The piezo-electric stack exhibits a non-linear response towards higher frequencies.
The frequency response of the piezo-electric stack was non-linear and showed an increased performance towards higher frequencies [22].
We investigated the effect of signal amplification and active actuation of the cantilevers with the integrated piezo-electric stack.
By driving the piezo-electric stack up to 4 - 5 volts we generated optimal detectable resonance peaks at higher modes.
Alternatively the sensors were then actively driven with the piezo-electric stack by applying an actuation voltage within the range of 2 – 5 volts through the software.
The actuation of the piezo-electric stack that was mounted directly underneath the cantilever chip allowed boosting individual sensor frequency responses.
In Figure 8 we report on the quality of the micromechanical resonance spectra of the cantilevers within the array applying an actuation voltage on the piezo-electric stack mounted underneath the cantilever array.
Therefore the implementation of a piezo-electric stack with the size of the cantilever array mounted directly underneath the sensor chip was highly beneficial to boost the sensitivity of the method [39].
The voltage signal of the differential thermal noise on the PSD could be amplified by factors up to 5000 without driving the sensors with the integrated piezo-electric stack.
Above the desk was a shelf with a dictionary, a thesaurus, some packets of restaurant sugar, an electric kettle, a stack of blue and white cups and saucers, a tin of shortbread biscuits and a box of Twinings English Breakfast tea.
Additionally, the shadow effect of non-conductive spacers reduces the membrane area available for counter-ion transport and increases the stack electric resistance.
