Microfluidic Switch Using Vapor Bubbles for Flow Control
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Solution Overview
Problem
Existing microfluidic systems face challenges in dynamically redirecting fluid and particle flow due to continuous dilution of sample fluid and slow response times, requiring flexible electrometric channels and opaque targets, which are not durable and efficient.
Innovation Solution
A microfluidic switch is created using vapor bubbles within a pathway, controlled by optical switches or spatial light modulators, where cavitation bubbles are created and re-condensed to block or allow fluid flow, maintaining a constant flow rate by alternating bubble locations, using high-power density laser energy in far ultraviolet or infrared spectra.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If vapor bubbles are created by heating effect of laser light absorbed by gold target on channel wall, then fluid flow can be controlled, but response time is slow (several milliseconds) and channel walls require opaque targets reducing durability
Solution Approach 1:
The patent replaces the thermal heating mechanism (mechanical/thermal system) with an optical absorption mechanism. Instead of using laser light to heat a gold target which then transfers heat to the fluid, the invention uses laser light directly absorbed by the fluid to create vapor bubbles. This substitution enables faster response times (1-100 μs vs several milliseconds) and eliminates the need for opaque targets on channel walls, allowing use of durable transparent materials like glass or quartz.
Solution Approach 2:
The patent changes the physical parameters of the system by selecting laser wavelengths in the far ultraviolet or far infrared portions of the spectrum where the fluid has high absorption coefficients (several orders of magnitude greater than in visible spectrum). This parameter change enables direct fluid absorption of laser energy, achieving rapid vapor bubble formation without requiring opaque targets, thus resolving both the speed and durability contradictions.
2Productivity
If particles are selectively deflected to enter one or the other channel, then sorting can be achieved, but fluid flow is present in both paths at all times causing continuous dilution of sample fluid
Solution Approach 1:
The patent employs periodic action by dynamically creating and collapsing vapor bubbles in one channel while simultaneously blocking the other channel. This periodic switching of flow paths ensures that at any given moment, particles are directed to a single channel while the other channel is blocked, preventing dilution. The rapid bubble formation (1-100 μs) enables high-speed sorting while maintaining sample concentration.
Solution Approach 2:
The system uses dynamic control of vapor bubble formation and collapse to actively manage fluid flow paths in real-time. By rapidly switching which channel is blocked through controlled vaporization and condensation cycles, the system achieves both high-speed particle sorting and prevention of sample dilution, as the flow paths are dynamically adjusted rather than statically configured.
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 solution enables precise, high-speed redirection of fluid and particles, maintaining a constant flow rate and preventing dilution, using rigid materials and eliminating the need for flexible channels or opaque targets, thus improving the efficiency and durability of microfluidic systems.
Implementation Method 1
vapor bubbles are created in a medium by non-linear means, including but not limited to, multiple photon absorption due to the high power density (greater than 1 MW/cm squared) of the focused light
Implementation Method 2
A fluid is flowed through a microfluidic pathway and a cavitation bubble is created using an optical element within the pathway to block fluid flow within the fluidic pathway
Implementation Method 3
the light of the laser is in the far ultraviolet or far infrared portions of the spectrum, where significant absorption of the light will occur within the dimensions of the channel cross section, by virtue of the light absorption coefficient of the fluid being several orders of magnitude greater at these frequencies than in the visible spectrum
Implementation Method 4
Small 10-100 μm vapor bubbles can be created within 1-100 μS of turning on a laser and they will also re-condense into liquid in approximately the same time frame when the laser is turned off
Data Source
AI summary
Fluid is flowed into an inlet channel of a microfluidic pathway at a flow rate, the microfluidic pathway including a first and second outlet channels fluidically connected to the inlet channel. A first cavitation bubble is created within the first outlet channel to block fluid flow out of the first outlet channel. A second cavitation bubble is created within the second outlet channel to block fluid flow out of the second outlet channel. Creation of the second cavitation bubble is initiated during or after the first cavitation bubble dissolves such that the flow rate is maintained.