Optical imaging techniques in microfluidics and their applications

Abstract

Microfluidic devices have undergone rapid development in recent years and provide a lab-on-a-chip solution for many biomedical and chemical applications. Optical imaging techniques are essential in microfluidics for observing and extracting information from biological or chemical samples. Traditionally, imaging in microfluidics is achieved by bench-top conventional microscopes or other bulky imaging systems. More recently, many novel compact microscopic techniques have been developed to provide a low-cost and portable solution. In this review, we provide an overview of optical imaging techniques used in microfluidics followed with their applications. We first discuss bulky imaging systems including microscopes and interferometer-based techniques, then we focus on compact imaging systems that can be better integrated with microfluidic devices, including digital inline holography and scanning-based imaging techniques. The applications in biomedicine or chemistry are also discussed along with the specific imaging techniques.

Optical Imaging Approaches to Monitor Static and Dynamic Cell‐on‐Chip Platforms: A Tutorial Review

“…The other challenge is the low working distance between the objective lens and the sample surface. In an inverted microscope version, the magnifying arm is below the sample platform and that makes wide Small 2019, 15,1900737 Figure 2. Four imaging classes discussed in this review paper include: scattering-based imaging for static platforms, emission-based imaging for static platforms, scattering-based imaging for dynamic platforms, and emission-based imaging for dynamic platforms.…”

“…Rotation of the specimen by 180° could change hills to valleys and vice versa. It should be mentioned that carriers of the specimen such as plastic platforms may Small 2019, 15,1900737 not preserve the polarization and is not suitable for imaging with this microscope. As a conventional method, the DIC micro scopy is widely used for bioimaging.…”

“…There are several valuable review articles that cover the topic of static-cell imaging [2,[9][10][11][12][13][14] and dynamic-cell imaging [15][16][17][18][19][20] however, the aim of this tutorial review is to provide an intuitive understanding of optical imaging techniques that can be applied in monitoring static and dynamic cell-on-chip platforms. This paper is structured as follows.…”

Enhancing depth of focus in tilted microfluidics channels by digital holography

“…Although significant development in imaging technologies has occurred in recent years with impressive results [3][4][5][6], the novel 3D microfluidic paradigm poses ever more demanding expectations to face all the problems connected with the limited depth of focus in microscopy. In fact, the complex geometries of 3D microfluidic channels can become an insurmountable barrier in the analysis of micro-objects flowing along 3D paths, and limited depth of field (DOF) remains one of the main shortfalls in these optical imaging systems, especially in microscopy.…”

An Optofluidic Lens Array Microchip for High Resolution Stereo Microscopy

“…Research efforts towards low cost, compact imaging systems have focused on utilizing microlenses [7][8][9][10] and microlens arrays [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] optofluidic microscope [27,28] or even tomographic imaging methods [29,30]. Although these approaches demonstrated high-resolution imaging, they typically lack the flexibility and versatility of a stereo microscope where the user can easily adjust the focus and magnification or the illumination conditions depending on the sample that is being imaged.…”