快力曲线中的隐藏动力学：瞬态阻尼与布朗运动驱动的接触共振
Hidden Information in Force Curves: Transient- and Brownian-Driven Dynamics
AI总结：
本研究利用新型干涉仪探测器，揭示快力曲线中瞬态阻尼和布朗运动驱动的接触共振，实现了高通量、高分辨率的机械对比映射，揭示了异质性和非重复行为。
摘要：
力-距离曲线（FCs）是原子力显微镜（AFM）中最直接的测量之一，但其信息内容常被滤波和准静态解释所减少。在这里，借助新的干涉仪探测器，我们展示了快速FCs本质上会激发短寿命的悬臂振荡，其瞬态频率和衰减编码局部刚度和耗散。通过在单曲线、单像素基础上分析这些动态，我们提取了时间局部的机械信息，而无需外部宽带激励或多步成像。我们开发了一个状态依赖的单模谐振子模型，该模型捕捉了snap-in激发、水合介导的耗散和接触刚度，在快速力映射过程中。高带宽力曲线数据的实验分析和数值模拟表明，在单个FC中会发生多个动态不同的相互作用区域。访问这些瞬态动态使高通量、高分辨率的机械对比映射成为可能，并揭示了异质性和非重复行为，这些行为在传统平均或传统检测方案中由于更高的噪声地板而被丢失。
英文摘要：
Force distance curves (FCs) are direct probes of tip sample interactions in atomic force microscopy, but their dynamic content is often suppressed by filtering, averaging and quasistatic analysis. Indeed, in the forty years since the invention of the AFM, this hidden dynamic signal has been largely ignored, with exceptions restricted to the large oscillations associated with relatively large adhesive separations (snap from contact) or to time averaged approaches that carry their own challenges. Using high bandwidth interferometric detection, we directly measure fast FCs, including short lived cantilever oscillations during snap in, contact and pull off. Two excitation mechanisms coexist: thermal fluctuations and transients generated by rapid changes in the tip sample boundary condition. Cycle resolved frequency and amplitude estimators provide time local observables of the evolving cantilever and sample system within single FCs, creating a pixel by pixel mechanical contrast channel that requires no external broadband excitation, resonant tracking or multi pass imaging. A state dependent harmonic oscillator model incorporating van der Waals attraction, hysteretic capillary bridge formation and rupture, hydration mediated damping and repulsive contact stiffness partitions each FC into five interaction regimes and reproduces the observed responses. In repulsive contact, frequency shifts yield stiffness maps consistent with contact-mechanics estimates, enabling high throughput stiffness mapping and localization of transient tip sample events from individual pixels. More broadly, this hitherto hidden signal may pave the way for new ways of studying and exploiting Brownian motion in a variety of systems, providing the capability to follow time resolved (non) Markovian and (non) ergodic dynamics mediated by the tip sample interaction, including single event dynamics.
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