Gauge Factor Tuning, Long-Term Stability, and Miniaturization of Nanoelectromechanical Carbon-Nanotube Sensors

Integrated piezoresitive strain gauges are established transducers for measuring displacements in microelectromechanical systems (MEMS). Due to large gauge factors (GFs) and low power operation and nanometer dimensions, carbon nanotubes (CNTs) are ideal candidates for further downscaling strain-gauge-based MEMS devices. Here, we present zero-level packaged strain gauges based on individual single-walled CNTs in a field-effect transistor configuration, which can be utilized as long-term stable and tunable transducers for measuring membrane deflections in ultraminiaturized pressure sensors. The gate electrode allows adjusting GFs of nanotube strain gauges by almost a factor of 10. Studies on nanotube segments of different lengths show highly reproducible GFs along the same CNT. The zero-level packaged pressure sensors show stable GFs over a period of at least 14 months. This paper is an important step toward reliable nanoscaled strain gauges with many potential applications, such as ultraminiaturized pressure-sensitive membranes or cantilever-based transducers.