Abstract

Thin Film Bulk Acoustic Resonator Biosensors with Femtogram Mass Sensitivity

Andrew Flewitt, Reader, Cambridge University

Over the last decade there has been an increased interest in developing sensitive chemical and biological sensors for early diagnosis of diseases and genetic disorders through detection of associated molecules such as DNA, proteins and peptide aptamers. Film bulk acoustic wave resonators (FBARs) have been shown to improve the sensitivity and detection limitation compared to other existing technologies, with the possibility of integrating an array of FBARs into existing electronics for control and data processing. However to date the usefulness of these sensors is limited to laboratories where environmental conditions, that are known to have an effect on the response of the sensors, can be tightly controlled. In this work, novel FBARs exhibiting two modes of resonance are presented. These resonance modes have been designed to exhibit opposite reactions to mass loadings and temperature variations, hence one single device holds information on whether any observed response is due to mass load, temperature change, or a combination of both, avoiding undesirable false responses. In addition, the utilisation of some nanomaterials such as carbon nanotubes as electrodes for the devices will be shown to increase significantly the mass sensitivity due to the greater surface to volume ratio of these materials compared to standard metallic electrodes. In particular, we have fabricated FBARs capable of detecting temperature variations (with sensitivities of ±0.01°C) in parallel with mass loadings (with sensitivities of ±10–15g), and have demonstrated the suitability of these sensors for the detection of a number of targeted biological systems such as antigen/antibodies, proteins and DNA.