Atomic Force Microscopy Using Electromagnetic Coil Induction
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Solution Overview
Problem
Current atomic force microscopy (AFM) techniques face limitations in imaging soft or biological samples due to damage from applied bias voltage and require stiff cantilevers, leading to poor resolution and sensitivity, especially when measuring magnetic and ferroelectric properties.
Innovation Solution
An AFM system with a cantilever and electromagnetic coil that generates a time-varying magnetic field, allowing for imaging of various sample properties without bias voltage and using softer cantilevers, enabling higher sensitivity and resolution, particularly for electrical, dielectric, and magnetic property measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If bias voltage is applied between conductive tip and sample to measure electric and dielectric properties, then measurement capability is improved, but sample damage and property alteration occur
Solution Approach 1:
The patent replaces the electrical measurement system (bias voltage and conductive tip) with a magnetic measurement system. An electromagnetic coil generates a time-varying magnetic field that induces currents within the sample material, and a magnetic tip detects these induced currents through magnetic field interactions. This substitution eliminates direct electrical contact with the sample, preventing sample damage and property alteration while maintaining measurement capability for electric and dielectric properties.
Solution Approach 2:
The patent introduces a time-varying magnetic field as an intermediary between the measurement system and the sample. The electromagnetic coil generates the magnetic field, which penetrates the sample and induces currents without requiring direct electrical contact. The magnetic tip then detects the induced currents through magnetic field interactions. This intermediary approach allows measurement of electrical properties without applying bias voltage directly to the sample, thus avoiding sample damage.
2Reliability
If stiff cantilever with spring constant of 2-40 N/m is used in MFM, then magnetic property measurement is enabled, but resolution and sensitivity deteriorate
Solution Approach 1:
The patent changes the key parameter of cantilever stiffness from high (2-40 N/m in conventional MFM) to low (softer cantilever). This parameter change enables the cantilever to be more responsive to minor changes in magnetic interactions, thereby improving resolution and sensitivity. The softer cantilever can detect smaller forces while still maintaining the capability to measure magnetic properties through the time-varying magnetic field approach.
Solution Approach 2:
The patent employs dynamic operation where the electromagnetic coil generates a time-varying magnetic field that oscillates at a predetermined frequency. The cantilever is driven to vibrate at this frequency, and the system operates in a dynamic regime rather than static. This dynamic approach enhances the sensitivity of the measurement by utilizing the oscillatory motion of the cantilever and the time-varying nature of the magnetic field, allowing softer cantilevers to achieve high measurement precision.
3Measurement precision
If increasing magnetic field surrounding the tip is applied to increase resolution, then image quality improves, but sample magnetization is affected
Solution Approach 1:
The patent uses periodic action by generating a time-varying magnetic field that oscillates at a predetermined frequency rather than applying a static or continuously increasing magnetic field. The electromagnetic coil is excited by an AC signal, creating an oscillating magnetic field that induces currents in the sample. This periodic approach allows the system to achieve high resolution through the dynamic interaction between the oscillating field and the sample, while avoiding the continuous strong magnetic field that would cause sample magnetization.
Solution Approach 2:
The patent substitutes the conventional approach of using a strong static magnetic field from a magnetic tip with a dynamic electromagnetic induction approach. Instead of relying on a permanent magnetic field from the tip, the system uses an electromagnetic coil to generate a time-varying magnetic field that induces currents in the sample, which are then detected by a non-magnetic or weakly magnetic tip. This substitution eliminates the need for strong magnetic fields that would affect sample magnetization while maintaining high resolution through the induced current detection mechanism.
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
The system provides high-resolution imaging of multiple sample properties with minimal alteration, improving sensitivity and reducing equipment costs, and is capable of imaging soft and biological materials without damaging them.
Implementation Method 1
an electromagnetic coil coupled to the generator to receive the signal and to excite the electromagnetic coil to create a time-varying magnetic field, wherein the time-varying magnetic field creates a secondary magnetic field within the sample material
Implementation Method 2
A laser beam is focused on a portion of the cantilever during scanning, and a photodiode detector or other suitable detector collects the reflected light in order to detect minute deflections of the cantilever
Data Source
AI summary
An atomic force microscope (AFM) system capable of imaging multiple physical properties of a sample material at the nanoscale level. The system provides an apparatus and method for imaging physical properties using an electromagnetic coil placed under the sample. Excitation of the coil creates currents in the sample, which may be used to image a topography of the sample, a physical property of the sample, or both.