Figure 2.

(a) Change in Au/SiN_x cantilever deflection as a function of time for three different experiments: (i) exposure to 0.1 M PB; (ii) exposure to unthiolated probe ssDNA; (iii) exposure to probe ssDNA thiolated at the 5′ end. Concentrations of unthiolated and single-end thiolated ssDNAs were all 50 ng/μl or approximately 3.2 μM. Unthiolated ssDNA and pure PB solutions did not produce any significant deflection. Inset shows the steady-state cantilever deflection as a function of length of the probe ssDNA thiolated. Results indicate that immobilization of probe ssDNA produces compressive stress bending the cantilever down. (b) Steady-state cantilever deflections caused by immobilization of ssDNA (sequence K-30) at different PB concentrations.