研究目的
To design high-performance harmonic probes with tailored resonant modes for multifrequency atomic force microscopy, focusing on matching higher-order resonance frequencies to integer multiples of the fundamental frequency, increasing the effective tip slope for improved sensitivity, and maximizing the fundamental frequency for faster scanning speed.
研究成果
The structural optimization method effectively designs harmonic probes that meet the requirements of matching higher harmonic frequencies to resonance frequencies, increasing tip slope for sensitivity, and maximizing fundamental frequency for speed. Experimental validation shows good agreement with design objectives, demonstrating the method's effectiveness for improving multifrequency atomic force microscopy performance.
研究不足
The study is limited to flexural vibration modes; torsional modes are not considered. Fabrication and measurement errors may cause discrepancies between design and actual results. The method may not be easily extended to arbitrary frequency ratios significantly different from the original case. Batch fabrication by lithography and robust design under uncertainty are noted for future study.
1：Experimental Design and Method Selection:
A structural optimization technique is used to design cantilever probes. The probe is modeled as a three-layer symmetrical cantilever beam, and its width profile is optimized using a gradient-based method to achieve desired frequency ratios and mode shapes. Finite element analysis (FEA) is employed for simulation.
2：Sample Selection and Data Sources:
A commercial AFM silicon probe (240AC-NA; Opus) is used as the starting point. Its properties include length 240 μm, width 40 μm, thickness 2.6 μm, density 2330 kg/m3, and Young's modulus 169 GPa.
3：6 μm, density 2330 kg/m3, and Young's modulus 169 GPa.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment includes focused ion beam (FIB) milling system (Helios NanoLab G3 CX; FEI), atomic force microscope (AFM) (MultiMode 8; Bruker), scanning electron microscope (SEM), and FEA software (ANSYS). Materials include silicon for the probe.
4：Experimental Procedures and Operational Workflow:
The optimization is performed with 400 iterations. The optimized probe is fabricated using FIB milling with parameters: 30 kV ion beam voltage and 2.5 nA ion beam current. The fabricated probe is characterized using SEM and AFM to measure resonance frequencies and mode shapes.
5：5 nA ion beam current. The fabricated probe is characterized using SEM and AFM to measure resonance frequencies and mode shapes.
Data Analysis Methods:
5. Data Analysis Methods: Resonance frequencies are measured using AFM. Mode shapes are analyzed using FEA (ANSYS). Modal assurance criterion (MAC) is used to quantify similarity between actual and target mode shapes.
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