New device can detect surface tension called W-ink

'Watermark ink' device identifies unknown liquids instantly

 Materials scientists and applied physicists collaborating at Harvard's School of Engineering and Applied Sciences (SEAS) have invented a new device that can instantly identify an unknown liquid.  This
'new device changes color when it encounters a liquid with a particular surface tension. '

It is still not available but a chip of this sort could be revolutionary for different applications like 'bootleg liquor for toxic levels of methanol' or  'verify the fuel grade of gasoline right at the pump.'  For now we might have to rely on portable devices that can measure the surface tension.