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Resolving Fine Electromechanical Structure of Collagen Fibrils via Sequential Excitation Piezoresponse Force Microscopy
摘要： Collagen is the main protein in extracellular matrix that is found in many connective tissues, and it exhibits piezoelectricity that is expected to correlate with its hierarchical microstructure. Resolving fine electromechanical structure of collagen, however, is challenging, due to its weak piezoresponse, rough topography, and microstructural hierarchy. Here we adopt the newly developed sequential excitation (SE) strategy in combination with piezoresponse force microscopy (PFM) to overcome these difficulties. It excites the local electromechanical response of collagen via a sequence of distinct frequencies, minimizing crosstalk with topography, followed by principal component analysis (PCA) to remove the background noise and simple harmonic oscillator (SHO) model for physical analysis and data reconstruction. These enable us to acquire high fidelity mappings of fine electromechanical response at the nanoscale that correlate with the gap and overlap domains of collagen fibrils, which show substantial improvement over conventional PFM techniques. It also embodies the spirit of big data atomic force microscopy (AFM) that can be readily extended into other applications with targeted data acquisition.
关键词： Principal component analysis,Sequential excitation,Simple harmonic oscillator model,Piezoresponse force microscopy,Collagen
更新于2025-09-19 17:15:36
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Impact of the Coulomb Potential and the Electrostatic Potential on the Eigen-Frequencies of the Coupled Plasmons
摘要： In this paper, a coupled oscillator model is employed to describe the eigen-frequencies of the coupled plasmons, which are dominated by the coupled coefficient and the frequency offset defined by us. From this, we present a novel physical model to describe the influence of the Coulomb potential and the electrostatic potential (CPEP) on the coupled coefficient and the frequency offset. Based on the finite element method, we simulate numerically the evolution of the absorption spectra of the microstructure unit composed of a simply metal nanostructure. The simulated results show that two resonant absorption peaks are asymmetrical with the change of the coupling distance between the nano-elements. With the CPEP model, we not only explain successfully the asymmetrical behaviors of the peaks values of the absorption spectra with the change of the coupling distance but also obtain the resonant frequencies for different plasmons. The absorption spectra are simulated by the harmonic oscillator model, in which their calculated parameters originate from the CPEP model, and the results are very well association with those of the numerical simulation.
关键词： Eigen-frequencies,Harmonic oscillator model,Frequency offset,Coulomb potential and electrostatic potential
更新于2025-09-11 14:15:04