Fraunhofer ENAS developing ‘1g spectrometer’ for smart phone integration

06 Jul 2021

Aim is to mass-produce the miniature component for €1, targeting diverse self-test applications within two years.

Measurement setup with wafer prober, optical fiber probes and wafer.

Enabling a private individual to spot counterfeit drugs, test water samples, or check the quality of air could be enabled by an innovative, photonics-based adaptation of a smart phone – the incorporation of a tiny, low-cost infrared spectrometer.

Such processes are now being made possible by a spectrometer, weighing just one gram, developed by the Fraunhofer Institute for Electronic Nano Systems (ENAS), in Chemnitz, Germany. The aim is to mass-produce this component for a cost of just one euro (around $1.20) using conventional technologies.

“Our infrared spectrometer weighs only about a gram and we plan for it to cost less than a euro to produce,” said Dr. Alexander Weiß, Head of Multi Device Integration at ENAS. “This will allow it to be integrated into smartphones, for instance.”

At present, infrared spectrometers typically weigh several kilograms and cost thousands of euros to produce. Although transportable devices weighing slightly less do exist, says the ENAS team, they are unsuitable for the mass market – in terms of cost and size and also in terms of operation and analyzing the results.

Other requirements crucial to existing on the mass market: the technology must not be overly complex – in other words, it must be easy to operate – and the production method must be suitable for the mass market.

Various applications

The potential applications are by no means limited to counterfeit drugs. “Our spectrometer lends itself to all kinds of uses – such as assessing the maturity or microbial decomposition of foods for human and animal consumption, measuring the air quality of interiors and vehicles for effective climate control or detecting pollutants in air, water or foodstuffs,” added Dr. Weiß.

As with conventional infrared spectrometers, the new ENAS spectrometer does this by emitting light beams in the infrared range. The light of different wavelengths is then fragmented using a tunable filter and conducted to a detector by means of integrated waveguides. Grating couplers with nanostructures bundle the light reflected by a pill to be tested, for example, into integrated waveguides. If the air quality is to be tested, the light enters a special absorption cell integrated in one plane instead.

So how has the research team reduced the size of the spectrometer so drastically yet still achieve a similar general functionality? “Conventional spectrometers usually consist of discrete more or less well integrated components. We, on the other hand, integrated the beam guidance, the splitting of the individual wavelengths and the detection function in one plane – we are therefore also calling this an inplane spectrometer,” said Dr. Weiß.

Simple and inexpensive

Besides the small size, ENAS wants operation to be easy and intuitive so the system needed to provide the user with clear evaluations. The researchers have already developed a concept: “smart” learning algorithms. “If many people use the technology, the system will learn quickly,” said Weiß.

The user will simply need to pull out their phone, start the spectrometer via a special app and hold it over a test sample. They will also see instructions to guide them through the measurement process. The spectrometer generates the spectrum automatically and the software compares it to reference spectra in a database.

Another sticking point is the cost of producing the spectrometer. The researchers had this in mind from the outset, too. Weiß explained, “We designed the spectrometer such that it could be mass-produced inexpensively using conventional microsystems engineering. Manufacturers can use the processes that are standard in larger fabs.”

The researchers have already produced the first spectrometer chips and provided proof of concept. A number of different characterizations are now on the agenda: do the individual components move as needed? Is the light that is coupled into the waveguide transmitted as wanted? The equipment required for these characterizations has been financed by the Research Fab Microelectronics Germany. If these investigations go as hoped, the team says the spectrometer could be heading to the mass market in around two years’ time.