In a paper published in the Royal Society of Chemistry’s journal Nanoscale, the engineers from the School of Engineering, at the University of Glasgow, describe how they built the tiny taster, (which is too small to see with the naked eye), which exploits the optical properties of gold and aluminium to test drinks.
'Reusable tastebuds'
The paper states: ‘Metallic nanostructures are ideal candidates for optical tongue devices thanks to their chemical stability, the sensitivity of their plasmonic resonance to environmental changes, and their ease of chemical functionalization’.
The way the reusable ‘tongue’ works is via sub-microscopic slices of two metals, arranged in a checkerboard pattern, which act as ‘tastebuds’.
In tests, the researchers poured samples of whisky over the tastebuds – which are about 500 times smaller than their human equivalents – and measured how they absorb light while submerged.
It applied the bimetallic tongue to differentiate whiskies including Glenfiddich, Glen Marnoch and Laphroaig, with >99.7% accuracy by means of linear discriminant analysis (LDA).
Statistical analysis of the subtle differences in how the metals in the artificial tongue absorb light (plasmonic resonance) allowed the team to identify different types of whiskies.
Dr Alasdair Clark, researcher and lead author on the paper, University of Glasgow, told BeverageDaily the R&D on the project took approximately one year and the technology is in its very early stages.
“We have only tested it in-house, with our own scientists. But we are open to working with any company who would like to take this to the product development stage. However, as a scientific research group this is not our focus,” he said.
“The ‘tongues’ are designed as reusable devices, depending on the application. Should it be commercialised, the most likely form factor would be a tongue integrated within a portable enclosure that also included a spectrometer, a light source, and the associated optical components.
“Depending on the use case you could have individual, single-use tongues that are inserted into (and then removed from) the device, or you could just have a permanently located tongue that is ‘washed’ after every use.”
Clark added ‘artificial tongues’ already exist, and there are lots of different ways to make them.
“We specialise in building nano-scale materials that react to light. We saw an opportunity to build an artificial tongue that worked on these principles. We believed we could make one that was a little smaller and more complex (in terms of the composition of its artificial taste-buds) than had been seen before.
>99.7% accuracy
“The tongue was able to taste the differences between the drinks with greater than 99% accuracy. It was capable of picking up on the subtler distinctions between the same whisky aged in different barrels, and tell the difference between the same whisky aged for 12, 15 and 18 years.”
Clark said the team decided to call the technology an ‘artificial tongue’, because it acts similarly to a human tongue – like us, it can’t identify the individual chemicals which make coffee taste different to apple juice but it can easily tell the difference between these complex chemical mixtures.
“We’re not the first researchers to make an artificial tongue, but we’re the first to make a single artificial tongue that uses two different types of nanoscale metal ‘tastebuds’, which provides more information about the ‘taste’ of each sample and allows a faster and more accurate response,” he added.
The researchers focused on whisky as part of the experiment, but the device can be used to ‘taste’ any liquid, which means it could be used for a variety of applications.
In addition to its potential for use in identifying counterfeit alcohols, it could be used in food safety testing, quality control, security and any area where a portable, reusable method of tasting would be useful.
The paper, titled ‘Whisky tasting using a bimetallic nanoplasmonic tongue’, is published in Nanoscale.
The report concludes: ‘We have presented a reusable bimetallic nanoplasmonic tongue that displays two distinct resonance peaks per region and whose orthogonal surface chemistries can be selectively modified to tune their ‘tasting’ sensitivity.
‘These unique features have allowed us to halve both the sensor size and necessary data-acquisition time while still providing dataset clustering upon PCA and successful classification with linear discriminant analysis (LDA).
‘This is a versatile system, allowing the development of high quality nanoplasmonic tongues for any given application via simple alterations to the chosen surface ligands and/or plasmonic metals to produce new sensors with unique chemical responses.
‘This new approach to artificial tongue design may spur the development of portable devices for applications in a point of care diagnostics, counterfeit detection in high-value drinks, environmental monitoring, and defense’.
The research, which was conducted by engineers and chemists from the Universities of Glasgow and Strathclyde, was supported by funding from the Leverhulme Trust, the Engineering and Physical Sciences Research Council, and the Biotechnology and Biological Sciences Research Council.
Source: The Royal Society of Chemistry 2019
Researchers: School of Engineering, University of Glasgow
DOI: 10.1039/c9nr04583j
Received: May 29, 2019,
Accepted: June 26, 2019
Authors: Gerard Macias, Justin R. Sperling, William J. Peveler, Glenn A. Burley, Steven L. Neale and Alasdair W. Clark.
