Smart Gas Sensing and Actuation Using Multimode of a MOFs Coated Microbeam

Abstract

Smart sensing systems suffers complexity requiring interface circuits, microcontrollers, switches, and actuators to detect and sense, process the signal and take a decision, and trigger an action upon demand. This increases the device footprint and boosts significantly the power required to actuate the system. Here, we present a hybrid sensor and switch device, which is capable of accurately measuring gas concentration and perform switching when the concentration exceeds specific (safe) threshold. The device is based on a clamped-clamped microbeam coated with metalorganic frameworks (MOFs). Using the electrostatic harmonic voltage, we employ dynamic multi-modal actuation in which the microbeam is simultaneously excited at the first mode of vibration, near the pull-in band, and at the third mode. We demonstrate experimentally the effectiveness of this technique in measuring the concentration of water vapor and achieving switching when the concentration exceeds a threshold value. In contrast to a single mode operation, we show that employing multi-modal excitation enhances sensitivity, improves accuracy, and strengthen noise immunity.

Dynamic Behavior of T-beam Resonator With Repulsive Actuation

“…MEMS gas sensors employ a compliant element such as microcantilever beam [14,15]. Special coating is used for the microbeam to make it absorb certain molecules in the environment [16,17].…”

“…When the gas molecules adheres to the microbeam, the microbeam deflects and its resonance frequency changes. Either of these quantities (deflection or resonance frequency) could be measured [18,19,15] to determine the concentration of the target gas in the environment.…”

Dynamic behavior of T-beam resonator with repulsive actuation

“…Generally, mass sensor measurements depend greatly on absorption/adsorption of the targeted analytes on and into sensing layer [14,15]. When certain molecules adhere to the surface, the change in deflection (static mass sensing) or resonant frequencies (dynamic mass sensing) can be measured [16][17][18] to determine the concentration of the targeted analytes. Tiny microbeams with limited attaching surface can only accommodate small amount of molecules which generates limited deflection and shift in resonant frequencies.…”

A monolithic tunable symmetric bistable mechanism

“…Buckled and pre-shaped beams are widely used as bistable mechanisms at the small and large scale [1]. These mechanisms are employed in various applications in many sectors, including soft robotics [2], metamaterials [3], multistable positioning [4,5], resonators [6,7], actuators [8], gas sensing [9], pressure sensing [10], threshold sensing [11,12], logics [13], space applications [14], biomedical [15], and energy harvesting [16,17].…”