The use of a polar co-monomer (HEMA), which provides the stability of the nanospheres in water, and a hydrophobic polymer (PA), allows to produce a co-polymer with charged surface and hydroxyl groups on the particles surface. These properties of the nanospheres improve their adhesion on substrates, the high order of wide domains of CIM coating and the capability to bind polar molecules. The resulting chemical sensor has been tested at different relative humidity values.Figure 5.Chemical structure of P(PA/HEMA) (a). Morphology of the nanostructured polymer film used as CIM as seen at SEM (b).To implement the sensing unit, different masses of an aqueous solution of the nano-structured polymer P(PA/HEMA) have been deposited on the four channels of the MQCM and on four single QCM by casting technique.
Once the solvent has evaporated, a thin film of the material has remained on the substrate. According to Sau
Each biosensor has two primary components: bio-recognition element and transducer. The bio-recognition element, such as antibody and phage, is highly specific to the target species [1-4]. The reaction between the target species and the bio-recognition unit would result in some changes in the physical/chemical properties of the recognition unit. These changes are measured using a transducer. Different types of transducers have been developed and extensively investigated in recent years. One important type of the transducer is the acoustic wave (AW) device [5-14], which is an acoustic resonator and works as a mass sensor.
That is, the reaction between the bio-recognition component and the target species results in a change AV-951 in the mass load of the transducer/resonator, which shifts the resonance frequency. Thus, by monitoring the resonance frequency of the AW device, the reaction between the bio-recognition unit and the target species, such as captured bacterium cells by antibody/phage, can be determined. An AW device as a transducer used in biosensors is characterized using two critical parameters: mass sensitivity (Sm) and quality merit factor (or Q value) [9, 12, 14-16]. The mass sensitivity is defined as the shift in resonance frequency due to the attachment of a unit mass, while the Q value reflects the mechanical loss of the devices and characterizes the sharpness of the resonance peak in the amplitude/phase versus frequency plot.
A higher Sm means a more sensitive device, while a higher Q value represents a capability to determine a smaller change in resonance frequency (i.e. a higher resolution in determining resonance frequency). Therefore, it is highly desirable for an AW device to have a higher Sm and a larger Q value. Among all AW devices, micro/nano-cantilever exhibits extremely high sensitivity primarily due to its small mass [17-20]. For example, the detection of a mass as small as 10-18 g using cantilever has been demonstrated.