Parylene Microcapillary Fabrication via Sacrificial PEC Fiber
Solution Overview
Problem
Existing methods are inefficient in manufacturing small diameter capillaries of long lengths, as standard techniques are limited to capillaries of up to 80 microns in diameter and a few millimeters in length due to time-consuming chemical etching and difficulties in maintaining uniformity and length.
Innovation Solution
A method involving the drawing of a sacrificial polyethylene carbonate (PEC) fiber from a chloroform solution, coating with parylene, and heating to expel the PEC, creating a hollow capillary with a self-expelling mechanism that allows for centimeter to meter-long capillaries with uniform diameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chemical etching is used to manufacture small diameter capillaries, then capillary diameter can be reduced, but manufacturing time increases quadratically with fiber length
Solution Approach 1:
The patent extracts the core problem of time-consuming etching by replacing the etching process entirely with a direct drawing process. Instead of creating capillaries by removing material through chemical etching, the invention draws capillaries directly from molten polymer using capillary action, eliminating the quadratic time penalty associated with etching longer fibers.
Solution Approach 2:
The patent replaces the chemical etching process with a mechanical drawing process. By using capillary action and controlled pulling forces, the system mechanically forms capillaries directly from molten polymer, substituting a time-efficient mechanical process for the slow chemical etching process.
2Manufacturing precision
If standard commercial techniques are used, then capillaries can be manufactured with diameters down to 80 microns, but lengths are limited to a few millimeters
Solution Approach 1:
The patent changes the fundamental parameters of the manufacturing process by using direct drawing from molten polymer rather than etching solid material. This parameter change enables continuous production of long capillaries with uniform diameter control, achieving lengths of meters while maintaining precise diameter control down to micrometer scales.
Solution Approach 2:
The patent performs preliminary heating of the polymer to a molten state before drawing, creating a fluid medium that can be easily shaped and pulled into long capillaries. This preliminary action of melting the polymer enables the subsequent drawing process to produce continuous long-length capillaries without the length limitations of etching methods.
3Length of moving object
If polymer bridges are drawn between multiple droplets, then longer fibers can be achieved, but the capillaries develop catenary-shaped sections with non-uniform diameter
Solution Approach 1:
The patent creates a uniform drawing environment by maintaining consistent temperature and pulling force throughout the entire drawing process. By ensuring equipotential conditions in terms of thermal and mechanical fields, the system produces capillaries with uniform diameter along their entire length, avoiding the catenary distortions that occur when polymer bridges sag under their own weight between droplets.
Solution Approach 2:
The patent uses a single continuous drawing process that copies the uniform diameter profile along the entire length of the capillary. By maintaining constant drawing parameters (temperature, pulling speed, capillary radius), the system reproduces the same cross-sectional geometry throughout the length of the capillary, ensuring diameter uniformity without the variations introduced by multi-droplet assembly.
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 significantly extends the length of small diameter capillaries beyond previous limitations, achieving lengths of over 30 cm with uniformity and reduced production time, using PEC fibers coated with parylene, and allows for the production of capillaries with diameters as small as 3 μm.
Implementation Method 1
allowing the chloroform to evaporate to solidify the drawn PEC fiber
Implementation Method 2
depositing parylene by chemical vapor deposition on the PEC fiber to coat the PEC fiber
Implementation Method 3
heating the coated PEC fiber to a temperature between 180° C. and a melting point of the parylene, thereby melting the PEC
Implementation Method 4
partially decomposing the PEC into gaseous carbon dioxide
Implementation Method 5
partially decomposing the PEC into gaseous carbon dioxide, such that the gaseous carbon dioxide pushes the molten PEC out
Data Source
AI summary
A parylene microcapillary is manufactured by drawing a polyethylene carbonate (PEC) fiber from a 0° C. solution of 12-25% PEC in chloroform to create a PEC fiber that has a constant diameter over several centimeters. Parylene is deposited in a chamber over the PEC fiber, and then the coated PEC fiber is heated above 180° C. This heating melts and decomposes the PEC fiber such that it self-expels from the coating, leaving a microcapillary. The self-expulsion allows for meters-long lengths of microcapillaries. Alternatively, a serpentine fiber channel of PEC is created by deposition, photolithography, and etching within a sandwich of parylene. It is heated above 180° C. to expel the PEC leaving a hollow channel within a mass of parylene. The resulting microcapillaries may have residues of cyclic ethylene carbonate remaining from the decomposed PEC.