Non-electrical sensing and storing an alternative to electrical energy harvesting

In many applications, a summarized result, e.g. the number of critical off-limit conditions or an integral result over a specific period of time are of interest to draw implications for the future. Among these applications are the shelf life monitoring of consumables, pharmaceutics or food as well as the condition monitoring of technical infrastructure. Sensors usually require an electrical energy source for measurement and storage of data. Here, two non-electrical examples are presented that register data without the need of electrical energy: a passive temperature-time integrator (TTI) and a mechanical binary counter for threshold events. The TTI makes use of microfluidic flow of specific food ingredients into microcapillaries that depends on viscosity and time. The binary counter based on surface MEMS allows counting and storing threshold events, e.g. mechanical shocks. Both sensors can easily be read out e.g. by RFID

Self-sufficient sensor for oxygen detection in packaging via radio-frequency identification

A new disposable radio-frequency identification (RFID) sensor for detecting oxygen in packages with a protective atmosphere is presented. For safety reasons and system costs in consumer packages, no battery or energy harvesting devices can be used. Each part of a package, especially in food packaging, must be completely safe even if it is swallowed. Several materials have been investigated that safely react with oxygen and thus change electrical parameters without the need of an additional energy supply. In particular linseed oil was tested, because it is known to react in oxygen-containing atmosphere from liquid to solid. Linseed oil is used not only as food but also as a key part in ecological paint coatings. A significant relative change of capacity was observed during linseed oil drying, which results in −20% after 5 h and −38% after 30 h at an oxygen concentration of 20.5 and 50% relative humidity, respectively. Pure unsaturated fatty acids were also tested in an oxygen-containing atmosphere and showed similar behaviour. The reaction speed is partially dependent on the level of unsaturation of fatty acids. The oxygen sensor is coupled with an RFID front end with an internal charge time measurement unit for capacity determination. The combination of sensor element, sensitive material and RFID allows for biocompatible and save systems that indicate the presence of oxygen within a package

Schiller als Weltbürger und Freund seines Vaterlandes

von Reinhard JurischIn FrakturProgr.-Nr. 20