NIRVANA

Motivation

The need for very low cost and very low power consumption inertial sensors is exploding with the recent introduction of these sensors on mobile phones, game terminals, iPad, GPS etc. Moreover, complex motion features are now required by the application thus leading to use not only one modality of sensor (like accelerometer only) but also combos (6-axis or 9-axis sensors, combining accelerometers and gyroscopes, accelerometers and magnetometers, or all sensors simultaneously). These sensors are used for motion sensing in various applications:

 

  • Handheld device (remote control, mice, mobile phone, ...)
  • Physical Activity monitoring
  • Situational awareness (power management, hard disk drive protection)
  • Image stabilization for camera phones (pitch and roll motion detection)
  • Localization (e. g. dead reckoning)
  • Rehabilitation

For most of these applications, where accurate motion sensing is needed, a 9-axis inertial sensor composed of 3-axis accelerometer (mainly for linear displacement capture), 3-axis gyrometer (for yaw, roll and pitch capture) and 3-axis magnetometer (to determine heading), is required. The need for very small and very low power consumption inertial sensors is also emerging in high-end markets such as medical fields. These sensors are candidate to be used for sensing e.g. of motion, vibration, sound in novel applications, like:

  • Functional vestibular prosthesis for rehabilitation of severe balance dysfunction
  • Implantable hearing solutions e.g cochlea implants and middle ear implants
  • Life monitoring e.g. within cardiac pacemakers



Implementation

The main objective of NIRVANA project is to propose an innovative sensor concept and technology based on the use of nano-scale detection means, which allow both, a high degree of miniaturization and a full integration of a low cost 9-axis inertial sensor for accurate motion sensing.The main outcomes of the projects will be a '9-axes' sensor targeted for consumer applications and a '3-axes' gyroscope for medical applications. In particular the '9-axes' sensor specification will be set according to the requirements of the end users ST Microelectronics and Movea, while the specification of the '3-axes' gyroscopes in order to satisfy the requirements for vestibular implantation of the device, required by MED-EL.

Nine-axis sensor based on nano-gauges detection

The M&NEMS process developed at Cea-LETI labs, enabled the fabrication on a same device of a thick MEMS layer for the inertial mass with a thin and narrow NEMS part as suspended strain gauge. Based on this process it is possible to realize highly-integrated, low-power and low-cost sensors. 

 

In Figure it is represented a uni-axis accelerometer based on this process:

  1. An inertial mass is suspended on a substrate by one of its extremities by a hinge anchored to the substrate
  2. A suspended nanogauge is fixed from one side to an extremity of the mass and from the other side to an anchor. This nanogauge is a simple silicon suspended beam used as a piezoresistive gauge.

Acceleration induces a rotation of the mass around the hinge axis which creates tensile or compressive stress in the gauge, causing a change in the resistance of the gauge. High sensitivity can be obtained with high stress concentration produced by the very small cross-section of the silicon nano-wire, and also by designing the device in order to have a lever effect (see Figure). The stress amplification can tipically reach a factor of 100. 

September - 2019
MoTuWeThFrSaSu
      1
2345678
9101112131415
16171819202122
23242526272829
30