RF-MEMS load sensors with enhanced Q-factor and sensitivity in a suspended architecture

Abstract

In this paper, we present and demonstrate RF-MEMS load sensors designed and fabricated in a suspended architecture that increases their quality-factor (Q-factor), accompanied with an increased resonance frequency shift under load. The suspended architecture is obtained by removing silicon under the sensor. We compare two sensors that consist of 195 μm × 195 μm resonators, where all of the resonator features are of equal dimensions, but one’s substrate is partially removed (suspended architecture) and the other’s is not (planar architecture). The single suspended device has a resonance of 15.18 GHz with 102.06 Q-factor whereas the single planar device has the resonance at 15.01 GHz and an associated Q-factor of 93.81. For the single planar device, we measured a resonance frequency shift of 430 MHz with 3920 N of applied load, while we achieved a 780 MHz frequency shift in the single suspended device. In the planar triplet configuration (with three devices placed side by side on the same chip, with the two outmost ones serving as the receiver and the transmitter), we observed a 220 MHz frequency shift with 3920 N of applied load while we obtained a 340 MHz frequency shift in the suspended triplet device with 3920 N load applied. Thus, the single planar device exhibited a sensitivity level of 0.1097 MHz/N while the single suspended device led to an improved sensitivity of 0.1990 MHz/N. Similarly, with the planar triplet device having a sensitivity of 0.0561 MHz/N, the suspended triplet device yielded an enhanced sensitivity of 0.0867 MHz/N.

Implantable microelectromechanical sensors for diagnostic monitoring and post‐surgical prediction of bone fracture healing

“…Prior work by our group has undertaken an extensive series of experimental and analytical analyses that included resonance response frequency (RRF) computational models, prototype fabrication, and ex vivo simulations which clearly demonstrated the feasibility of using MEMS technology to telemetrically report on the mechanical environment of the plate‐sensor construct by monitoring shifts in the sensor's RRF …”

“…Prior work by our group has undertaken an extensive series of experimental and analytical analyses that included resonance response frequency (RRF) computational models, prototype fabrication, and ex vivo simulations which clearly demonstrated the feasibility of using MEMS technology to telemetrically report on the mechanical environment of the plate-sensor construct by monitoring shifts in the sensor's RRF. [10][11][12][13][14][15][16][17] There are two separate components to the bioMEMS system: (1) the bioMEMS sensor-implant construct (Fig. 1); and (2) the external excitation/receiving apparatus consisting of an antenna ( Fig.…”

Diagnostic prediction of ovine fracture healing outcomes via a novel multi-location direct electromagnetic coupling antenna

“…Ann Transl Med 2021 | https://dx.doi.org/10.21037/atm-21-1853 implantable microelectromechanical sensors (bioMEMS) capable of quantifying, via external antenna, temporal changes to the mechanical strain on implanted orthopaedic hardware (31,(41)(42)(43)(44)(45)(46)(47)(48)(49). In a previous study, temporally repeated bioMEMS measurements detected statistically significant differences in normal and aberrant bone healing in an ovine fracture model in as few as 21 days postfracture (31), and use of flexible bioMEMS enabled sensor application to most types of orthopaedic hardware (49).…”

Utilizing Multiple BioMEMS Sensors to Monitor Orthopaedic Strain and Predict Bone Fracture Healing

“…Our group has performed a series of experimental and analytical investigations of increasing complexity upon MEMS‐based telemetric measurements of local fracture mechanics by observing shifts in the sensor's resonance response frequency (RRF) using computational models, prototype fabrication, ex vivo simulations, and in vivo animal models . The current system is composed of a multi‐sensor fsBioMEMS sensor‐implant construct and an external excitation/receiving apparatus consisting of a multi‐antenna array and a network analyzer (Fig.…”

“…There is a current lack of non‐invasive diagnostic measures to determine callus strength, a metric which is crucial in diagnosing the state of bone healing and the patient's ability to bear weight . Previous studies have shown success in the use of sensors to telemetrically quantify construct mechanical environment . Use of a single wireless, biocompatible, microelectromechanical system (BioMEMS) sensor has previously utilized the bone‐implant load sharing principle to successfully detect statistically significant differences in normal and delayed healing in an ovine animal model as early as 21 days post‐fracture .…”