Figure 3.

(a) Changes in Au-Si cantilever deflection caused by hybridization of a probe ssDNA (sequence K-20 at 50 ng/μl or 8 μM concentration) in the distal end with complementary target ssDNA of different lengths—20 nt, 15 nt, 10 nt, and 9 nt (40 ng/μl or 3- to 6-μM concentration). Also shown is the absence of cantilever deflection for a noncomplementary target ssDNA (sequence NC20). The data clearly suggest that differences in nanomechanical motion caused by a 1-nt difference in length can be observed. (b) Steady-state changes in cantilever deflection for hybridization of 30-nt-long ssDNA (sequences K-30 and K′-30) at different PB concentrations. Note that immobilization of probe ssDNA (sequence K-30) were at the same PB concentration (0.1 M) as the hybridization reaction for both a and b.