Lensfree holographic imaging for on-chip cytometry and diagnostics

Abstract

We experimentally illustrate a lensfree holographic imaging platform to perform on-chip cytometry. By controlling the spatial coherence of the illumination source, we record a 2D holographic diffraction pattern of each cell or micro-particle on a chip using a high resolution sensor array that has ~2 µm pixel size. The recorded holographic image is then processed by using a custom developed decision algorithm for matching the detected hologram texture to existing library images for on-chip characterization and counting of a heterogeneous solution of interest. The holographic diffraction signature of any microscopic object is significantly different from the classical diffraction pattern of the same object. It improves the signal to noise ratio and the signature uniformity of the cell patterns; and also exhibits much better sensitivity for on-chip imaging of weakly scattering phase objects such as small bacteria or cells. We verify significantly improved performance of this holographic on-chip cytometry approach by automatically characterizing heterogeneous solutions of red blood cells, yeast cells, E. coli and various sized micro-particles without the use of any lenses or microscope objectives. This lensless on-chip holography platform will especially be useful for point-of-care cytometry and diagnostics applications involving e.g., infectious diseases such as HIV or malaria.

Label-free super-resolution imaging of adenoviruses by submerged microsphere optical nanoscopy

“…This nano-jet super-resolution focusing phenomenon has been applied for laser nano-fabrication. [22][23][24] By reversing this optical path, super-resolution imaging can be realized. The microsphere re-collects the light scattered by the virus/cells and converts the high spatialfrequency evanescent waves (no diffraction limits) into propagating waves that can be collected by far-field imaging.…”

“…Holographic imaging is another technique that has been reported to be able to image biological materials, such as bacteria. 24,26 Holographic imaging does not directly observe objects. Instead, it relies on the detection and digital processing of diffraction patterns when the object is illuminated.…”

Lensfree on-chip imaging using nanostructured surfaces

“…[1][2][3][4]6,7 Recent results confirmed the promising potential of lensfree in-line holography especially for high-throughput cytometry applications. 6 Quite recently, lensfree on-chip imaging has also been extended to fluorescence microscopy to achieve an ultrawide imaging field-of-view ͑FOV͒ of Ͼ8 cm 2 without the use of any lenses or mechanical scanning. 8 Despite its limited resolution, such a wide-field fluorescent on-chip imaging modality, when combined with in-line digital holography could especially be significant for high-throughput diagnostic applications using large area microfluidic devices.…”

“…[1][2][3][4][5][6][7][8] Such on-chip microscope designs would especially benefit microfluidic systems to create powerful capabilities especially for medical diagnostics and cytometry applications. Being light-weight and compact, lensfree imaging can also potentially create an important alternative to conventional lens-based microscopy especially for telemedicine applications.…”

Sub-pixel resolving optofluidic microscope for on-chip cell imaging

“…[1][2][3][4][5][6][7][8][9][10][11][12] Compact, inexpensive and portable imaging systems can fulfill many needs in biological research, point-of-care analysis and field diagnostics. For example, an on-chip microscope, produced at scale at existing semiconductor foundries and capable of imaging blood cell or parasite morphology in high resolution, would bring affordable healthcare diagnostics to less developed populations in rural settings, where it is too costly to deploy expensive conventional microscopes and skilled technicians.…”