Microfluidic Device Stress Dispersion and Liquid Tightness
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Solution Overview
Problem
Microfluidic chips are prone to damage and liquid leakage when high-pressure fluid samples are fed due to insufficient holding force and excessive stress, which existing chip holders and connectors fail to adequately address.
Innovation Solution
A microfluidic device design featuring a chip holder with a cover and base that maintain surface flatness and planarity within specific limits, along with a connector system that includes a recessed portion and a ferrule with controlled tensile strength, to reduce stress on the chip and enhance liquid tightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a sample is fed at high pressure to improve productivity, then the flow rate increases, but liquid leakage occurs at the connection portion due to insufficient holding force
Solution Approach 1:
The connector is designed with a pressing portion that pre-compresses the O-ring seal before high-pressure fluid flow begins. This preliminary sealing action ensures the connection is already sealed and ready to withstand the upcoming high-pressure sample injection, preventing liquid leakage while maintaining high flow rates
Solution Approach 2:
An O-ring seal is introduced as an intermediary element between the connector and the microfluidic chip connection portion. This O-ring acts as a mediator that enhances the sealing capability, allowing the system to maintain liquid tightness under high-pressure conditions without requiring excessive holding force from the chip holder alone
2Reliability
If the pressing force of the ferrule is increased to avoid liquid leakage, then liquid tightness improves, but the microfluidic chip may be damaged due to excessive stress
Solution Approach 1:
The O-ring seal serves as an intermediary that assumes the sealing function, allowing the ferrule to apply minimal pressing force. This mediator approach prevents the ferrule from directly transmitting excessive stress to the microfluidic chip while still achieving reliable liquid tightness at the connection portion
Solution Approach 2:
The design changes the sealing mechanism from direct mechanical compression (ferrule pressing directly on chip) to elastomeric sealing (O-ring compression). This parameter change in the sealing approach allows effective sealing at lower pressing forces, protecting the chip from damage while maintaining liquid tightness
3Reliability
If the holding force of the chip holder is increased to prevent liquid leakage, then liquid tightness improves, but the microfluidic chip may be deformed due to excessive stress
Solution Approach 1:
The O-ring seal acts as an intermediary sealing element that localizes the compression force at the connection interface rather than distributing it across the entire chip surface. This prevents excessive stress from deforming the chip while maintaining effective sealing at the critical connection portion
Solution Approach 2:
The sealing function is localized to the connection portion where the O-ring is positioned, rather than requiring uniform compression across the entire chip. This local quality approach allows strong sealing at the connection interface without applying excessive holding force that would deform the chip structure
Data Source
AI summary
A microfluidic device includes: a microfluidic chip with a flow path formed inside; a cover and a base, each in contact with a surface of the microfluidic chip; a chip holder including a fixture for securing the microfluidic chip to the cover and the base; and a connector with one end in contact with a surface of the microfluidic chip and the other end serving as a fluid supply or discharge port. The flatness of the surfaces of the microfluidic chip is 50 μm or less, and the planarity of the surfaces of the cover and base is 50 μm or less. By this structure, the microfluidic chip is hardly deformed, and damage to the microfluidic chip is suppressed. In addition, liquid tightness at a connection portion with the flow path of the microfluidic chip is high, and liquid leakage hardly occurs.