Using MEMS to Control Blending at AstraZeneca

By Peter J. Brush, Ph.D., and Albert W. Alexander, Ph.D., both senior scientists at AstraZeneca Pharmaceuticals It is also important that the instruments can be used from pilot- to production-scale blenders in order to follow the development of a pharmaceutical product. NIR spectroscopy has previously been used for on-line blend monitoring using instruments based on diode array and acousto-optical tunable filter technologies. (6) This paper discusses the application of a MEMS-based NIR spectrometer for on-line monitoring of powder blending in a rotating bin blender. MEMS is an acronym for Micro Electro Mechanical Systems and are tiny, micro-fabricated devices that can be found in a variety of industries including defense (munition guidance, surveillance), automotive (tire pressure, air bag sensors), electronics (projection screen TVs, ink jet printing heads, video game controllers) to name a few. MEMS is an expansion of the tools and manufacturing methods existing in the microelectronics industry and, unlike typical integrated circuits, these devices will have some non-electronic function as well such as sensing, communication or actuation. MEMS application to spectroscopy means that the now-bulky optical/mechanical part of a spectrometer can be miniaturized to match the microelectronic solutions that are currently available. This combination produces a combined microoptic-micromechanical-microelectronic system. Advantages of MEMS-based NIR spectrometers are their small size and weight, and, since these spectrometers can be machine-made and mass-produced, the resulting instruments are nearly identical, have 20+ lifetimes, and, eventually, will become less expensive. (7) Recently, MEMS-based systems have been used in the pharmaceutical and chemical industries for raw material identification, solvent recovery and dryer control and monitoring (8). The instrumentation used for this work is an Antaris Target blend analyzer (Thermo Electron Corp.). This device is a MEMS-based NIR analyzer with a spectral range of 1350 – 1800 nm. The spectrometer is configured with a semiconductor-based NIR tunable laser