Electrical and Optical Characterization of SAW Sensors Coated with Parylene C and Their Analysis Using the Coupling-of-Modes (COM) Theory

Abstract

In this paper, we present how complementary characterization techniques, such as electrical measurements with a vector network analyzer (VNA), optical measurements with a laser Doppler vibrometer (LDV), and numerical simulations with the finite element method, coupled with spectral domain analysis (FEMSDA), allow us to independently access different properties of a SAW device and fully characterize its operation using the coupling-of-modes theory (COM). A set of chemical SAW sensors coated with parylene C layers of different thicknesses (1, 1.5, and 2 µm) and an uncoated sensor were used as test samples. The sensors represent dual-channel electroacoustic delay lines operating in the vicinity of 77 MHz. The IDTs consist of split aluminum electrodes deposited on a AT-cut quartz substrate. The thickness-dependent influence of the parylene C layer was observed on the operating frequency (SAW velocity), static capacitance, attenuation, crosstalk, and reflection coefficient. COM parameters were reported for the four cases considered; measured and simulated data show good agreement. The presented approach is suitable for the design, characterization, and validation of polymer film-coated SAW sensors.

Exploring Interactions and Properties of the Sodium Carboxymethyl Cellulose–Chitosan Biopolymer Complex

“…In recent years, great efforts have been made to develop biocompatible and biodegradable devices for various applications. [1][2][3][4][5][6] With the increasing environmental awareness among the people, [7,8] more ecofriendly, [9] renewable, and biodegradable materials are being produced using cost-effective techniques. [10,11] Thus, pharmaceutical technology has focused on the development of release biodegrabable systems, [12] such as gels, that are capable of controlling the release of the drug to exactly where it is absorbed or acts at the desired rate.…”