We developed a surface acoustic wave (SAW) sensor system for detection of the immobilization and hybridization of DNA molecules. The sensor consists of twin SAW delay line oscillators (sensing channel and reference channel) fabricated on 36° rotated Y-cut X-propagation LiTaO3 piezoelectric single crystals. Center frequency of the SAW oscillators is 200 MHz. The relative change in the frequency of the two oscillators was monitored to detect the immobilization of a probe DNA with thiol group on an Au coated delay line and the hybridization between a target DNA and the probe DNA. The target solution was continuously flowing over the probe DNA layer via micro-fluidic channels made of polyimide tubes. The sensitivity of the sensor was as high as 136 pg/(ml·Hz). In addition to the inherent advantage of being label-free, the SAW DNA sensor in this paper has promising practical applicability in terms of the sensitivity.

We developed a surface acoustic wave (SAW) sensor system for detection of the immobilization and hybridization of DNA (deoxyribonucleic acid) molecules. The experiments of DNA immobilization and hybridization were performed with 15-mer oligonucleotides (probe and complementary target DNA). The sensor consists of twin SAW delay line oscillators (sensing channel and reference channel) fabricated on 36˚ rotated Y-cut X-propagation LiTaO 3 piezoelectric single crystals. Center frequency of the SAW oscillators is 200 MHz. The relative change in the frequency of the two oscillators was monitored to detect the immobilization of a probe DNA with thiol group on an Au coated delay line of the SAW device and the hybridization between a target DNA and the immobilized probe DNA in pH 7.4 PBS (phosphate buffered saline) solution. The target solution was continuously flowing over the probe DNA layer via micro-fluidic channels made of polyimide tubes. The exact amount of the flow was controlled by digital pumps operated by LabView® software.The sensitivity of the was as high as 136 pg/ml/Hz. It has been normally considered that a SAW sensor is inferior in sensitivity to optical systems in detecting DNA molecules. However, in addition to the inherent advantage of being label-free, the SAW DNA sensor was confirmed by the results in this paper to have promising practical applicability in terms of the sensitivity.

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