MEMS Nanoindenter Comb Drive for Accurate Force Measurement
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Solution Overview
Problem
Conventional nanoindentation technologies face challenges such as inaccurate penetration depth measurement due to piezo characteristics, limited displacement sensitivity, environmental sensitivity in displacement sensing, inappropriate spring design for nanoindentation, electrical noise from conductive tips, and vulnerability to contamination and damage in small-scale applications like in-situ TEM testing.
Innovation Solution
A MEMS-based nanoindenter transducer with a micromachined comb drive for actuation and sensing, featuring differential capacitive sensing, optimized spring design for directional stiffness, electrical isolation of the indenter tip, and protective packaging to prevent contamination and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If piezo actuation is used for indentation force application, then force can be applied to the sample, but penetration depth measurement becomes inaccurate due to piezo characteristics such as creep, hysteresis, and nonlinearity
Solution Approach 1:
The patent introduces a compliant beam as an intermediary element between the piezo actuator and the indenter tip. This compliant beam mechanically couples the piezo's motion to the indenter while providing a known spring constant, allowing the system to measure penetration depth through force equilibrium calculations rather than direct piezo displacement measurement, thereby eliminating errors from piezo creep, hysteresis, and nonlinearity
Solution Approach 2:
The patent replaces direct piezo displacement measurement with a mechanical spring-based force measurement system. By using the compliant beam's known spring constant and measuring the reaction force, the system substitutes the problematic piezo displacement sensing with a mechanical measurement approach that is not susceptible to piezo characteristics
2Ease of operation
If conventional capacitive sensing with single electrode pair is used, then displacement sensing can be implemented, but sensitivity is limited and environmental changes cause errors
Solution Approach 1:
The patent divides the sensing system into multiple independent capacitive sensing elements arranged in a differential configuration. Instead of using a single electrode pair, the system employs multiple capacitor pairs that can be combined to create a differential measurement, which cancels out environmental effects and increases sensitivity
3Volume of moving object
If small-scale transducer is used for in-situ TEM testing, then space constraints are satisfied, but the transducer becomes vulnerable to contamination and damage
Solution Approach 1:
The patent implements a nested protective structure where the indenter tip is housed within a protective chamber or housing that can be sealed. This nested design allows the transducer components to be protected from contamination and damage while maintaining the compact size required for TEM applications, as the protection structures are integrated within the existing form factor
4Adaptability or versatility
If conductive tip is used for nanoindentation, then electrical measurement can be performed, but electrical noise is generated
Solution Approach 1:
The patent extracts or separates the electrical measurement function from the mechanical indenter tip. By using a non-conductive tip for mechanical indentation while employing separate capacitive sensing elements for electrical measurements, the system eliminates the electrical noise generated by conductive tips while maintaining the capability for electrical measurements through the isolated capacitive sensing 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 MEMS nanoindenter transducer provides accurate and sensitive force and displacement measurements, reduces errors in mechanical property estimation, enhances sensitivity and bandwidth, and ensures reliable operation in small-scale applications like in-situ TEM testing.
Implementation Method 1
A well designed nanoindenter transducer can improve many aspects of the nanoindenter performance... The present disclosure describes embodiments of a micro-electro-mechanical system (MEMS) transducer for nanoindentation applications. According to embodiments described herein, the MEMS transducer employs a micromachined comb drive for actuation and sensing.
Implementation Method 2
Some conventional MEMS based nanomechanical testers utilize capacitance change for displacement sensing... The sensor includes an actuator which can drive the movable parts by changing an applied voltage. The displacement of the further movable part is detected by an admittance detector as a change of an admittance.
Data Source
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AI summary
A system and method of measuring an interaction force is disclosed. One embodiment includes providing a method of measuring an interaction force including providing a microelectromechanical transducer. The transducer includes a body, a probe moveable relative to the body, and a micromachined comb drive. The micromachined comb drive includes a differential capacitive displacement sensor to provide a sensor output signal representative of an interaction force on the probe. The probe is moved relative to a sample surface. An interaction force is determined between the probe and the sample surface using the sensor output, as the probe is moved relative to the sample surface.