Sensors that produce a measurable response to the applied mechanical deformation are useful in many applications including personal and structural health monitoring. One of the ways to make these strain sensors by fabricating small string-like vibrating structures called nanoresonators. These tiny (sub 10um) structures, made of materials such as graphene, vibrate at very high frequencies (10-100MHz) and are exquisitely sensitive to changes in the strain. However, introducing the strain stimuli into these sensors implies that the devices have to fabricated on flexible substrates such as PDMS and PET. The fabrication process on these substrates is complex and device yields are small.
Swapnil More has developed a simple method to fabricate these devices on a thin diaphragm on silicon substrates. He then utilized air pressure to deform the substrate on which NEMS are fabricated. This controlled deformation of the substrate induces strain in the nano resonator and changes the resonant frequency. The magnitude of this strain change can be deduced using the frequency tuning of the nano resonator. We estimate that strain changes as low as 10-6 can be measured using these devices. This method can be used with a wide variety of nanomechanical systems. Besides their utility as sensors, strain tuneable nanoresonators are interesting tools to study some of the most intriguing dynamical phenomena such as synchronization, mode coupling, internal resonance.
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