Cost-effective and compact wide-field fluorescent imaging on a cell-phone

Abstract

We demonstrate wide-field fluorescent and darkfield imaging on a cell-phone with compact, lightweight and cost-effective optical components that are mechanically attached to the existing camera unit of the cell-phone. For this purpose, we used battery powered light-emitting diodes (LEDs) to pump the sample of interest from the side using butt-coupling, where the pump light was guided within the sample cuvette to uniformly excite the specimen. The fluorescent emission from the sample was then imaged using an additional lens that was positioned right in front of the existing lens of the cell-phone camera. Because the excitation occurs through guided waves that propagate perpendicular to our detection path, an inexpensive plastic colour filter was sufficient to create the dark-field background required for fluorescent imaging, without the need for a thin-film interference filter. We validate the performance of this platform by imaging various fluorescent micro-objects in 2 colours (i.e., red and green) over a large field-of-view (FOV) of ~81 mm 2 with a raw spatial resolution of ~20 μm. With additional digital processing of the captured cell-phone images, through the use of compressive sampling theory, we demonstrate ~2 fold improvement in our resolving power, achieving ~10 μm resolution without a trade-off in our FOV. Further, we also demonstrate darkfield imaging of non-fluorescent specimen using the same interface, where this time the scattered light from the objects is detected without the use of any filters. The capability of imaging a wide FOV would be exceedingly important to probe large sample volumes (e.g., >0.1 mL) of e.g., blood, urine, sputum or water, and for this end we also demonstrate fluorescent imaging of labeled white-blood cells from whole blood samples, as well as waterborne pathogenic protozoan parasites such as Giardia Lamblia cysts. Weighing only ~28 g (~1 ounce), this compact and cost-effective fluorescent imaging platform attached to a cell-phone could be quite useful especially for resource-limited settings, and might provide an important tool for wide-field imaging and quantification of various lab-on-a-chip assays developed for global health applications, such as monitoring of HIV+ patients for CD4 counts or viral load measurements.

Real time blood testing using quantitative phase imaging

“…Thus, novel light microscopy designs have resulted in miniaturized and inexpensive devices for cell imaging in low resource settings [4,5,6,7,8,9]. In particular, the combination of microscopy and microfluidics promises to commoditize imaging instruments and even convert them into disposable accessories [10].…”

Handheld high-throughput plasmonic biosensor using computational on-chip imaging

“…Similarly, various point-of-care diagnostic devices have been developed and among them optical imaging and sensing techniques are highly advantageous as they can provide real-time, highresolution and highly sensitive quantitative information, potentially assisting rapid and accurate diagnosis. [30][31][32][33][34][35][36][37][38][39][40] To date, a number of optical techniques have been proposed for point-of-care diagnostics such as in vitro optical devices, [41][42][43][44][45][46][47][48][49][50][51][52][53] including portable optical imaging systems, optical microscopes integrated to cell phones or in vivo optical devices, [54][55][56][57][58][59][60][61][62][63] involving confocal microscopy, microendoscopy and optical coherence tomography techniques. Among these approaches, lens-free computational on-chip imaging 64 has been an emerging technique that can eliminate the need for bulky and costly optical components while also preserving (or even enhancing in certain cases) the image resolution, field of view and sensitivity.…”

In vivoevaluation of battery-operated light-emitting diode-based photodynamic therapy efficacy using tumor volume and biomarker expression as endpoints

“…43 Often, fluorescence imaging of PpIX is used as a dosimetric parameter and the change in PpIX fluorescence post-therapy, i.e., the photobleaching of PpIX, has been useful in personalizing therapeutic dose and providing better insights into treatment efficacy. Along with low-cost light sources similar to the one described here, portable imaging systems, including potential smart phone based devices for fluorescence imaging techniques, [44][45][46][47][48] combined with strategies for more homogeneous PpIX synthesis might provide rapid and inexpensive options for therapy and monitoring design in LMICs.…”