In-vacuum dry launching of silica microparticles using an array of custom MEMS devices

To test the validity of the quantum superposition principle at unprecedented macroscopic scales, near-field matter-wave interferometry of free-falling massive 100nm silica nanospheres from an optically cooled laser trap has been proposed [Nat. Commun.5, 4788 (2014)10.1038/ncomms5788]. This could be realized with available technology, providing the emerging technical challenge of in-vacuum dry loading the optical trap with single 100nm silica particles, in a deterministic, repetitive, and clean manner, is addressed. Here, for the first time to our knowledge, we demonstrate, both theoretically and experimentally, a 3×3 array of custom micro-electro-mechanical system (MEMS) storage and release devices for this objective. The fabricated MEMS devices are square ultrasonic flexural silicon membranes, 400<i>μ</i>m in side length and 8<i>μ</i>m in thickness, monolithically integrated with a 1<i>μ</i>m thick aluminium nitride piezoelectric transducer. The ability of the MEMS array to launch 9.98<i>μ</i>m, 4.23<i>μ</i>m, and 900nm silica particles in vacuum was tested experimentally using our recently developed GRIN lens-based digital holographic 3D imaging system integrated into a vacuum chamber. The minimum particle size released from the current devices is ∼4<i>μ</i>m in diameter with the average lateral release speed in the range of 3-35 cm/s. The experimental results obtained are in good agreement with the theoretical predictions.