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This paper reports the design, fabrication, and experimental characterization of a fully microfabricated planar array of externally fed electrospray emitters that produces heavy molecular ions from the ionic liquids EMI-B[F.sub.4] and EMI-Im. The microelectromechanical systems (MEMS) electrospray array is composed of the following two microfabricated parts: 1) an emitter die with as many as 502 emitters in 1.13 [cm.sup.2] and 2) an extractor component that provides assembly alignment, electrical insulation, and a common bias voltage to the emitter array. The devices were created using Pyrex and silicon substrates, as well as microfabrication techniques such as deep reactive ion etching, low-temperature fusion bonding, and anodic bonding. The emitters are coated with black silicon, which acts as a wicking material for transporting the liquid to the emitter tips. The extractor electrode uses a 3-D MEMS packaging technology that allows hand assembly of the two components with micrometer-level precision. Experimental characterization of the MEMS electrospray array includes current-voltage characteristics, time-of-flight mass spectrometry, beam divergence, and imprints on a collector. The data show that with both ionic liquids and in both polarities, the electrospray array works in the pure ionic regime, emitting ions with as little as 500 V of bias voltage. The data suggest that the MEMS electrospray array ion source could be used in applications such as coating, printing, etching, and nanosatellite propulsion. [2008-0270] Index Terms--Black silicon, electrospray array, ion source, ionic liquid, 3-D packaging.

This paper reports the design and experimental validation of an in-plane assembly method for centimeter-scale bulk-microfabricated components. The method uses mesoscaled deep-reactive-ion-etching (DRIE)-patterned cantilevers that deflect and lock into small v-shaped notches as a result of the hand-exerted rotation between the two components of the assembly. The assembly method is intended for MEMS arrays that necessitate a 3-D electrode structure because of their requirement for low leakage currents and high voltages. The advantages of the assembly method include the ability to decouple the process flow of the components, higher overall device yield, modularity, reassembly capability, and tolerance to differential thermal expansion. Both tapered and untapered cantilevers were studied. Modeling of the cantilever set shows that the springs provide low stiffness while the assembly process is in progress and high stiffness once the assembly is completed, which results in a robust assembly. In addition, analysis of the linearly tapered cantilever predicts that the optimal linearly tapered beam has a cantilever tip height equal to 37 % of the cantilever base height, which results in more than a threefold increase in the clamping force for a given cantilever length and deflection, compared to the untapered case. The linear taper profile achieves 80% of the optimal nonlinear taper profile, which would be impractical to fabricate. Analysis of the experimental data reveals a biaxial assembly precision of 6.2-[micro]m rms and a standard deviation of 0.6 [micro]m for assembly repeatability. Electrical insulation was investigated using both thin-film coatings and insulating substrates. Leakage currents less than 1 nA at 2 kV were demonstrated. Finally, this paper provides selected experimental data of a gated MEMS electrospray array as an example of the application of the assembly method. [2008-0113] Index Terms--Electrospray, high-voltage MEMS packaging, MEMS hand assembly.