Inertial sensors for motion detection are being incorporated into an increasing number of portable devices, including diverse IoT applications, mobile phones, wearable electronics, automotive systems and medical diagnostic sensors. The current size reduction trend in electronics, requires incorporation of reliable nanoelectromechanical systems (NEMS) into nanosensors, yet market applications of NEMS are currently limited by high costs of fabrication and inconsistent quality. A new technology developed by a group of researchers from the Weizmann Institute, provides a unique, highly reproducible structure for inertial nanosensors, with high durability at the nanoscale and with a detection mechanism based on the piezoresistive effect. The invention further extends application opportunities of extremely small portable electronics, which, with the increasing use of spatial awareness in reduced size electronics and IoT, is expected to witness increasing market demand.
- Nanoscale (pedal dimensions of >300x800 nm)
- The output is an electrical signal
- Based on inorganic nanotubes with high durability, allowing extended time operation
- High accuracy and sensitivity
- (torsional resonance frequency of 20 ± 4 MHz).
- IoT devices
- Navigation systems
- Wearable sensors (smart watches and fitness trackers)
- High-resolution camera stabilization
- 3D gaming
- Medical implants and devices.
A novel structure for inertial sensors with a motion detection mechanism based on the piezoresistive effect that enables drastic size reduction of the sensing device to the nanoscale. The novel device incorporates inorganic nanotubes for increased sensitivity and reliability (published in: Nano Lett. 2017, 17;1: 28-35). The structure of the inertial sensor consists of a suspended nanotube clamped between metallic pads at its ends, with a suspended pedal attached at the top (see Figure 1). The pedal is off-centered with respect to the nanotube, so each end of the pedal stands at a different distance from the nanotube. The structure was fabricated using electron-beam lithography, followed by wet-etching and critical point drying. In order to measure the oscillatory behavior of the torsional resonators, a DC bias voltage and a smaller AC drive voltage are applied between the substrate and the pedal. The alternating voltage between the substrate and the pedal combined with the offset of the center of the pedal with respect to the nanotube, creates an oscillatory net torque on the pedal, leading to periodic twisting the nanotube. The pedal vibration detection can be detected using an electric signal.
(a) Scanning electron microscope image and (b) atomic force microscope image of the nanotube-based inertial sensor. (c) The inertial sensor is actuated by applying voltage between the substrate and the offset pedal, which is attached to the nanotube.