The analysis of potable water supplies for the presence of microorganisms can be a time-, labor- and technology-intensive task. To simplify this process — particularly for developing areas where expertise and equipment are in short supply — a lensless fluorescence detection system was developed to provide highly sensitive detection of deadly microorganisms in drinking water.

The new approach devised by researchers from Phutung Research Institute (Nepal), University of York (U.K.) and University of São Paulo (Brazil) is intended to offer a low-cost, simplified means to monitor water quality in resource-limited settings. The researchers determined that while optical lenses are commonly used in devices such as cameras and microscopes, these optical components often reduce performance for practical situations that don’t require images.

“Our analysis revealed that using a light source, detectors and sample sizes that are all as large and as close to each other as possible produces a stronger signal, leading to better performance for water quality,” they explained.

The lensless fluorescence system was engineered using large 1 mm x 1 mm LEDs and detectors and relies on UV light to excite proteins from harmful microbes and subsequently detect the resulting fluorescence with a 2.4 mm x 2.4 mm photodiode. The system described in Optica was demonstrated to generate a fluorescence signal that is about double the strength of a lensed system. The lensless technology overcomes the limitations posed by the need to use larger sources and detectors, and the finite imaging distance required between the components and sample in lensed instruments.

During laboratory evaluations, the device proved capable of detecting waterborne bacterial proteins down to levels of less than 1 ppb, which meets World Health Organization’s standards for detecting fecal contamination in drinking water. A portable version of the lensless fluorometer is now being advanced for field testing.

To contact the author of this article, email shimmelstein@globalspec.com