Sessile Drop Shape Determination via Capacitance Measurement

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Solution Overview

Problem

Existing methods for determining the shape of sessile drops, particularly those with small diameters or obstructed optical paths, are limited in accuracy and effectiveness.

Innovation Solution

Measuring first and second shape parameters, such as drop height and radius of curvature, optically and vertically, without visual inspection, to calculate third shape parameters like wetting contact angle, using geometric models like spherical or oblate spheroid models, even when optical paths are obstructed.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If lateral measurement and visual inspection methods are used to determine drop shape, then the measurement process is simple and direct, but the method cannot be used for small drops (diameter < 1 μm) or when optical paths are obstructed

Engineering Contradiction:

Improvemeasurement simplicityVSAvoidapplicability to small drops and obstructed scenarios

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The patent replaces traditional optical/mechanical lateral measurement systems with an electrical measurement system. Specifically, it measures capacitance between the drop and substrate, and between the drop and ground, to determine drop shape parameters. This electrical field-based approach works for sub-micron drops and obstructed optical paths where optical methods fail.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces capacitance measurements as an intermediary parameter to indirectly determine drop shape. Instead of directly measuring geometric parameters optically, it measures electrical capacitance values (C1 between drop and substrate, C2 between drop and ground) and uses these as intermediaries to calculate contact angle and other shape parameters through established relationships.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If optical measurement systems are used to measure drop profile, then direct visual inspection is possible, but the optical path may be obstructed and small drops cannot be measured

Engineering Contradiction:

Improvedirect optical measurement capabilityVSAvoidmeasurement capability for small and obstructed drops

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent substitutes optical measurement systems with electrical field-based capacitance measurement systems. The capacitance measurement apparatus uses electrical fields that can penetrate obstructions and detect sub-micron drops, replacing the optical path-based detection that fails in these conditions.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the measurement parameter from optical geometric parameters (requiring visible light paths) to electrical parameters (capacitance values). This parameter transformation enables measurement of drops that are invisible or inaccessible to optical systems, including sub-micron drops and drops in obstructed environments.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If contact angle is measured directly by visual inspection of drop profile, then the measurement is straightforward, but it cannot determine shape parameters for drops where optical paths are blocked

Engineering Contradiction:

Improvedirect contact angle measurementVSAvoidmeasurement reliability in obstructed and small drop scenarios

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent uses capacitance measurements as intermediary parameters to indirectly determine contact angle. Instead of directly visualizing the contact angle, it measures capacitance values (C1, C2) and calculates contact angle from these electrical parameters using established relationships between capacitance and contact angle, enabling reliable measurement in previously inaccessible scenarios.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the visual inspection mechanism with an electrical field-based measurement mechanism. The capacitance measurement system uses electrical fields to probe the drop-substrate system, replacing the optical visualization approach and enabling contact angle determination for sub-micron and obstructed drops with high reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS9791265B2Methods of determining the shape of a sessile drop

Publication Date: 2017.10.17 JUNIVERSITI OF NORT KAROLINA EHT SHARLOTT

AI summary

In one aspect, methods of determining the shape of a sessile drop are described herein. In some embodiments, a method described herein comprises measuring a first shape parameter of a sessile drop to obtain a first shape parameter value, measuring a second shape parameter of the drop to obtain a second shape parameter value, and using the first and second shape parameter values to calculate a third shape parameter value of a third shape parameter of the drop.