The use of Additive Manufacturing (AM) processes for space and terrestrial applications is a constantly growing topic of interest from the main actors in the industry. In the perspective of its future developments in the space field and for terrestrial applications, CSEM tackled the challenge of producing compliant structures based on SLM (Selective Laser Melting). In this framework, high performance stainless steel flexures with thickness below 380 micron offering bending fatigue resistance above 15 million cycles under realistic load cases were produced. On the other hand topology optimization software and specific design rules are applied to produce optimized structural parts and monolithic compliant structures. The second part of this paper describes the successful redesign of electrical SlipRings Assemblies (SRA) rotors intended for space applications. This project was run jointly with RUAG Space Switzerland, based on their expertise in the field of space grade SRAs and thanks to the know-how developed by CSEM in the field of AM-based mechanical (re)design. The novel architecture based on the combination of additive manufacturing, casting and remachining enables a significant reduction of the manufacturing and assembly costs and risks.
Previously, the realization and closed loop control of a MEMS scanner integrating position sensors made with piezoresistive sensors was presented. It consisted of a silicon compliant membrane with integrated position sensors, on which a mirror and a magnet were assembled. This device was mounted on a PCB containing coils for electromagnetic actuation. In this work, the reliability of such system was evaluated through thermal and mechanical analysis. The objective of thermal analysis was to evaluate the lifetime of the MEMS scanner and is consisting of temperature cycling (-40°C to 100°C) and accelerated electrical endurance (100°C with power supplied to all electrical components). The objective of mechanical analysis was to assess the resistance of the system to mechanical stress and is consisting of mechanical shock and vibration. A high speed camera has been used to observe the behavior of the MEMS scanner. The use of shock stopper to improve the mechanical resistance has been evaluated and had demonstrated a resistance increase from 250g to 900g. The minimum shock resistance required for the system is 500g for transportation and 1000g for portative devices.
We report on the use of the bulge test method to characterize the mechanical properties of miniaturized buckling-mode dielectric elastomer actuators (DEA). Our actuator consists of a Polydimethylsiloxane (PDMS) membrane bonded to a silicon chip with through holes. Compliant electrodes are fabricated on both sides of the membrane by metal ion implantation. The membrane buckles when a critical voltage is applied to the electrodes. The maximum displacements as well as the efficiency of such actuators strongly depend on the mechanical parameters of the combined electrode-elastomer-electrode layer, mainly effective Young's modulus E and residual stress &sgr;. We report measured E and &sgr; obtained from bulge tests on PDMS membranes for two PDMS brands and for several different curing methods, which allows tuning the residual stress by controlling the rate of solvent evaporation. Bulge test measurements were then used to study the change in membranes' mechanical properties due to titanium ion implantation, compared to the properties obtained from depositing an 8 nm thick gold electrode. At the doses required to create a conductive layer, we find that the Ti ion implantation has a low impact on the membrane's overall rigidity (doubling of the Young's modulus and reducing the tensile stress) compared to the Au film (400% increase in E). The ion implantation method is an excellent candidate for DEAs' electrodes, which need to be compliant in order to achieve large displacements.