This grant supports research to gain a detailed understanding of the influence of chemical composition on the higher order plane selectivity in silicon anisotropic etching. A polished single crystal silicon sphere, 0.25 inches in diameter is chosen for the study because it provides a systematic tool to measure the plane selectivity in the various etches. Two critical questions will be addressed: the role of the cation in aqueous solutions, and the role of alcohol and other additives to the anisotropy of the etching. The visualization of three dimensional micromachined structures will assist in the design of complex microstructures.