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.

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

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 artificial neural networks. 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 molecules 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 code – all without using a spectrometer.

The scientists have already used their system to detect polymers, pesticides and organic compounds. 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.

Researchers at Seoul National University and Stanford University developed artificial mechanosensory nerves using flexible organic devices to emulate biological sensory afferent nerves. They used the artificial mechanosensory nerves to control a disabled insect leg and distinguish braille characters.

Compared to conventional digital computers, biological nervous system is powerful for real-world problems, such as visual image processing, voice recognition, tactile sensing, and movement control. This inspired scientists and engineers to work on neuromorphic computing, bioinspired sensors, robot control, and prosthetics. The previous approaches involved implementations at the software level on conventional digital computers and circuit designs using classical silicon devices which have shown critical issues related to power consumption, cost, and multifunction.

The research describes artificial mechanosensory nerves based on flexible organic devices to emulate biological mechanosensory nerves. “The recently found mechanisms of information processing in biological mechanosensory nerves were adopted in our artificial system,” said Zhenan Bao at Stanford University.

The artificial mechanosensory nerves are composed of three essential components: mechanoreceptors (resistive pressure sensors), neurons (organic ring oscillators), and synapses (organic electrochemical transistors). The pressure information from artificial mechanoreceptors can be converted to action potentials through artificial neurons. Multiple action potentials can be integrated into an artificial synapse to actuate biological muscles and recognize braille characters.

Devices that mimic the signal processing and functionality of biological systems can simplify the design of bioinspired system or reduce power consumption. The researchers said organic devices are advantageous because their functional properties can be tuned, they can be printed on a large area at a low cost, and they are flexible like soft biological systems.

Wentao Xu, a researcher at Seoul National University, and Yeongin Kim and Alex Chortos, graduate students at Stanford University, used their artificial mechanosensory nerves to detect large-scale textures and object movements and distinguish braille characters. They also connected the artificial mechanosensory nerves to motor nerves in a detached insect leg and control muscles.

Professor Tae-Woo Lee, a Professor at Seoul National University said, “Our artificial mechanosensory nerves can be used for bioinspired robots and prosthetics compatible with and comfortable for humans.” Lee said, “The development of human-like robots and prosthetics that help people with neurological disabilities can benefit from our work.”

Developing new medicines to treat pulmonary fibrosis, one of the most common and serious forms of lung disease, is not easy.

One reason: it’s difficult to mimic how the disease damages and scars lung tissue over time, often forcing scientists to employ a hodgepodge of time-consuming and costly techniques to assess the effectiveness of potential treatments.

Now, new biotechnology reported in the journal Nature Communications could streamline the drug-testing process.

The innovation relies on the same technology used to print electronic chips, photolithography. Only instead of semiconducting materials, researchers placed upon the chip arrays of thin, pliable lab-grown lung tissues — in other words, its lung-on-a-chip technology.

“Obviously it’s not an entire lung, but the technology can mimic the damaging effects of lung fibrosis. Ultimately, it could change how we test new drugs, making the process quicker and less expensive,” says lead author Ruogang Zhao, PhD, assistant professor in the Department of Biomedical Engineering at the University at Buffalo.

The department is a multidisciplinary unit formed by UB’s School of Engineering and Applied Sciences and the Jacobs School of Medicine and Biomedical Sciences at UB.

With limited tools for fibrosis study, scientists have struggled to develop medicine to treat the disease. To date, there are only two drugs — pirfenidone and nintedanib — approved by the U.S. Food and Drug Administrations that help slow its progress.

However, both drugs treat only one type of lung fibrosis: idiopathic pulmonary fibrosis. There are more than 200 types of lung fibrosis, according to the American Lung Association, and fibrosis also can affect other vital organs, such as the heart, liver and kidney.

Furthermore, the existing tools do not simulate the progression of lung fibrosis over time — a drawback that has made the development of medicine challenging and relatively expensive. Zhao’s research team, which included past and present students, as well as a University of

Toronto collaborator, created the lung-on-a-chip technology to help address these issues.

Using microlithography, the researchers printed tiny, flexible pillars made of a silicon-based organic polymer. They then placed the tissue, which acts like alveoli (the tiny air sacs in the lungs that allow us to consume oxygen), on top of the pillars.

Researchers induced fibrosis by introducing a protein that causes healthy lung cells to become diseased, leading to the contraction and stiffening of the engineered lung tissue. This mimics the scarring of the lung alveolar tissue in people who suffer from the disease.

The tissue contraction causes the flexible pillars to bend, allowing researchers to calculate the tissue contraction force based on simple mechanical principles.

Researchers tested the system’s effectiveness with pirfenidone and nintedanib. While each drug works differently, the system showed the positive results for both, suggesting the lung-on-a-chip technology could be used to test a variety of potential treatments for lung fibrosis.