Opaque Substrate Microfluidic Chip with Transparent Window
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Solution Overview
Problem
The challenge of performing transmission optical measurements in a vessel with an opaque substrate is that the light is blocked by the substrate, making it difficult to obtain accurate measurements, especially for applications like flow cytometry where forward scatter measurements are crucial.
Innovation Solution
A method is developed to produce a microfluidic chip with an opaque substrate, where a continuous transparent layer is deposited on the substrate using vapour deposition, and an aperture is etched through the substrate to allow light to pass through, enabling transmission optical measurements without distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a transparent layer is deposited on the opaque substrate to enable optical measurements, then transmission optical measurements can be performed, but the transparent layer may become distorted during etching
Solution Approach 1:
A resist layer is introduced as an intermediary protective layer between the etchant and the transparent layer. The resist layer is applied to the first surface of the substrate, covering the transparent layer, and serves as a barrier during the etching process to prevent the etchant from contacting and distorting the transparent layer. This mediator approach allows the etching to proceed while preserving the optical integrity of the transparent layer.
2Measurement precision
If the transparent layer is made thinner to improve optical smoothness, then optical quality improves, but the layer becomes more vulnerable to damage during handling and processing
Solution Approach 1:
The resist layer is applied in advance before the etching process to cushion and protect the thin transparent layer from mechanical and chemical damage. This prior protective measure allows the transparent layer to be made thinner for improved optical smoothness while the resist layer provides the necessary structural support and damage prevention during subsequent handling and processing steps.
3Ease of operation
If an aperture is etched through the substrate to allow light transmission, then transmission measurements are enabled, but the etching process may distort the transparent layer
Solution Approach 1:
The resist layer serves as a protective intermediary that is applied to the first surface of the substrate before etching. It covers and protects the transparent layer during the aperture etching process, preventing the etchant from reaching and distorting the transparent layer. This allows the aperture to be successfully etched through the substrate for light transmission while maintaining the optical smoothness of the transparent layer.
4Manufacturing precision
If vapour deposition is used to deposit the transparent layer, then conformal contact and optical smoothness are achieved, but the layer may be reactive to subsequent etching processes
Solution Approach 1:
The resist layer is applied as a protective intermediary over the vapour-deposited transparent layer before the etching process. This mediator prevents the etchant from directly contacting the transparent layer, eliminating the reactivity issue while preserving the conformal contact quality and optical smoothness achieved through vapour deposition.
Solution Approach 2:
The resist layer is applied in advance before etching to pre-protect the transparent layer from chemical attack. This preliminary protective action prevents the reactivity problem between the vapour-deposited layer and the etchant, allowing the transparent layer to maintain its conformal contact quality and optical properties throughout the subsequent etching process.
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 allows for accurate transmission optical measurements, such as forward scattering, by ensuring the continuous transparent layer remains optically smooth and resistant to etching, enabling thinner layers and improved optical properties while maintaining structural integrity.
Implementation Method 1
providing a continuous transparent layer across said first surface by vapour deposition so as to provide conformal contact between the continuous transparent layer and the first surface of the substrate
Implementation Method 2
Light incident on particles in the flow channel is able to pass through both the continuous transparent layer and the aperture without distortion
Data Source
AI summary
A method of producing a microfluidic chip for use in flow cytometry, the method comprising the steps of providing an opaque substrate, a first surface of which is optically smooth for visible light providing a continuous transparent layer across said first surface by vapour deposition so as to provide conformal contact between the continuous transparent layer and the first surface of the substrate providing a flow channel bounded on a first side by the continuous transparent layer and etching an aperture in a second surface of the substrate extending to the first surface of the substrate so as to provide an optical path between said second surface and the flow channel wherein the continuous transparent layer is less reactive to the etching than the substrate.