Two-dimensional microlens array for low-cost high-resolution bio-imaging

Abstract

Mobile microscopes, which are cost-effective and field-portable, are rapidly gaining popularity for a variety of different applications, including disease diagnostics. Different imaging modalities, based on transmission, absorption, scattering, phase change, and fluorescence have been developed, depending on the specific application. Mobile microscopes are typically designed to have single magnification, and the maximum achievable resolution is limited by the numerical aperture (N.A.) of the objective lens, due to diffraction of light. Here we present a low-cost imaging substrate containing a two-dimensional (2D) microlens array that enables multi-modal imaging (phase-contrast, dark-field, and fluorescence) with resolution beyond the diffraction limit. The substrate is placed in contact with the sample to form a sandwich structure and the image magnification is attributed to the formation of virtual images by the individual microspheres. This reusable substrate can be easily attached to and detached from the sample, with minimal to no sample damage. A variety of different sizes of glass microspheres (40- 500 𝜇m) were explored and their performance was characterized using fluorescent particles (200 nm – 1 μm). The substrate enabled imaging with sub-400nm resolution, using a low magnification objective lens with N.A.~0.25. Proof-of-concept experiments with this substrate were performed by imaging mammalian tissues, red blood cells, including sickle cells. This technique provides a low-cost, easy- to-use method of improving the resolution of multi-modal imaging systems, which is particularly useful for mobile microscopy applications.

Advances in Lensless Fluorescence Microscopy Design

“…LLMF has been used for various biological applications, including for imaging cells, tissues, and pathogens. Cell imaging is a cornerstone of biological and medical research, offering the real-time visualization of cellular processes like division, migration, and interaction to understand how cells function and respond to stimuli (e.g., drugs), as well as to diagnose diseases through the identification of morphological changes [58][59][60]. LLFM has been used to image different kinds of cells, such as the multicolor imaging of double-stained human breast cancer SK-BR-3, revealing detailed cellular structures such as membranes and nuclei [51].…”

Label-free identification of cell death mechanism using scattering-based microscopy and deep learning

“…Scattering signatures from tissues have previously been used for studying different properties, such as identifying cancerous regions [62][63][64], including its microscopic morphology [65]. Some of the commonly used scattering based imaging techniques include dark field microscopy, diffuse reflectance and sub-diffuse spatial frequency domain imaging amongst others [66][67][68][69][70][71][72][73]. While dark field microscopy enables detection of nanostructures down to 10 nm, other techniques that can offer similar sensitivity include interferometric scattering (iSCAT) microscopy, coherent brightfield (COBRI) microscopy, spatial light interference microscopy (SLIM), and interferometric reflectance imaging sensor (IRIS), amongst others [74].…”