Figure 5.

Bending response as a function of time for AChBP-coated microcantilevers prepared using methods A and B on exposure to 1 × 10⁻⁵ M acetylcholine solution. The Langmuir adsorption model was used to describe the absorption of acetylcholine on the protein-covered surface. The rate of formation of a fraction of a monolayer, θ, is proportional to the concentration of acetylcholine in solution and to the fraction of the surface remaining free of sorbant, 1 − θ. Thus, the cantilever bending vs time is described by²⁴ δ ∝ 1 − exp(−kt), where δ is the surface stress, k is the reaction rate, and t is the time. k was calculated to be 1.5 and 0.45 min⁻¹ for methods A and B, respectively, using a nonlinear curve-fitting method to fit the observed experimental data. The fitted curve was shown by the dashed line.