20 Feb 2018
Technology providing 5 µm resolution imagery but requiring no external light source made freely downloadable by Australian developers.
Researchers from the ARC Centre of Excellence for Nanoscale BioPhotonics (CNBP) in Australia have developed a 3D printable ‘clip-on’ optical device that they say turns any smart phone into a fully functional microscope – with sufficiently powerful resolution for testing water quality or diagnosing malaria.
Anthony Orth and colleagues, who have just published their work in the journal Nature Scientific Reports, say that the simple system is powerful enough to visualize specimens just 5 µm across.
No external light source
Crucially, the design uses either sunlight or the phone’s integral camera flash light source, with no external illumination required.
“The clip-on technology is unique in that it requires no external power or light source to work yet offers high-powered microscopic performance in a robust and mobile handheld package,” they report.
The CNBP team has also made the technology freely available by sharing the 3D printing files needed to fabricate the clip-on device. Anybody interested in doing so can download the files here.
“Our 3D-printed device itself has the necessary geometry to create diffuse transmission illumination without employing an external diffusely reflective object behind the sample,” wrote the team in their paper.
They explain that, because the flash unit is offset from the phone’s camera and points in the same direction, reflection-mode and transmission-mode microscopy are not usually possible. But the geometry of the 3D-printed “clip” creates diffuse transmission illumination, while internal reflection within a sample’s glass slide enables dark-field imaging.
“As a result, we can observe samples that are nearly invisible under bright-field operation due to low absorption or refractive index contrast, such as cells in media,” reports the team.
Orth, a research fellow at Royal Melbourne Institute of Technology (RMIT University), believes that the technology will be ideal for use in remote areas, or for fieldwork where conventional microscopes impractical.
“We’ve designed a simple mobile phone microscope that takes advantage of the integrated illumination available with nearly all smart phone cameras,” he said.
The clip-on attachment has been engineered with internal illumination “tunnels”. They guide light from the camera’s flash to illuminate the sample from behind.
This overcomes issues seen with other microscope-converted phones, claims Orth. “Almost all other phone-based microscopes use externally powered light sources while there’s a perfectly good flash on the phone itself,” he adds.
“External LEDs and power sources can make these other systems surprisingly complex, bulky and difficult to assemble.”
It means that the microscope can be used after one simple assembly step, with no need for additional illumination optics.
“The added dark-field functionality lets us observe samples that are nearly invisible under conventional bright-field operation such as cells in media,” Orth points out.
“Having both capabilities in such a small device is extremely beneficial and increases the range of activity that the microscope can be successfully used for.”
He sees applications in monitoring water quality, blood samples, environmental observation, and early disease detection and diagnosis – with particular utility in the developing world.
“Powerful microscopes can be few and far between in some regions,” he says. “They’re often only found in larger population centers and not in remote or smaller communities. Yet their use in these areas can be essential - for determining water quality for drinking, through to analyzing blood samples for parasites, or for disease diagnosis including malaria.”
The phone microscope has already been tested by Orth and his CNBP colleagues in a number of applications, viewing samples including unlabelled cell nuclei, zooplankton and live cattle semen, in support of livestock fertility testing.