Lensless Digital in-Line Holographic Microscopy for Space Biotechnology Applications

Abstract

Biomechanical changes at cellular level can dramatically affect living organisms in both aviation and space applications. Weightlessness induces morphological alteration of cells, which leads to tissue loss. Therefore, scientists have been studying the effect of weightlessness using cell culture based biological experiments using conventional microscopes. However, strict requirements regarding cost, weight and functionality limit the use of conventional microscopes in space environment. Lensless digital in-line holographic microscopy enables to use low-weight, low-cost and robust elements, such as a light emitting diode (LED), an aperture and an imaging sensor, instead of bulky, expensive and fragile optical elements, such as lenses, mirrors and filters. This technology offers a high field of view compared to conventional microscopes without affecting the resolution and it is also suitable for remote sensing applications with automated imaging capabilities. Here, we present a portable digital in-line holographic microscopy platform that allows to visualize cells and to analyze their viability in a microfluidic chip. The platform offers microscopic imaging with 1.55 μm spatial resolution, 21.7 mm 2 field of view and image coloring capability. This platform could potentially play an important role in space biotechnology applications by enabling low-cost, high-resolution and portable monitoring of cells.

Cell Separation with Hybrid Magnetic Levitation-Based Lensless Holographic Microscopy Platform

“…Recorded holograms on the imaging sensor (Fig. 2a) were subjected to a reconstruction process, which uses back-propagation with a spatial transfer function for obtaining real object images [8] as follows:…”

“…Traditional microscopes are bulky, composed of expensive and precise optics such as lenses, mirrors and filters to achieve highresolution images which make the image quality dramatically dependent upon configuration of instrument and skills of operating personnel. On the other hand, lensless digital inline holographic microscopy (LDIHM) eliminates costly and fragile optics by replacing simple illumination and recording scheme, which provides low-cost, high-resolution and portable microscopic imaging [8,9]. Furthermore, recorded images in LDIHM can be analyzed using fully automated digital image processing algorithms, which eliminates also human errors.…”

Density-Based Separation of Microparticles Using Magnetic Levitation Technology Integrated on Lensless Holographic Microscopy Platform

“…Captured holograms by CMOS imaging sensor are digitally back-propagated to retrieve the real image along the z-axis. Holograms are converted into real images by applying Angular Spectrum Method as follows [15]:…”

“…Therefore, entire active area of the imaging sensor can be used directly to achieve large field of view (>10 mm 2 ), which is 50 times greater than that of a conventional microscope equipped with 40× objective. Spatial resolution of 1.55 µm can be easily obtained in LDIHM, which is good enough for imaging few micron-sized particles [15].…”