Microwave Heating Microfluidic Device for Rapid Thermal Cycling

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Solution Overview

Problem

Current microfluidic devices face inefficiencies in heating chemical reactor volumes within their channels, as they also heat the entire substrate, leading to prolonged cooling times during cyclical reactions, which hampers processes like PCR and diagnostics.

Innovation Solution

A micro-electro-mechanical system (MEMS) with a micro-channel flow channel, a carrier fluid, and a microwave source that directs microwaves onto the sample without heating the substrate or carrier fluid, utilizing microwave energy absorption for rapid and efficient thermal energy deposition and removal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If conventional heating methods are used to heat chemical reactor volumes in microfluidic channels, then the required thermal energy can be supplied, but the entire substrate is also heated leading to prolonged cooling times

Engineering Contradiction:

Improveheating speedVSAvoidcooling time

Core Design Contradiction:

TemperatureVSLoss of time

Solution Approach 1:

The patent applies local quality by making the microwave heating highly localized to the sample volume within the microchannel. The microwave source is positioned and configured to deliver energy only to the aqueous sample, not the surrounding substrate or carrier fluid. This selective localized heating allows rapid temperature increase in the reaction zone without heating the entire device, thereby solving the contradiction between fast heating and long cooling times.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent segments the system into distinct thermal zones: the sample volume that is rapidly heated by microwaves, the carrier fluid that remains relatively cool, and the substrate that is minimally affected. This segmentation allows the heated sample to be quickly cooled by the cooler carrier fluid and surrounding structures, dramatically reducing cooling time while maintaining effective heating when needed.

Inventive Principle:

Principle #1Segmentation

2Use of energy by moving object

If conventional heating methods are used, then thermal energy can be supplied to drive endothermic reactions, but heat diffusion distance and thermal mass increase with larger channel dimensions

Engineering Contradiction:

Improveheating efficiencyVSAvoidreaction speed

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

The patent replaces conventional thermal conduction-based heating (which relies on heat diffusion through the substrate and fluid) with microwave dielectric heating. This substitution enables direct volumetric heating of the sample without relying on heat diffusion from external sources, dramatically improving heating efficiency and enabling rapid thermal cycling for fast reactions.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Speed

If microwave heating is applied to aqueous samples, then rapid heating can be achieved, but the substrate and carrier fluid may also be heated reducing efficiency

Engineering Contradiction:

Improveheating speedVSAvoidenergy waste

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

The patent makes different parts of the system have different microwave absorption properties: the aqueous sample is designed to strongly absorb microwaves (high dielectric loss), while the substrate and carrier fluid are selected to be microwave-transparent or have minimal absorption. This local quality differentiation ensures that microwave energy is converted to heat only where needed (in the sample), achieving rapid heating without wasting energy heating other components.

Inventive Principle:

Principle #3Local quality

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

This method enables near-instantaneous thermal energy deposition and removal, significantly reducing processing times by an order of magnitude, making real-time processes like PCR feasible, and enhancing applications in biowarfare detection, infectious disease monitoring, and chemical synthesis.

Implementation Method 1

utilizing microwave energy absorption for rapid and efficient thermal energy deposition

Methodology Applied

Scientific EffectMicrowave absorption: Absorption (EM radiation)

Implementation Method 2

Microwave heating of aqueous solutions exhibits excellent energy deposition due to the polarization of the water molecules

Methodology Applied

Scientific EffectDielectric heating: Dielectric Heating

Data Source

PatentUS10123380B2Instantaneous in-line heating of samples on a monolithic microwave integrated circuit microfluidic device

Publication Date: 2018.11.06 LAWRENCE LIVERMORE NAT SECURITY LLC

AI summary

A micro-electro-mechanical system for heating a sample including a substrate, a micro-channel flow channel in the substrate, a carrier fluid within the micro-channel flow channel for moving the sample in the micro-channel flow channel, and a microwave source that directs microwaves onto the sample in the micro-channel flow channel for heating the sample. The carrier fluid and the substrate are made of materials that are not appreciably heated by the microwaves. The microwave source includes conductive traces or strips and a microwave power source connected to the conductive traces or strips.