Approaches to Increasing Surface Stress for Improving Signal-to-Noise Ratio of Microcantilever Sensors

Abstract

SummaryMicrocantilever sensor technology has been steadily growing for the last fifteen years. While we have gained a great amount of knowledge in microcantilever bending due to surface stress changes, which is a unique property of microcantilever sensors, we are still in the early stages of understanding the fundamental surface chemistries of surface-stress-based microcantilever sensors. In general, increasing surface stress, which is caused by interactions on the microcantilever surfaces, would improve the S/N ratio, and subsequently the sensitivity and reliability of microcantilever sensors. In this review, we will summarize: A) the conditions under which a large surface stress can readily be attained, and B) the strategies to increase surface stress in case a large surface stress can not readily be reached. We will also discuss our perspectives on microcantilever sensors based on surface stress changes.

Microcantilevers Modified with Ferrocene-Terminated Self-Assembled Monolayers: Effect of Molecular Structure and Electrolyte Anion on the Redox-Induced Surface Stress

“…A marked difference in the FcC 11 SAu-modified microcantilever response is evident with the hydrophilic NO 3 -and Fanions. Significant decreases in the anodic peak currents (14% for NO 3 -and 45% for F -) and Δσ FcfFc þ (24% for NO 3 -and 43% for F -) are observed over the three potential cycles shown in Figure 3d,e. Moreover, the cantilevers do not return to their initial zero-stress (open circuit) positions at the end of the first oxidation-reduction cycle.…”

“…The Δσ FcfFc þ values measured during the second anodic scan (where the baselines before and after the oxidation-reduction cycle are the same) are -0.11 ( 0.03 N m -1 and -0.06 ( 0.03 N m -1 in the presence of NO 3 -and F -, respectively. For the oxidation of SAM-bound ferrocenes in NO 3 -and F -, deducing the origin(s) of the surface stress is more complicated. Coulomb repulsion between neighboring ferrocenium moieties (i.e., less effective ion pairing), potential-induced ion and solvent penetration into the SAM, anion adsorption to the positively charged, underlying gold surface, and a destabilization of the SAM are possible contributors.…”

Nanomechanical Cantilever-Based Sensor: An Efficient Tool to Measure the Binding Between the Herbicide Mesotrione and 4-Hydroxyphenylpyruvate Dioxygenase

“…True de-°e ction constitutes movement of the cantilever that is attributed to surface stress resulting from intermolecular binding reactions. 35,36 We quali¯ed our measurements as real de°ections, except in the case of positive measurements for the biosensor; these were established after comparison with the respective control PBS injections. Observed response times ranged from 10 to 15 min, and constituted the minimal time necessary for the de°ection system to reach equilibrium and stabilization.…”

Hyper-branch sensing polymer batch self-assembled on resonant micro-cantilevers with a coupling-reaction route

“…Among various types of gas sensors, resonant micro-cantilevers are advantageous in ultra-high sensitivity, miniaturized size and facile integration with signalacquisition circuit [10][11][12][13][14][15][16][17][18][19]. For chemical sensing functionalization, sensing material with high specific surface area should be integrated onto the micro-gravimetric transducer of the resonant micro-cantilever.…”