ES1 sensor: smallest electrochemical sensor in the world Solid polymer electrolyte gas sensors

from VOC sensing to long-life oxygen gas sensors

Solid polymer electrolyte (SPE) gas sensors offer flexibility in design and size, because the basic sensor design is dry and contains no liquid electrolytes. Liquid electrolyte gas sensors, also known as wet electrochemical cells, are used in many applications ranging from automotive (fuel usage optimization) over industrial (safety) and to emission control (surveillance). Because of the wet current carrying electrolyte, the mechanical design is essential for operation and lifetime of the cell. Over the last 20-30 years certain popular wet electrochemical cell designs have become standard – like the 4-series (diameter 20 mm) for handheld gas analyzers and the 7-series (diameter 32 mm) for stationary gas analyzers. The concept of a dry electrochemical cell based on a solid polymer electrolyte challenges not only the design restrictions of the gas sensor, but also the traditional applications for electrochemical cells.

A dry electrochemical cell has a polymer as basis and chemistry for the electrochemical reactions embedded in the polymer layer. This enables new and innovative mechanical designs for the finished cell. An example of such a new design is shown in the figure below. The ES1 sensor is the smallest electrochemical sensor in the world. The ES1 cell size has been reduced in all dimensions allowing for small and more compact gas analyzers to be build. The gases that can be detected using the SPE technology are many. The first generation ES1 gas sensors have been developed for emission control and monitoring of gases such as O2, CO, NO2, H2S, H2 and volatile organic compounds (VOCs).

The SPE technology support high volume production strategies, because the layers are printed onto a carrier substrate. This is also new in the gas sensor industry and will enable new applications in for instance home appliances and intelligent air conditioning. The power needed to drive the circuit is so low that battery operation and remote applications relying on long battery lifetimes are becoming feasible strategies for new product developments based on the ES1 SPE gas sensors.

The ES1 line of gas sensors comes with different standard measurement ranges, but other measurement ranges are also possible, because the SPE technology allows specific custom designs. Other parameters that can be varied in order to fit certain applications are the response time of the sensor and the sensitivity of the sensor. The sensors are individually calibrated and a test report comes with every sensor. The expected lifetime of the ES1 sensors is more than 3 years.