Lensless, reflection-based dark-field microscopy (RDFM) on a CMOS chip

Abstract

We present for the first time a lens-free, oblique illumination imaging platform for on-sensor dark- field microscopy and shadow-based 3D object measurements. It consists of an LED point source that illuminates a 5-megapixel, 1.4 µm pixel size, back-illuminated CMOS sensor at angles between 0° and 90°. Analytes (polystyrene beads, microorganisms, and cells) were placed and imaged directly onto the sensor. The spatial resolution of this imaging system is limited by the pixel size (∼1.4 µm) over the whole area of the sensor (3.6×2.73 mm). We demonstrated two imaging modalities: (i) shadow imaging for estimation of 3D object dimensions (on polystyrene beads and microorganisms) when the illumination angle is between 0° and 85°, and (ii) dark-field imaging, at >85° illumination angles. In dark-field mode, a 3-4 times drop in background intensity and contrast reversal similar to traditional dark-field imaging was observed, due to larger reflection intensities at those angles. With this modality, we were able to detect and analyze morphological features of bacteria and single-celled algae clusters.

Complementary Metal-Oxide-Semiconductor-Based Sensing Platform for Trapping, Imaging, and Chemical Characterization of Biological Samples

“…58 Finally, attempts to combine SERS and optical microscopy in one platform have been reported previously, mostly by utilizing research-grade microscopes, which operate on a tradeoff mode between spatial resolution and field of view. 9 One recent example is of simultaneous SERS measurements and stochastic optical reconstruction microscopy (STORM) of biological structures and microorganisms, 59−61 which reports high spatial resolution (<50 nm) and chemical information on the analyte but is limited in terms of field of view. The technique is also complex, requires acquisition of multiple images, and uses computing-intensive image reconstruction algorithms.…”

“…While such approaches have been successfully applied for imaging of biological samples , and nanoparticles, they require the use of complex image reconstruction algorithms. However, direct on-chip imaging enables high-resolution microscopy with ease of image acquisition and does not require a complicated image reconstruction step. , Previously, our group reported a direct on-chip dark-field microscopy as a new modality in addition to conventional transmission-based imaging modality . Development of a new imaging mode to direct on-chip imaging platforms expands existing range of their functionality and opens new ways for their applications.…”

“…7,8 Previously, our group reported a direct on-chip dark-field microscopy as a new modality in addition to conventional transmission-based imaging modality. 9 Development of a new imaging mode to direct on-chip imaging platforms expands existing range of their functionality and opens new ways for their applications.…”

SE-ECL on CMOS: a miniaturized electrochemiluminescence biosensor

“…The field of view (FOV) of the device is 3.67 mm × 2.73 mm, which is the active area of the CMOS sensor, and the spatial resolution of the system is 1.4 μm, limited by the pixel size. 37 A 4-point probe (Lucaslabs, Signatone Pro4) and a profilometer (Bruker, DektakXT) were utilized to measure the sheet resistivity of ITO and the height of the microfluidic channel, respectively (Fig. 2A and B).…”