Towards Technologies Platform and Multifunctionnal Energetic Nano-Materials to manufacture pyroMEMS
Résumé
Energetic materials are the only attractive sources of reliable and "dormant" energy, exhibiting long shelf life and able to very quickly deliver gas, heat, chemical species or, after conversion, electrical power. For example the decomposition of the well-known TNT can produce ~4 MJ/kg in a few tens of µs while a modern chemical lithium battery only stores 0.5 MJ/kg. Therefore, even with a low energy conversion efficiency, energetic materials such as nanothermites remain very attractive to produce-on chips-high-power and high-energy for a wide range of applications such as space transportation systems, medicine, fight against crime, system security…. In practice however, they can be unsafe, unstable and there is no single energetic material able to provide multiple actuations or that excels at every task as the requirements for different tasks might be contradictory: rapid or slow energy release, high or low amount of gas generated. Two decades ago, the introduction of nanotechnologies in the energetic materials field enabled the emergence of a new class of safe energetics called nanothermites. They feature an oxido-reduction reaction involving aluminum and a metallic oxide such as CuO, Fe2O3.... Compared to conventional CHNO pyrotechnical materials, nanothermites are attracting more attention for their high enthalpy of reaction (up to 5 MJ/kg, 16 kJ/cm 3), adiabatic flame temperature (> 2600 °C) and environmentally benign products. Their high surface area gives them a substantially higher energy release rate in comparison to their micron counterparties, thus making them potential candidates for materials whose reactivity fall in between primary explosives and conventional CHNO pyrotechnics. Researchers have been discovering that nanoenergetics, and specifically nanothermites, are particularly well-suited for microdevice applications. The high level of tunability and superior reaction performance in microscale systems makes nanothermites a potential solution for a variety of applications including microthrusters, microactuators, microdetonators, pulse power generators, propellant initiators, and multipoint initiators. Nonmilitary applications of pyroMEMS include airbag inflation initiators, electrothermal switches, needle-free syringes, powder injectors, transfection devices, and others. To realize the full potential of nanoenergetics, however, it is necessary to develop new nano-energetic materials technologies, as well as manufacturing technique, assembly, and packaging methods towards miniaturized, safe and reliable pyrotechnical microsystems. In my talk, I will present the latest research of my team at the LAAS on the area of nanoenergetics to get safe multifunctional energetic materials for pyroMEMS applications. Specifically I will illustrate the interest of nanoenergetics by the presentation of a security microdevice integrating 3D printed safe energetic material together with Al/CuO multilayers.