Aid for visually impaired people

Z-axis MEMS Accelerometer

Z-axis MEMS Accelerometer for Vibrotactile Display Pad

Technology: X-FAB MEMS XMB10

Dr. Ali Mohammadi, Steven Ng

Mitigating the resolution bottleneck


Assistive technologies such as Braille and swell papers have been evolved to digital tactile displays, which help the visually impaired (VI) individuals to receive graphical information through the sense of touch. 


To mitigate the resolution bottleneck of existing tactile displays, we have developed a new high-resolution vibrotactile display technique following the feedback received from researchers in the Departments of Computer Science, Psychology and Education.

Developing a sensor solution


Our technique allows one electromagnetic coil to selectively vibrate multiple smaller tactile pixels (taxels) based on their mechanical resonance frequency.


We now investigate the integration of tactile sensing mechanism in the new actuator to control the vibration of tactile elements.

Thereby, we have embedded off-the-shelf piezoelectric sensors underneath the taxels to track the resonance frequency of the taxels. However, the bulky size of these sensors avoids using individual sensors especially in the high-resolution taxel configuration, whereby multiple taxels are implemented within a small area.


In this project, we have designed capacitive MEMS sensors in XFAB processes to measure the vibration of 3D printed taxels. The capacitive sensors built in XMB10 processes will measure the displacement of taxels in Z direction and supply the measured output as the feedback signal to the actuator input.

Increasing accuracy of taxel tracking


This sensor will allow the implementation of a closed-loop control system to accurately track the resonance frequency of taxels. In addition, the proposed sensor will create an interactive and bilateral communication to receive tactile input from the user.

SEM image of the z-axis accelerometer with comb finger capacitive transducers for sensing and actuation purposes.

Harmonic analysis in Coventor MEMS+ shows the resonant modes in X, Y and Z direction.

The proof mass deflection in the heavier side is larger than the lighter side, which is needed for measuring out-of-plane acceleration.