High Temperature Sensors Using Vertically Aligned ZnO Nanowires

The proposed MEMS sensors can be applied to the measurement of both flow and acceleration in extreme environments and therefore the commercial potential of the technology is broad. Current high temperature flow sensors are limited to optical MEMS and laser-Doppler anemometers. However these technologies have a large probe volume, have not demonstrated accuracy better than 10% under fluctuating shear conditions and do not offer direct, dynamic, time-resolved skin friction measurements with sufficient frequency response and accuracy to resolve transitional or turbulent flows. The proposed sensors can be designed as a surface mount package and does not function based on optical measurements which require costly signal conditioning electronics, thus creating a significant opportunity for commercialization. Beyond future use in flow sensing, the nanowire arrays offer acceleration sensitivity and thus may find use in a wide range of additional applications in structural dynamics or condition monitoring. Accelerometers have become a ubiquitous technology in modern electronics yet require costly and complex manufacturing processes and are unstable in extreme environments. The proposed sensors were shown to be accurate high bandwidth accelerometers while being processed using simple and low cost methods. With this technology being the only MEMS scale accelerometer compatible with the extreme environments found in turbomachinery, the sensors have excellent commercialization potential.

Beyond the specific applications identified for the extreme environments in NASA applications, the proposed sensors can be applied to the broader commercial accelerometer market. MEMS accelerometers currently represent a $1.7 billion dollar market and may be the most successful MEMS technology ever commercialized. While MEMS devices can be produced on a large scale through wafer level manufacturing, they require complex manufacturing processes and costly equipment which has generally been a limiting factor in the production of MEMS devices over the past two decades. The high operation cost of such equipment has also led to a consolidation of the market for MEMS foundry services removing many small businesses. The MEMS scale sensors developed are fabricated without the need for complex and expensive lithography, physical deposition and etching tools that are required in traditional MEMS processing. The proposed nanowire arrays only require a single growth step and can be fabricated onto surfaces or substrates of varying composition. Furthermore, the process does not require the hazardous and environmentally toxic chemicals widely used in traditional MEMs processing. This unique approach will allow the rapid and low cost development of the sensors at HARP Engineering and without significant capital required for equipment purchases. This low cost will provide HARP with a competitive advantage over competing MEMS technologies. More »