title: Enhanced light collection in fluorescence microscopy using self-assembled micro-reflectors.
abstract: In fluorescence microscopy, the signal-to-noise ratio (SNR) of the optical system is directly linked to the numerical aperture (NA) of the microscope objective, which creates detection challenges for low-NA, wide-field and high-throughput imaging systems. Here we demonstrate a method to increase the light collection efficiency from micron-scale fluorescent objects using self-assembled vapor-condensed polyethylene glycol droplets, which act as micro-reflectors for fluorescent light. Around each fluorescent particle, a liquid meniscus is formed that increases the excitation efficiency and redirects part of the laterally-emitted fluorescent light towards the detector due to internal reflections at the liquid-air interface of the meniscus. The three-dimensional shape of this micro-reflector can be tuned as a function of time, vapor temperature, and substrate contact angle, providing us optimized SNR performance for fluorescent detection. Based on these self-assembled micro-reflectors, we experimentally demonstrate ~2.5-3 fold enhancement of the fluorescent signal from 2-10 μm sized particles. A theoretical explanation of the formation rate and shapes of these micro-reflectors is presented, along with a ray tracing model of their optical performance. This method can be used as a sample preparation technique for consumer electronics-based microscopy and sensing tools, thus increasing the sensitivity of low-NA systems that image fluorescent micro-objects.
authors.affiliation: Department of Electrical Engineering, University of California Los Angeles (UCLA), CA 90095, USA.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Göröcs
authors.affiliation: Department of Electrical Engineering, University of California Los Angeles (UCLA), CA 90095, USA.
authors.forename: Euan
authors.initials: E
authors.lastname: McLeod
authors.affiliation: 1] Department of Electrical Engineering, University of California Los Angeles (UCLA), CA 90095, USA [2] Department of Bioengineering, University of California Los Angeles (UCLA), CA 90095, USA [3] California NanoSystems Institute (CNSI), University of California Los Angeles (UCLA), CA 90095, USA.
authors.forename: Aydogan
authors.initials: A
authors.lastname: Ozcan
mesh_terms: D008856:Microscopy, Fluorescence / Q000295:instrumentation / Q000379:methods; D008962:Models, Theoretical; D011092:Polyethylene Glycols / Q000737:chemistry*
chemical_list: D011092:Polyethylene Glycols; C000595209:polyethylene glycol 1000