The photonic microchip (IMB-CNM/CSIC).Many applications in the future, such as point of care testing or pollutant detection in water of food products, will be based on single-use microchips. Nevertheless, until now, most of these microchips still need peripherals that hamper their portability and their applicability in poor-resource environments.
The team led by Andreu Llobera, a CSIC's research associate Professor at the Institute of Microelectronics of Barcelona (IMB-CNM), has created a photonic microchip that includes a light source aligned with a microfluidic system. It enables real-time analysis of small-volume samples with high sensitivity. The work has been published in the Light: Science & Applications magazine, of Nature press.
Non-complex fabrication
The principle of detection is based on the quantitative measure of color changes (colorimetry) of a very small sample (microliters) which is inserted into the chip. The main advantage is that for the first time the light source is integrated in the microchip, as well as a whole series of micro-optic components in order to provide the system with a very high sensitivity. Besides, the system has been functionalized with specific biomolecules that selectively react when the analyte of interest is present in the sample.
“The photonic microchip merges all the know-how developed by our group in the last 10 years, and it means a huge step compared to the state of the art. Being so advanced, it could be thought that it is quite complex to fabricate. This is definitely not the case, since one of the main premises during its development was that it could be obtained with mass-production technologies, such as those used for CDs or DVDs” explains Andreu Llobera.
As the scientists have shown in the work published in the Light: Science & Applications magazine, the prototype can enzimatically detect hydrogen peroxide and food colorants, which are harmful at high concentrations. The prototype has been also tested for the detection of triglycerides, glucose and lactate.
Adapting the design
Once validated the photonic microchip concept, the next objective of the research team is to expand its range of applications. This can be done by tailoring the light source and fabricating it with a light emitting molecule that injects light into the system at the highest absortion wavelength of the analyte to be detected. Given the high flexibility and robustness of the photonic microchip, “we are open”, says Andreu Llobera, “to study the possibility of adapting our design to specific applications”.
It has been succesfully tested for detecting hydrogen peroxide, food colorants, triglycerides, glucose and lactate
This development improves the architecture of a device created by the same group three years ago. Then, they developed a photonic microchip that enabled portable devices for screening particles or cells in fluids. That device had an external light source that was coupled through an optical fiber to the microchip input. To correctly align and focus the light, the device included an innovative design with air mirrors to redirect the light to the sample.
The microchip was produced in one single step, reducing therefore the costs. Nevertheless, a high alignment accuracy was required to place the optical fibers. “It was necessary to place and align the light source very accurately. Only a misalignment of some thousandths of a millimetre dramatically lowered the microchip’s performance. “Soon it became clear that the next step in the photonic microchip development was to get the light source fully integrated”.
Multiplexed mode
Now, the alignment between the microfluidic zone and the light source is of high quality, since the latter is fabricated simultaneously with the micochip. The light source itself is a large improvement since, as opposed to the current state of art, it is conceptually very simple and based on a polymeric structure that entraps a fluorophore. “The fluorophore re-emits light towards the microfluidic zone by firstly absorbing part of the external light, which can be originated from a light-bulb or torch and can reach the microchip from any point or any angle. Therefore it is possible to make accurate measures without a complex equipment. The whole microchip is as big as a matchbox”, points out Llobera.
Another advantage is that these microchips can be produced in multiplexed mode. That means that, in the device, instead of having a single microchip, it is possible to have several of them working in parallel, which increases the reliability of the result-reducing the number of false positives-. Also, this would enable the simultaneous detection of several analytes.