An ultra-high sensitivity Surface Acoustic Wave (SAW) biosensor operated in high order mode for DNA sequences detection is proposed. Nanoscale interdigitals are fabricated on LiNbO3 substrate to achieve a high quality factor of over 4000 at about 6.4GHz. The biosensor shows an excellent linear response to the target DNA in the range of 1ng/ml to 1μg/ml and the difference of hybridized single DNA base can be distinguished. An effective DNA immobilization increases the frequency shifts greatly, which also contributes to the high sensitivity of 6.7×10-16g/cm2/Hz.
