Surface Acoustic Wave (SAW) Resonators for Monitoring Conditioning Film Formation

Abstract

We propose surface acoustic wave (SAW) resonators as a complementary tool for conditioning film monitoring. Conditioning films are formed by adsorption of inorganic and organic substances on a substrate the moment this substrate comes into contact with a liquid phase. In the case of implant insertion, for instance, initial protein adsorption is required to start wound healing, but it will also trigger immune reactions leading to inflammatory responses. The control of the initial protein adsorption would allow to promote the healing process and to suppress adverse immune reactions. Methods to investigate these adsorption processes are available, but it remains difficult to translate measurement results into actual protein binding events. Biosensor transducers allow user-friendly investigation of protein adsorption on different surfaces. The combination of several transduction principles leads to complementary results, allowing a more comprehensive characterization of the adsorbing layer. We introduce SAW resonators as a novel complementary tool for time-resolved conditioning film monitoring. SAW resonators were coated with polymers. The adsorption of the plasma proteins human serum albumin (HSA) and fibrinogen onto the polymer-coated surfaces were monitored. Frequency results were compared with quartz crystal microbalance (QCM) sensor measurements, which confirmed the suitability of the SAW resonators for this application.

Miniaturized Hybrid Frequency Reader for Contactless Measurement Scenarios Using Resonant Surface Acoustic Wave Sensors

“…The first type can be described by taking a look at its schematic drawing in Figure 1. During a photolitographic process, different metallic structures are placed on the piezoelectric substrate like quartz (SiO 2 ) or lithiumniobate (LiNbO 3 ) [11,12,16]. incoming electromagnetic wave is transformed into a SAW which travels in this case to both sides in the direction of the second structure, the reflector gratings [16].…”

“…The first type can be described by taking a look at its schematic drawing in Figure 1 . During a photolitographic process, different metallic structures are placed on the piezoelectric substrate like quartz ( ) or lithiumniobate (LiNbO ) [ 11 , 12 , 16 ].…”

“…These sensors show several advantages of being small, contactlessly interrogable, passive and usable in harsh environments. Furthermore, besides the measurement of forces, they can be applied to determine several measurands like pressure, temperature or chemical mixture of liquids or gas, depending on the cut of the crystals of the piezoelectric material that is used as substrate for the sensors and the coating that is applied [ 10 , 11 , 12 ]. A changing measurand thus influences the resonance frequency of the sensor, which has to be determined, in order to calculate the actual measurand.…”

Bulk and Surface Acoustic Wave Biosensors for Milk Analysis

“…Furthermore, they are also classified as piezoelectric biosensors because of their operating principle (see Section 2.1 ). The best-known representatives of acoustic biosensor transducers are quartz crystal microbalances (QCMs) and surface acoustic wave (SAW) devices [ 15 , 16 , 17 , 18 , 19 , 20 ].…”

Single Interdigital Transducer Approach for Gravimetrical SAW Sensor Applications in Liquid Environments

“…Surface acoustic wave (SAW) devices with interdigitated microelectrodes serving as interdigital transducers (IDTs) are commonly used in the information technology industry as electronic filters in delay line or resonator configurations [ 1 , 2 ]. A remarkable characteristic of SAW sensors is their sensitivity to a number of physical parameters, e.g., temperature [ 3 , 4 ], humidity [ 5 , 6 ], mass [ 7 , 8 , 9 , 10 , 11 ], and especially for the detection of (bio)chemical binding events on surfaces [ 8 , 9 , 10 ]. So far, SAW sensors are commonly used in two configurations.…”