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Silicon can be converted into porous silicon (PS) through a galvanic etch process and then rendered energetic when infused with any one of a number of oxidizers. Energetic PS can provide variable energy release to generate thrust and the displacement of small-scale devices such as microthrusters and micro-satellites. In this report, we investigate the etch process and its repeatability for pore formation during etches. We found that using a fresh etch bath reduces variability in pore characteristics. In addition, we examine the thrust output of a combustion reaction of PS activated with sodium perchlorate. Experimental testing showed that the forces ranged from tens to hundreds of millinewtons, depending on the silicon wafer resistivity and pore morphology, which is controlled by the etch parameters., The original document contains color images.

Parylene film is attractive for hermetic encapsulation of porous surfaces, including energetic materials, and for the protection of integrated circuits on large-diameter silicon substrates. Achieving uniformity and repeatability of chemical vapor deposited (CVD) parylene film on large-diameter wafers in a batch system is challenging. The difficulties are related to improper selection of the wafer attachment apparatus in the chamber, and the poor coating repeatability from run to run is attributed to wafer volume changes in the CVD chamber. We discuss hardware modifications and preparation methods that improve the predictability, uniformity, and adhesion of the parylene film on nanoporous silicon surfaces. Atomic force microscopy (AFM) can determine surface roughness and distinguish differences in nanoporous silicon etched surfaces. Energetic materials that are hygroscopic in nature need to be protected from the environment during storage to improved ignition lifetime. Parylene film is an effective moisture barrier for nanoporous-scale material applications. We tested the adequacy and lifetime of parylene protection layer for a nanoenergetic device and found the shelf life can be extended in environments with greater than 80% humidity., The original document contains color images.

Nanoporous silicon with sodium perchlorate oxidizer was examined as an igniter of bulk JA2 propellant. Electron microscopic postmortem examination of the propellant after the first experiment suggested the use of an additional igniter material. Nano bismuth oxide and nano cuprous oxide thermites were both attempted as supplemental igniter materials. The nano bismuth oxide thermite did not ignite the JA2, but the nano cuprous thermite did successfully provide ignition., The original document contains color images.

As the capability and complexity of robotic platforms continue to evolve from the macro to micro-scale, innovation of such systems is driven by the notion that a robot must be able to sense, think, and act [1]. The traditional architecture of a robotic platform consists of a structural layer upon which, actuators, controls, power, and communication modules are integrated for optimal system performance. The structural layer, for many micro-scale platforms, has commonly been implemented using a silicon die, thus leading to robotic platforms referred to as "walking chips" [2]. In this thesis, the first-ever jumping microrobotic platform is demonstrated using a hybrid integration approach to assemble on-board sensing and power directly onto a polymer chassis. The microrobot detects a change in light intensity and ignites 0.21mg of integrated nanoporous energetic silicon, resulting in 246µJ of kinetic energy and a vertical jump height of 8cm.

Nano-porous silicon offers a large surface area to volume ratio typical of nano materials and contains a network of pores that can be filled with oxidant. When a silicon fuel source is combined with an oxidant on the nano-scale, kinetic limitations of silicon oxidation are overcome and an explosive reaction is realized. We present a characterization of lightly doped p-type silicon for nanoenergetic porous silicon (PS) applications. Using gas adsorption measurements and gravimetric techniques, we characterize pore size, porosity, specific surface area, and thickness of PS thin films. Additionally, we report on the energetic reaction of the PS/oxidant system and mechanical stability of PS formed under several etch conditions including varied etch current, drying techniques, and annealing. Prior research has not focused on sample preparation methods of PS for gas adsorption measurements, but results presented here indicate that the method of PS sample preparation for gas adsorption isotherm analysis impacts the results. We find that a newly reported gravimetric technique for PS parameter characterization is inconsistent with expected PS property trends for lightly doped p-type Si., The original document contains color images.

While research has focused on the optical properties of nanoporous silicon and its use as an isolation material in integrated circuits, there is a great deal to be gained by understanding the formation process of such a versatile material. The structure itself is made up of millions of pores that are formed through an electrochemical wet etch, which results in network clusters of nanoporous material with a surface area on the order of 50 m sq/g. In this report, we explore the process of preparing the nanoporous silicon, while presenting solutions to some of the challenges that arise during the pore formation. These challenges include cracking of the nanoporous layer when attempting to etch pores with a vertical depth greater than ~35 m, as well as effects of electric field concentrations in the etch process, which degrade structural integrity. In addition we provide a quantitative analysis of the material's structural layer and present an alternative approach to the current wet etching technique., The original document contains color images.

en. (Also cross-referenced as UMIACS-TR-2001-67, HCIL-TR-2001-21)