Publication

System for optical detection and imaging of sub-diffraction-limited nano-objects

Abstract

Nano-objects (8) with feature size smaller than the classical Abbe's diffraction limit can be optically detected via a microlens (4) array configured in a miniaturized microfluidic device. A hydrophilic microwell (3) array in a hydrophobic layer (2) is firstly fabricated by standard microfabrication processes. Dielectric microspheres (4) with high refractive index are used as microlenses and patterned inside the hydrophilic microwells (3) resulting in a microlens array format with high uniformity over a large surface area. These microlenses (4) focus the illuminating light into a region that is referred to as a photonic nanojet (6), which is characterized by a high optical intensity and sub-diffraction transverse dimension. The microlens array is integrated with a microfluidic channel (9), where a fluid medium (7) with nano-objects (8) is present. When the nano-objects (8) pass through the photonic nanojet (6), the retroreflected light from the microsphere-nano-object ensemble is highly enhanced and measured by an optical signal detection component (11) (conventional optical microscope, etc.), and the enhancement of the retroreflected light is very sensitive to the size of the nano-objects (8). Therefore, not only the existence of the nano-objects (8) can be qualitatively monitored, but also the size of these nano-objects can be quantitatively determined by the proposed technique.

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Related concepts (32)
Near-field scanning optical microscope
Near-field scanning optical microscopy (NSOM) or scanning near-field optical microscopy (SNOM) is a microscopy technique for nanostructure investigation that breaks the far field resolution limit by exploiting the properties of evanescent waves. In SNOM, the excitation laser light is focused through an aperture with a diameter smaller than the excitation wavelength, resulting in an evanescent field (or near-field) on the far side of the aperture.
Microfluidics
Microfluidics refers to a system that manipulates a small amount of fluids ((10−9 to 10−18 liters) using small channels with sizes ten to hundreds micrometres. It is a multidisciplinary field that involves molecular analysis, biodefence, molecular biology, and microelectronics. It has practical applications in the design of systems that process low volumes of fluids to achieve multiplexing, automation, and high-throughput screening.
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