Endowing a plain fluidic chip with micro-optics: a holographic microscope slide

Abstract

Lab-on-a-Chip (LoC) devices are extremely promising in that they enable diagnostic functions at the point-of-care. Within this scope, an important goal is to design imaging schemes that can be used out of the laboratory. In this paper, we introduce and test a pocket holographic slide that allows digital holography microscopy to be performed without an interferometer setup. Instead, a commercial off-the-shelf plastic chip is engineered and functionalized with this aim. The microfluidic chip is endowed with micro-optics, that is, a diffraction grating and polymeric lenses, to build an interferometer directly on the chip, avoiding the need for a reference arm and external bulky optical components. Thanks to the single-beam scheme, the system is completely integrated and robust against vibrations, sharing the useful features of any common path interferometer. Hence, it becomes possible to bring holographic functionalities out of the lab, moving complexity from the external optical apparatus to the chip itself. Label-free imaging and quantitative phase contrast mapping of live samples are demonstrated, along with flexible refocusing capabilities. Thus, a liquid volume can be analyzed in one single shot with no need for mechanical scanning systems.

Holotomography: refractive index as an intrinsic imaging contrast for 3-D label-free live cell imaging

“…From an application point of view, the utilization of microfluidic devices for 3-D RI tomography may open various opportunities. The use of a designed chip can be used to simplify an optical setup for the 3-D RI measurements (Bianco et al 2017), and to allow the quantification of chemical concentrations of fluids in a microfluidic channel ).…”

Microfluidic Based Optical Microscopes on Chip

“…( c ) Scheme of the device presented by Bianco et al 2017, where a diffracting grating is integrated in a commercially available microfluidic chip, which allows off‐axis digital holography by means of a single beam (reproduced from Ref. , with permission from Springer Nature). [Color figure can be viewed at wileyonlinelibrary.com]…”

Wide field of view common-path lateral-shearing digital holographic interference microscope

“…[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] Common-path techniques duplicate the object wavefront and generate the reference wavefront from one of these duplicated wavefronts. This can be done by either spatially filtering one of the duplicated wavefronts and using it as the reference wavefront [19][20][21][22][23][24][25][26][27][28][29] or using a portion of the duplicated wavefront (which does not contain object information) as the reference wavefront. [30][31][32][33][34][35][36][37][38] A second technique termed a self-referencing DHIM technique requires fewer optical elements and hence leads to very compact off-axis geometries.…”