We've created a device that could allow instant disease diagnosis – while fitting inside your phone lens

Infectious diseases such as malaria remain a leading cause of death in many regions. This is partly because people there don’t have access to medical diagnostic tools that can detect these diseases (along with a range of non-infectious diseases) at an early stage, when there is more scope for treatment.

It’s a challenge scientists have risen to, with a goal to democratise health care for economically disadvantaged people the world over.

My colleagues and I have developed a new method for the investigation of biological cells which is small enough to fit into a smartphone lens.

While we have so far only tested it in the lab, we hope in the future this nanotechnology could enable disease detection in real-world medical settings using just a mobile device. We hope our work can eventually help save millions of lives.

Read more: World's first mass malaria vaccine rollout could prevent thousands of children dying

How to investigate a biological cell

Being able to investigate biological cells through optical microscopes is a fundamental part of medical diagnostics.

This is because specific changes in cells that can be observed under a microscope are often indicative of diseases. In the case of malaria, for example, the gold-standard method of detection involves using microscope images to identify specific changes in a patient’s red blood cells.

But biological cells are good at hiding. Many of their internal features are practically transparent and almost invisible to conventional microscopes. To make these features visible, we need to apply tricks.

One way is to introduce some sort of chemical staining, which adds contrast to the transparent features of cells.

Other approaches use a process called “phase imaging”. Phase imaging exploits the fact that light, which has passed through the cell, contains information about the transparent parts of the cell – and makes this information visible to the human eye.

Conventional phase-imaging methods rely on a range of bulky components such as prisms and interference setups, which cost thousands of dollars. Also, expensive and bulky equipment can’t be easily made available in remote regions and economically disadvantaged countries.

Enter nanotechnology

A major scientific effort is currently directed towards leveraging nanotechnology to replace traditional large optical components.

This is being done by creating nanometer-thick devices with the potential for low-cost mass production. These devices could be integrated into mobile devices, such as smartphone cameras, in the future.

In the specific case of phase imaging, scientists have previously only been able to develop systems that:

• are reliant on time-consuming computational post processing, which makes the process more complex, and doesn’t allow for real-time imaging

• still use mechanically moving or rotating parts. Because of the space requirements of these parts, they are incompatible with completely flat optical components and ultra-compact integration.

We have developed a device that can perform instantaneous phase-imaging without these limitations. Our solution is only a few hundred nanometers thick, and could be integrated into camera lenses, in the form of a flat film on top of the lens.

How we did it

We inscribed a nanostructure into a very thin film (less than 200 nanometres thick) which enables phase imaging using an effect sometimes referred to as “optical spin-orbit coupling”.

The principle of operation is simple. A transparent object, such as a biological cell, is placed on top of the device. Light is shone through the cell and the previously invisible structure of the cell becomes visible on the other side.