Material and structure sensors

Mechanical load detection for lightweight materials#

© Fraunhofer ENAS
Sensor film (electro-optical transducer) and piezoelectric transducer integrated in fibre-reinforced plastic.

Optical information are an integral part for our actions in daily life. Electro-optical transducers based on quantum dots detect electrical information and store them without further energy consumption. Thus, the information can be optically read out at a later time, whereby the electro-optical transducers based on quantum dots offer a large variety of applications for event and condition monitoring. In combination with a force sensitive element, the stored information can be used as an indicator of the condition or mechanical load of lightweight materials.
A sensor film based on quantum dots, developed by Fraunhofer ENAS in cooperation with the Center for Microtechnologies of Chemnitz University of Technology, offers the basis for such transducers. Their flexible shape makes them easy to integrate into lightweight materials. In the initial state, UV light is transformed into visible light with a certain initial light intensity. Due to mechanical load, electrical charge carriers (< 50 nC/mm²) are injected into quantum dots within 1 ms via the system of electrodes and the process of photoluminescence (PL) is prevented. As a result, the intensity of the visible light is reduced, which can be used as an indicator of the applied mechanical load on the lightweight material even after more than 60 hours. Due to this development the state of the lightweight component can be determined more quickly and allows taking action in a timely manner. Thus, leading to a gain in security that is also a possible solution for many other applications.
The work was performed within the Federal Cluster of Excellence EXC 1075 »MERGE Technologies for Multifunctional Lightweight Structures« and supported by the German Research Foundation (DFG). Financial support is gratefully acknowledged.