Smart aluminum components: Printed sensors for integration into aluminum during high-pressure casting

We present a new and innovative approach for the direct integration of sensors into aluminum during casting to obtain strain and temperature data for the aluminum. This technology will enable a variety of new applications in sensing technology such as sensing car parts in the automotive industries (e.g., a suspension arm), innovative parts of an exoskeleton with integrated sensors for feedback information, or sensing structural components of vehicles. Furthermore, these sensors can result in more efficient quality assurance, are fully encapsulated against environmental influence, provide an ideal connection between sensor and metal matrix due to integration in the casting process, and enable engineers to place sensors directly at the place of interest without limitations. To reach the goal of integrating sensors in aluminum, we first focus on silicon-based sensors. We will show that sensor integration is possible, but the failure rate is high. This is analyzed by evaluating sensor data during casting. Due to the high difference in coefficiency of thermal expansion between aluminum and silicon, high thermal-induced compressive stress is generated in the silicon and is destroyed in the casting process during solidification cooling. This is why we convert in the second part of this paper to a new sensor concept, which is adapted to the conditions of the casting process. A sensor and its electrical connections are printed on aluminum sheets and integrated in aluminum in an industrial high-pressure casting process. As a result of these pre-tests, more than three-quarters of the devices survived the process of integration. Finally, we show that we obtain strain and temperature data from the cast part to develop smart components out of cast aluminum and to enable new sensing technologies.