Strain-Driven Microfluidic Pumping via Negative Volumetric Strain

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Solution Overview

Problem

Existing microfluidic wearable devices are limited by finger-triggered mechanisms and require external power sources, restricting their portability and usability in wearable applications.

Innovation Solution

A microfluidic device with a negative volumetric strain under tensile strain, capable of pumping fluids through a microfluidic channel using skin deformation during human movements, eliminating the need for external power sources.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If finger-triggered mechanisms are used for microfluidic pumping, then the device can be operated manually, but it requires intentional user action and reduces ease of operation for continuous pumping

Engineering Contradiction:

Improveease of operationVSAvoidautomation

Core Design Contradiction:

Ease of operationVSExtent of automation

Solution Approach 1:

The microfluidic device actuates automatically in response to skin strain from any human movement without requiring intentional user action. The strain-driven mechanism self-activates when the wearable device experiences deformation during natural body movements, enabling autonomous pumping operation

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The device utilizes changes in physical parameters (skin strain, deformation) to trigger pumping action. By converting mechanical strain from any movement into fluid pumping through the microfluidic channel, the system responds to varying strain parameters automatically

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If standard elastomeric strain sensors with positive Poisson's ratio are used, then the material exhibits typical elastic behavior, but it causes volumetric expansion under tensile strain which limits pumping efficiency

Engineering Contradiction:

Improvematerial stabilityVSAvoidpumping efficiency

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The device employs mechanical metamaterials with customized Poisson's ratios that differ from standard elastomeric materials. These engineered materials exhibit negative volumetric strain under tensile strain, enabling enhanced pumping efficiency while maintaining structural stability

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention changes the fundamental material parameter (Poisson's ratio) from the typical positive range (0-0.5) to customized values that produce negative volumetric strain. This parameter change transforms the material's response to tensile strain, converting volumetric expansion into volumetric contraction for improved pumping

Inventive Principle:

Principle #35Parameter changes

3Reliability

If external power sources are used for microfluidic pumping, then reliable fluid transport is achieved, but portability and usability in wearable applications are restricted

Engineering Contradiction:

ImprovereliabilityVSAvoidportability

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The device replaces external power sources with a strain-driven mechanical actuation system. Human body movement generates the mechanical strain needed to drive fluid pumping through the microfluidic channel, eliminating batteries and power electronics

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The pumping system uses the wearer's own body movement as the power source. The strain from any human motion automatically actuates the microfluidic pump, making the device self-powered and eliminating the need for external power supplies

Inventive Principle:

Principle #25Self-service

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 device achieves power-free, continuous fluid pumping with precise and consistent flow control, enhancing portability and usability in wearable applications.

Implementation Method 1

In-plane tensile strain causes volumetric expansion in microfluidic channels

Methodology Applied

Scientific EffectVolumetric expansion: Thermal Expansion

Implementation Method 2

Mechanical metamaterials when subjected to tensile strain, can exhibit lateral extension (Poisson's ratio 0.5) causing volume reduction rather than dilatation

Methodology Applied

Scientific EffectPoisson's ratio effect: Poisson's Effect

Data Source

PatentUS20250025875A1Fluid Pumping and Reversible Flow in Strain Driven Microfluidic Applications

Publication Date: 2025.01.23 SANTA CLARA UNIVERSITY

AI summary

A microfluidic device is provided that has a negative volumetric strain under a tensile strain. The microfluidic device is capable of pumping fluids stored inside a reservoir towards an outlet through a microfluidic channel. The pumping mechanism is actuated by repeated (e.g., once or multiple times) application of in-plane tensile strain. The in-plane strain can be due to the skin deformation during human movements for a skin-mounted wearable device and related applications.