Contact Acoustic Microscope Motion Compensation for Low-Damage Scanning
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Solution Overview
Problem
Existing acoustic microscopy methods cause significant damage to samples due to direct mechanical contact or require inefficient oscillating motions, leading to reduced measurement efficiency.
Innovation Solution
A contact acoustic microscope with a scanning head, tip actuator, and motion compensator that minimizes tip displacement relative to the sample, allowing continuous scanning with a large contact surface and reduced mechanical load, using flexible elements and interface layers to maintain stable contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the probe performs continuous scanning in permanent contact with the sample surface, then the measurement efficiency is improved, but the sample is significantly damaged
Solution Approach 1:
The probe tip is made dynamically oscillating in the tapping mode, transitioning from static continuous contact to dynamic periodic contact. This allows the tip to rapidly tap against the sample surface at high frequency while maintaining average contact forces low enough to prevent damage, thereby enabling continuous scanning without sample destruction
Solution Approach 2:
The probe executes periodic oscillatory motions during scanning, where the tip repeatedly contacts and releases from the sample surface in a rhythmic pattern. This periodic action distributes the mechanical stress over time, allowing continuous measurement coverage while preventing cumulative damage that would occur with static permanent contact
2Object-affected harmful factors
If the probe oscillates in tapping mode to reduce sample damage, then the sample damage is significantly mitigated, but the measurement efficiency is significantly reduced due to limited contact time
Solution Approach 1:
The probe tip is driven to vibrate at high frequency during the scanning process. This mechanical vibration creates rapid oscillations that allow the tip to maintain contact with the sample surface for extended periods within each oscillation cycle, thereby increasing the effective measurement time while keeping peak contact forces low enough to avoid damage
Solution Approach 2:
The oscillation frequency and amplitude of the probe tip are dynamically adjusted during scanning to optimize the balance between contact time and contact force. By changing these parameters, the system maximizes the duration of sufficient contact area for acoustic signal transfer while ensuring that the mechanical stress remains below damage thresholds
3Object-affected harmful factors
If the tip is alternatingly brought into contact with the sample in point to point approach, then the sample damage is significantly mitigated, but the measurement efficiency is even lower due to required waiting time for oscillation dampening
Solution Approach 1:
The probe maintains continuous contact with the sample surface throughout the scanning process, eliminating the need to retract and wait for oscillation dampening between measurement points. The continuous oscillatory motion ensures that acoustic signal transfer occurs without interruption, achieving both continuous scanning capability and minimal sample damage simultaneously
4Reliability
If a liquid layer is used on the sample surface for acoustic coupling, then the acoustic signal transfer is improved, but the liquid layer requires additional handling and may interfere with certain measurements
Solution Approach 1:
The system replaces the liquid coupling medium with direct mechanical contact between the probe tip and sample surface. By establishing solid-to-solid contact through the oscillating tip, the system achieves effective acoustic signal transfer without requiring liquid layers, thereby eliminating the complexity of liquid handling and potential interference with measurements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables high-efficiency acoustic measurements with reduced sample damage by maintaining a large contact surface and minimizing mechanical oscillations, optimizing acoustic signal transfer while reducing friction and mechanical stress.
Implementation Method 1
a piezo on top of a delay line
Implementation Method 2
a piezo on top of a delay line
Data Source
Figure 1
Figure 2~2B
Figure 3A~3C
AI summary
A contact acoustic microscope (1) is disclosed that comprises a scanning head (20) with a tip (21), a scanning actuator (31), a tip actuator (4), a high frequency signal source (5), a transducer (6) coupled thereto, an acoustic sensor (6), a signal processor (10) and an actuator controller (11). The scanning actuator (31) laterally displaces the scanning head (20) relative to a sample (S) along a scanning path (P) in a scanning plane (x,y). The tip actuator (4) oscillates the tip in a direction (z) transverse to the scanning plane to therewith provide for a time-dependent tip-sample contact surface (A(t)). The high frequency signal source (5) and the transducer (6) coupled thereto generate an acoustic signal that is provided through the tip of the probe to the sample. The acoustic sensor (6) provides a sense signal (Ssns) indicative for an acoustic signal received from the sample via the tip, which is processed by the signal processor (10) to render subsurface information about the sample. The actuator controller (11) controls the scanning actuator (3) and the tip actuator (4). The motion compensator compensates a lateral movement of the scanning head to minimize a displacement of the tip (2) relative to the sample (S) while the tip (21) is in contact with the sample (S).