3D-Printed PDMS Organ-on-a-Chip With Thermal Laser Curing
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Solution Overview
Problem
Existing 3D printing methods for polydimethylsiloxane (PDMS) parts are limited by feature resolution and require UV curing, which introduces UV absorbers or activators, leading to inferior parts and unknown toxicity, while traditional thermal curing is hindered by layer-to-layer registration issues.
Innovation Solution
A method for thermally curing PDMS layers using a 9.3 micrometer wavelength laser to achieve precise layer-to-layer registration and feature resolution below 200 micrometers without UV initiators, employing a 10:1 PDMS to thermal curing agent ratio and spin coating for rapid layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UV curing is used to manufacture PDMS parts, then the parts can be cured, but the parts become yellowish and require UV absorbers or activators which are considered inferior and have unknown toxicity
Solution Approach 1:
The patent removes UV absorbers or activators from the PDMS formulation entirely, extracting the harmful component while maintaining curing capability through thermal curing alone. This eliminates the yellowish coloration and potential toxicity associated with UV additives.
Solution Approach 2:
The patent changes the curing mechanism from UV-based to thermal-based by controlling temperature parameters. By using a heated stage at controlled temperatures (e.g., 60-100°C), the PDMS cures through thermal activation rather than UV absorption, fundamentally changing the curing parameter from optical to thermal.
2Object-affected harmful factors
If traditional thermal curing is used without UV absorbers, then the parts remain clear and non-toxic, but layer-to-layer registration accuracy deteriorates
Solution Approach 1:
The patent applies a release coating to the build plate before depositing the first PDMS layer. This preliminary action prevents adhesion between layers, enabling precise layer-to-layer registration by allowing easy removal and repositioning of subsequent layers without compromising alignment accuracy.
Solution Approach 2:
The patent replaces mechanical alignment methods with optical alignment using a camera system. The camera captures images of fiducial markers on each layer, and image processing algorithms automatically calculate and correct registration transformations, substituting mechanical precision requirements with optical measurement and computational correction.
3Productivity
If vat polymerization 3D printing is used, then PDMS layers can be formed, but the curing depth is limited to around 200 micrometers which reduces accuracy
Solution Approach 1:
The patent segments the PDMS into very thin layers (e.g., 10-50 micrometers) rather than attempting to cure thick layers. This segmentation allows each thin layer to be uniformly and accurately cured, achieving high precision features below 200 micrometers while maintaining productive layer formation rates.
Solution Approach 2:
The patent uses periodic heating cycles where the build plate is heated to cure the current layer, then cooled before the next layer is deposited. This periodic thermal action ensures complete curing of each thin layer while allowing precise control over the curing process, achieving both productivity and high accuracy.
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
Enables the production of PDMS parts with features as thin as 1 micrometer, overcoming layer registration issues and eliminating the need for UV additives, resulting in high-resolution microfluidic devices with improved accuracy and repeatability.
Implementation Method 1
curing at least a portion of the heat curable current layer by selectively applying an incident electromagnetic radiation energy to heat at least a portion of the heat curable current layer
Implementation Method 2
thermally curing layers of PDMS using a 9.3 micrometer wavelength laser
Implementation Method 3
spin coating for rapid layer formation
Implementation Method 4
less than 50% of the incident electromagnetic radiation energy is transmittable through 1 micron of the heat curable mixture
Data Source
AI summary
A process to additively manufacture a three dimensional part includes the steps of sequentially forming layers of a thermally curable mixture of polydimethylsiloxane (PDMS) and a curing agent, selectively thermally curing the individual layer by heating the layer with a focused electromagnetic radiation where less than 60% of the electromagnetic radiation passes through 1 micron of the heat curable mixture. The three dimensional part is then cleaned of any uncured heat curable mixture.