Effects of biomedical sterilization processes on performance characteristics of MEMS pressure sensors.

The effects of steam and gamma sterilization on the performance of bulk-micromachined pressure sensors were investigated using a variable pressure setup. Commercially available piezoresistive MEMS (microelectromechanical systems) pressure sensor die were characterized prior and subsequent to sterilization over a 0-500 Torr pressure range. The effects of sterilization were examined as changes in sensor output voltage (DeltaV) at various applied pressures. For steam sterilization, DeltaV decreased with applied pressure ranging from +0.27 mV at 100 Torr to -0.14 mV at 500 Torr. In contrast, the corresponding values for gamma-sterilized sensors were lower, decreasing from +0.01 mV 100 Torr to -0.06 mV at 500 Torr. The increased variation in DeltaV for the steam-sterilized sensors was attributed to the formation of an oxide film, which was confirmed using energy dispersive X-ray (EDX) spectroscopy. Statistical analysis revealed that the effect of both sterilization procedures on sensor performance was insignificant.

Dialysis and nanotechnology: now, 10 years, or never?

Nanotechnology, defined as the science of material features between 10(-9) and 10(-7) of a meter, has received extensive attention in the popular press as proof-of-concept experiments in the laboratory are published. The inevitable delay between feature articles and clinical endpoints has led to unwarranted skepticism about the applicability of the technology to current medical therapy. The theoretic advantages of micro- and nanometer scale engineering to renal replacement include the manufacture of high-hydraulic permeability membranes with implanted sensing and control structures. Recent data in membrane design and testing is presented, with a review of the challenges remaining in implementation of this technology.

Silicon dermabrasion tools for skin resurfacing applications.

Miniature abrasion tools for potential skin resurfacing applications are created using microelectromechanical systems (MEMS) fabrication technology. The abrading microstructures are formed on silicon wafers by a bulk micromachining process based on isotropic xenon difluoride etching. The micromachined abraders (microdermabraders) are packaged and applied to human cadaveric skin to assess abrasion quality. Plastic (acrylic) microreplicated structures, non-coated and aluminum-coated versions, are also used in a similar fashion. Non-textured silicon and plastic samples are used as study controls. Dermabraded and intact skin regions are analyzed qualitatively and quantitatively by light microscopy, image processing techniques, and histology. The microdermabraders exhibit a cleaner, more uniform abrading pattern on the cadaveric skin compared to the plastic microreplicated structures. Furthermore, the microdermabraders provide a consistently uniform cut through the epidermal layer, leaving little debris and minimal pitting. In contrast, the plastic microreplicated structures exhibit non-uniform abrading patterns and leave behind more debris and eccentric pits. The results suggest micromachined dermabraders can successfully abrade fine dermatological flaws in human skin.

Microelectromechanical systems and neurosurgery: a new era in a new millennium.

MICROMACHINES AND MICROELECTROMECHANICAL SYSTEMS (MEMS) are terms that are new to neurosurgeons but certain to become "household terms" in neurosurgery in the near future. These new terms serve as an introduction to a new world of sensors, actuators, and "smart systems" that will change the ways in which neurosurgeons interact with their environment. Through the use of microelectronics and micromachining technologies, MEMS will allow neurosurgeons to perform familiar tasks with greater precision, perform tasks that previously were not done at all, and monitor physiological and biochemical parameters more accurately and with greater safety. This review provides the information necessary to understand the fundamental concepts of MEMS and their application to the neurosurgical arena. It defines the relevant terms and describes the history behind the "micromachine revolution," the capabilities and limitations of MEMS technology, and how this revolution is germane to neurosurgery and to neurosurgeons.