A research team at Chalmers University of Technology, Sweden, has developed new laser technology that could lead to tiny, cost-effective biosensors. The sensors integrate lasers and optics together on a centimeter-sized chip, which could move testing from hospitals to patients' homes. This, in turn, would free up hospital beds and reduce visits to clinics.

By studying how various biomolecules interact with each other - for example antibodies in the immune system and xenobiotic antigens - researchers can gain valuable insights leading to new medicines and vaccines or assess whether a sample contains signs of infection.

Optical biosensors based on a technique called surface-plasmon resonance are an important tool used for studying these types of interactions. The sensors direct light onto a gold surface and measure minuscule changes in the light’s reflection when biomolecules are placed on the surface.
Now, a research team at Chalmers is announcing a new laser technology that makes it possible to create such biosensors in a miniature format. The laser source and the necessary optics are directly integrated onto a semiconductor chip, allowing for significantly more compact sensors. This opens the door to making optical sensing technology portable and applicable outside the laboratory environment.

“With this technology, we want to create an instrument that allows healthcare professionals to take certain samples in the patient’s home. For example, we’re currently evaluating how well our sensor can perform a C-reactive protein (CRP) test. Because this technology is very general and can detect a wide range of biomolecular interactions, we see many potential applications for a wide variety of tests. This could allow patients to be discharged from hospital sooner after an operation – thereby freeing up hospital beds – and reduce the number of healthcare visits for sampling,” says Erik Strandberg, doctoral candidate in photonics at Chalmers and lead author of a study published in ACS Sensors.

The whole solution, packaged on a tiny chip

To be able to monitor the interaction of biomolecules using an optical sensor, a precise laser beam must strike the gold surface at a very steep angle. The solutions used today require bulky optical components, such as prisms, which also make them time-consuming to install and align. The Chalmers team’s sensor consists of a one-centimetre chip fitted with hundreds of microscopic lasers, where the controlling optics to form exactly the right beam is integrated directly into the chip. This allows for a much smaller and lighter light source, which enables the creation of a compact sensor so small that it fits in the palm of your hand.
“By successfully integrating the optics with the laser sources right on the chip, our innovation opens a lot of doors and is a key step towards shrinking the current biotech instruments and creating portable, battery-powered systems. The chips we manufacture are about the size of a thumbtack and contain hundreds of lasers, each measuring 200x250 micrometres – few times thicker than a hair. Having both the laser and the optics integrated into the same semiconductor chip also enables cost-effective large-scale production of light sources for this technology,” Erik Strandberg says.

Aiming for healthcare settings

In the next step, the researchers aim to further develop the technology by boosting the sensitivity of the sensor, as well as increasing the number of samples that can be analysed simultaneously.

“So far, we haven’t been able to use all the lasers on our chips to analyse samples, but this field offers great opportunities for further development. If we succeed, we believe the sensor will eventually make it possible to analyse significantly more samples at once than current technologies allow. But first, we plan to create a prototype of a portable sensor that can be used without extensive training. The ultimate goal is for hospitals and clinics to be able to use the sensor outside the lab,” says Hana Jungová, senior researcher in the study.

More about the research
The team’s study, Flat Plasmonic Biosensor with an On-Chip Metagrating-Integrated Laser, was published in ACS Sensors. The article’s authors are Erik Strandberg, Mindaugas Juodėnas, Mikael Käll and Hana Jungová at Chalmers University of Technology. The study was funded by the Knut and Alice Wallenberg Foundation.