Research Activities

Thin Film Lamb Wave Resonators in Frequency Control and Sensing Applications

SAW Phononic Bandgap Grating (PGB) Resonant Devices

The development of the Lamb wave resonator (LWR) technology was initiated in 2003-2004 with the demonstration of the first thin film based resonator employing the lowest order symmetric Lamb wave (S0) [APL2005]. Currently the S0 mode in AlN membranes has mostly been explored because of its unique combination of extremely high velocity, low dispersion and moderate piezoelectric coupling. Recently the XBAR utilizing the A1 Lamb mode in Z-Y LiNbO3 and 120Y-X LiNbO3 thin membranes have been developed in view of designing wide band filters in the 3GHz-7GHz range. The first prototype of a 5GHz XBAR filter has been presented at [2019 IUS] in Glasgow.

IC-compatible Microacoustic Sensors

Another area of research is the development of thin film electro-acoustic sensors. Among the major advantages of the TEA sensor technology are its IC compatibility, low cost, small dimensions and most of all its extreme sensitivity towards pressure, mass loading, viscosity, etc. A variety of physical, chemical and bio-chemical sensors are currently under development. The emphasis is on the design of high Q, temperature compensated sensors with improved resolution. Few types of sensor elements have been developed withi this frame:

- Highly sensitive FBAR Bio-sensors

- Highly sensitive LWR pressure and Gas sensors

More specifically thin film LWR pressure sensors are among the most sensitive electroacoustic components subjected to ambient pressures. Resolutions down to 1Pa - range are feasible [JMM 2011].

Development of the Surface Acoustic Resonance (SAR) Technique for Bio-Sensing Applications

Sensors capable of in-liquid operation are of primary importance not only for biosensors applications, but also for liquid monitoring. Surface acoustic waves (SAW) have been employed for long time in various in-liquid sensors at relatively high frequencies. Unlike their QCM counterparts, SAW in-liquid sensors employ delay-line topology. Here, for the first time, we propose and develop a new concept for building a SAW in-liquid sensor employing surface acoustic wave resonance (SAR) in a one-port configuration. To demonstrate its utility, SAR technological platforms embedded in a polydimethylsiloxane (PDMS) microfluidic device are fabricated and characterized. Designs with suppressed spurious content are identified. We address the straightforward ability to integrate the SAR device with Impedance spectroscopy and Optical microscopy measurements for Lab-on-Chip Bio-sensors with improved specificity and selectivity. In comparison to a SAW delay-line topology, the SAR concept features comparable sensitivity, while offering better electrical performance and smaller size. This concept is patented with all details: A. Jesorka, K. Kustanovich, and V. Yantchev, "A Surface Acoustic Wave Resonant Sensor," (in English), Swedish Patent and Registration Office, Patent no. 200697SE, May 2017.

In this project, 2D grating patterns technologically compatible with the SAW planar technology are studied in view of designing resonators with significantly improved waveguiding and thus reduced losses from wave diffraction away from the active resonant cavity. The phonic bandgap grating belong to the class of surface phononic crystals, with the advantage to enable easy co-inetgartion with piezoelectric substrates. COMSOL FEM studies prior to the experimental verification proved that omnidirectional SAW bandgaps are technologically feasible. First experimental results have been published in 2014. Such an approach could have a significant impact over the SAW technology in near future.

Utilization and Development of Design Models

- Coupling of Modes Theory (COM)

- 1D BAW models (Christofel Equations, Mason Model, Nowotny-Benes Model, BVD )

- Modal analysis (Bandgap Characteristics of SAW, BAW and Plate modes)

- COMSOL FEM simulations of 1D, 2D and 3D Micro-mechanical structures with correct interpretation of the underlying physics.

The electroacoustics (EA) make use of advanced methods for thin film deposition along with micromachining techniques for the fabrication of IC compatible RF components. The development of optimized EA devices for frequency control and sensors applications requires the use of advanced design tools. The utilization as well as the development of design tools and physical models is of crucial importance for the quality of our research. We utilized the Nowotny-Benes one dimensional model towards the design of FBAR and SMR structures for both frequency control and sensing applications. A variety of theoretical models have been developed for the design of structures utilizing fast laterally propagating modes.The Coupling-of-Modes approach complemented by modal analysis based on the Floquet-Bloch theorem as well as the Green's function formalism have been successfully employed for the development and optimization of various resonant components. In recent years we extended our scope to Finite Element Methods usingCOMSOL Multiphysics. 2D and 3D analytical models are being succesfully developed for the design of SAW, FBAR and LWR components.

3D FEM model on Langasite

Analysis and Optimization of Aperture Effects in LSAW, TC-SAW, TF-SAW Resonators for RF Filters

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