A nanotech sensor that turns molecular fingerprints into bar codes

June 7, 2018, Ecole Polytechnique Federale de Lausanne
The authors show a pixelated sensor metasurface for molecular spectroscopy. It consists of metapixels designed to concentrate light into nanometer-sized volumes in order to amplify and detect the absorption fingerprint of analyte molecules at specific resonance wavelengths. Simultaneous imaging-based read-out of all metapixels provides a spatial map of the molecular absorption fingerprint sampled at the individual resonance wavelengths. This pixelated absorption map can be seen as a two-dimensional barcode of the molecular fingerprint, which encodes the characteristic absorption bands as distinct features of the resulting image. Credit: EPFL

Infrared spectroscopy is the benchmark method for detecting and analyzing organic compounds. But it requires complicated procedures and large, expensive instruments, making device miniaturization challenging and hindering its use for some industrial and medical applications and for data collection out in the field, such as for measuring pollutant concentrations. Furthermore, it is fundamentally limited by low sensitivities and therefore requires large sample amounts.

However, scientists at EPFL's School of Engineering and at Australian National University (ANU) have developed a compact and sensitive nanophotonic system that can identify a molecule's absorption characteristics without using conventional spectrometry.

Their system consists of an engineered surface covered with hundreds of tiny sensors called metapixels, which can generate a distinct bar code for every molecule that the surface comes into contact with. These bar codes can be massively analyzed and classified using advanced pattern recognition and sorting technology such as . This research—which sits at the crossroads of physics, nanotechnology and big data—has been published in Science.

Translating molecules into bar codes

The chemical bonds in organic molecules each have a specific orientation and vibrational mode. That means every molecule has a set of characteristic energy levels, which are commonly located in the mid-infrared range—corresponding to wavelengths of around 4 to 10 microns. Therefore, each type of molecule absorbs light at different frequencies, giving each one a unique "signature." Infrared spectroscopy detects whether a given molecule is present in a sample by seeing if the sample absorbs light rays at the molecule's signature frequencies. However, such analyses require lab instruments with a hefty size and price tag.

The pioneering system developed by the EPFL scientists is both highly sensitive and capable of being miniaturized; it uses nanostructures that can trap light on the nanoscale and thereby provide very high detection levels for samples on the surface. "The we want to detect are nanometric in scale, so bridging this size gap is an essential step," says Hatice Altug, head of EPFL's BioNanoPhotonic Systems Laboratory and a coauthor of the study.

The system's nanostructures are grouped into what are called metapixels so that each one resonates at a different frequency. When a molecule comes into contact with the surface, the way the molecule absorbs light changes the behavior of all the metapixels it touches.

"Importantly, the metapixels are arranged in such a way that different vibrational frequencies are mapped to different areas on the surface," says Andreas Tittl, lead author of the study.

This creates a pixelated map of light absorption that can be translated into a molecular bar —all without using a spectrometer.

The scientists have already used their system to detect polymers, pesticides and . What's more, their system is compatible with CMOS technology.

"Thanks to our sensors' unique optical properties, we can generate bar codes even with broadband light sources and detectors," says Aleksandrs Leitis, a coauthor of the study.

There are a number of potential applications for this new system. "For instance, it could be used to make portable medical testing devices that generate bar codes for each of the biomarkers found in a blood sample," says Dragomir Neshev, another coauthor of the study.

Artificial intelligence could be used in conjunction with this new technology to create and process a whole library of molecular bar codes for compounds ranging from protein and DNA to pesticides and polymers. That would give researchers a new tool for quickly and accurately spotting miniscule amounts of compounds present in complex samples.

Explore further: Phononic SEIRA—enhancing light-molecule interactions via crystal lattice vibrations

More information: "Imaging-based molecular barcoding with pixelated dielectric metasurfaces" Science (2018). science.sciencemag.org/cgi/doi … 1126/science.aas9768

Related Stories

Combing light for tell-tale chemical fingerprints

May 23, 2018

A laser-based technique that can scan and lock on to molecular vibrational signals that are normally too complex to resolve clearly could enable production of sensors for multi-species identification in harsh environments, ...

Recommended for you

Engineers repurpose wasp venom as an antibiotic drug

December 7, 2018

The venom of insects such as wasps and bees is full of compounds that can kill bacteria. Unfortunately, many of these compounds are also toxic for humans, making it impossible to use them as antibiotic drugs.

Researchers probe hydrogen bonds using new technique

December 7, 2018

Researchers at Carnegie Mellon University have used nuclear resonance vibrational spectroscopy to probe the hydrogen bonds that modulate the chemical reactivity of enzymes, catalysts and biomimetic complexes. The technique ...

Are amorphous solids elastic or plastic?

December 7, 2018

In a crystalline solid, the atoms form an ordered lattice. Crystalline solids respond elastically to small deformations: When the applied strain is removed, the macroscopic stress, as well as the microscopic configuration ...

Molecular insights into spider silk

December 7, 2018

Spider silk is one of the toughest fibres in nature and has astounding properties. Scientists from the University of Würzburg discovered new molecular details of self-assembly of a spider silk fibre protein.

Copycat cells command new powers of communication

December 7, 2018

From kryptonite for Superman to plant toxins for poison ivy, chemical reactions within the body's cells can be transformative. And, when it comes to transmuting cells, UC San Diego researchers are becoming superhero-like ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.