Surface acoustic wave sensors in the bioanalytical field: Recent trends and challenges

This is a comparison of the latest developments in the emerging field of surface acoustic wave (SAW) sensors. Progress has been made particularly with regard to (sub-) microstructure technology and material sciences. Improvements are displayed based on the impact on a new generation of SAW sensors working efficiently in liquid media, from modeling to the fabrication steps of the individual components. It is explained, which obstacles have to be overcome for applications to the bioanalytical field. SAW sensors are shown to be extremely useful for the analysis of both small and large molecules as well as whole cells interacting with an immobilized binding partner. The output signal gives information about the pure mass loading, intrinsic properties of bound materials, or viscoelastic effects like structural rearrangements. Different setups are shown that minimize the influence of physical bulk effects on the sensor signal, e.g. salt content and viscosity. The choice of materials which can be used for sensible surfaces are presented, enabling the development of completely new coupling chemistries. Finally, the advantages compared to other biosensor technologies are pointed out.