot diameter down to 5 ..m in the absorber layer, yielding a localized heating (Gaussian profile) and large temperature gradients in the liquid in the nanochannels. A laser power of 38 mW yielded a temperature of 40°C in the center of a 10 μm 1/e diameter. Flourescence microscopy was performed from the frontside.
Original languageEnglish
JournalProceedings of the SPIE - The International Society for Optical Engineering
Publication date2010
Volume7764
Pages77640I
ISSN0277-786X
DOIs
StatePublished

Conference

ConferenceNanoengineering: Fabrication, Properties, Optics, and Devices VII
CountryUnited States
CitySan Diego, CA
Period03/08/1004/08/10
CitationsWeb of Science® Times Cited: 0
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