Who else but Scottish engineers would think of using an artificial tongue to differentiate between whiskies? A new paper published in the Royal Society of Chemistry’s journal Nanoscale describe how they built the tiny taster, which exploits the optical properties of gold and aluminium to test the tipples.
Dr Alasdair Clark, of the University of Glasgow’s School of Engineering, is the paper’s lead author. “We’re not the first researchers to make an artificial tongue,” he says, “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.
“While we’ve focused on whisky in this experiment, the artificial tongue could easily be used to ‘taste’ virtually any liquid, which means it could be used for a wide variety of applications. In addition to its obvious potential for use in identifying counterfeit alcohols, it could be used in food safety testing, quality control, security – really 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 reusable optical tongue’s multiplexed gold and aluminium nano-arrays arranged in a checkerboard pattern act as the ‘tastebuds’ in the team’s artificial tongue, a bimetallic device which produces two distinct resonance peaks for each sensing region. Through specific modification of these arrays with orthogonal surface chemistries, such a dual-resonance device could halve sensor sizes and data-acquisition times when compared to single-resonance, monometallic devices.
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. Statistical analysis of the very subtle differences in how the metals in the artificial tongue absorb light – what scientists call their plasmonic resonance – allowed the team to identify different types of whiskies.
Surface chemistry combinations used: (i) native Al, Au (ii) Al-HMDS, Au-DT, and (iii) Al-PEG, Au-PFDT.
The team used the tongue to sample a selection of whiskies from Glenfiddich, Glen Marnoch and Laphroaig. The tongue was able to taste the differences between the drinks with greater than >99.7% accuracy by means of linear discriminant analysis (LDA). 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.
Dr Clark said: “We call this 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.
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.
Only very small samples are required for the testing. We have no information on what happened to the leftover whisky.
