Solid-state multi-ion sensor is an IoT breakthrough
13-12-2016 | By Paul Whytock
A tiny sensor that determines pH and chloride levels in fluid simultaneously has been demonstrated by research organisation Imec and the Holst Centre. It will provide accurate measurement of ion concentrations in applications ranging from health diagnostics to agriculture.
Imec and the Holst Centre say its electrode design results in a similar or better performance compared to today’s standard equipment for measuring single ion concentrations and also facilitates additional ion-related tests.
When it comes to the Internet of Things (IoT) the sensor is claimed to be an industry first thanks to the use of System on Chip (SoC) integration.
Sensors based on ion-selective membranes are considered the gold standard to measure ion concentrations in many applications. They consist of two electrodes, the ion-sensitive electrode with the membrane (ISE) and a reference electrode (RE). When these electrodes are immersed in fluid a potential is generated that scales with the logarithm of the ion activity in the fluid thereby forming a measure of its concentration.
However, the precision of the sensor depends on the long-term stability of the miniaturised RE, a recognised technical challenge that Imec says has now been resolved.
The issue with such designs is the leaching of ions from the internal electrolyte and to stop this an RE was created with a microfluidic channel as a junction combined with solid-state iridium oxide and silver chloride electrodes fabricated on a silicon substrate.
