Capacitive Force Sensor for Sub-millinewton Material Characterization

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Solution Overview

Problem

Conventional systems for mechanical characterization of materials and biological samples in the sub-millinewton force range are limited by their inability to directly measure both force and deformation, often require extensive sample preparation for specific orientations, and rely on image processing for position information, making them unsuitable for diverse sample types and applications.

Innovation Solution

A system incorporating capacitive force sensors integrated with multi-axis micromanipulators and microscopes, allowing for adjustable sensing directions, simultaneous measurement of position and deformation using encoders, and featuring compact, high-resolution force sensing capabilities, enabling characterization of various samples without the need for vision system processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional force sensing systems are used, then force measurement is possible, but direct simultaneous measurement of position and force is not possible, requiring image processing

Engineering Contradiction:

Improveforce measurement precisionVSAvoidmeasurement system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent combines force sensing capabilities with position measurement capabilities into a single integrated sensor system. The capacitive force sensor measures both force applied to the sample and position of the manipulator simultaneously, eliminating the need for separate vision systems and image processing, thus resolving the contradiction between measurement precision and device complexity

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The sensor system is designed to perform multiple functions: force measurement, position measurement, and deformation measurement all through the same integrated system. This multi-functional approach allows simultaneous direct measurement of multiple parameters without requiring separate specialized systems

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If conventional systems with fixed sensing direction are used, then specific sample types can be characterized, but extensive sample preparation is required for diverse sample types

Engineering Contradiction:

Improvemeasurement reliabilityVSAvoidsample type adaptability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent implements a dynamically adjustable sensing system where the sensing direction of the force sensor can be changed during measurements. This allows the system to adapt to different sample orientations and types without requiring extensive sample preparation, maintaining measurement reliability while increasing versatility

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system is designed with universal adaptability to handle diverse sample types including biological samples, materials, and microstructures. The combination of adjustable sensing direction and integrated measurement capabilities makes the system universally applicable across different research domains without requiring sample-specific customization

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Measurement precision

If high-resolution force sensing is implemented, then sub-millinewton measurement is possible, but sensor size increases which limits space between sample and microscope lens

Engineering Contradiction:

Improveforce sensing resolutionVSAvoidsensor size

Core Design Contradiction:

Measurement precisionVSVolume of moving object

Solution Approach 1:

The patent replaces traditional mechanical force sensing mechanisms with capacitive sensing technology. This substitution enables high-resolution sub-millinewton force measurement while maintaining a compact sensor form factor that fits within the limited space between the sample and microscope lens

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 accurate and versatile mechanical characterization of small-sized samples across different orientations and applications, providing direct force and deformation measurements, and allowing for a range of mechanical property assessments, including Young's modulus, adhesion, and friction forces, with improved precision and reduced sample preparation.

Implementation Method 1

The force sensor can be a capacitive force sensing MEMS probe, a capacitive cantilever-type force sensor

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

Integrated encoders in the manipulators simultaneously measure the position and deformation of the sample

Methodology Applied

Scientific EffectEncoder measurement:

Data Source

PatentEP2480925B1System for mechanical characterization of materials and biological samples in the sub-millinewton force range

Publication Date: 2018.11.28 FEMTOTOOLS

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Figure 3a~3f

AI summary

The mechanical characterization system consists of three main parts: A sub-millinewton resolution capacitive force sensor; at least one micromanipulator with position measurement capabilities and a microscope The sensitive axis of the force sensor is via adaptor pieces adjustably connected to the micromanipulator at any angle relative to the sample holder.