3D Printed Hydroxyapatite Scaffolds Room-Temperature Printing
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Solution Overview
Problem
Current 3D printing methods for bone scaffolds are limited by low resolution, low ceramic content in printing inks, and high-temperature printing, which results in scaffolds with poor mechanical strength and bio-related disadvantages, such as low elasticity and viability issues for cell printing.
Innovation Solution
The development of 3D-printed scaffolds with high hydroxyapatite content using non-aqueous Calcium Phosphate Cement (CPC) slurries and a sodium phosphate dibasic bath for room-temperature printing, allowing for precise control of porosity and mechanical strength, and the use of a motor-driven syringe extruder to create biocompatible, osteoconductive, and biodegradable structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If current 3D printing methods are used to fabricate bone scaffolds, then the printing process can be completed, but the resolution is low and filament resolutions cannot be less than 200 μm
Solution Approach 1:
The patent changes the physical and chemical parameters of the printing material by using calcium phosphate cement slurries with optimized viscosity and particle size distribution, enabling high-resolution printing at room temperature without compromising the printing process feasibility
Solution Approach 2:
The patent uses composite calcium phosphate cement materials combining different calcium phosphate phases (tetracalcium phosphate, dicalcium phosphate anhydrous) with controlled particle sizes, achieving both high resolution and manufacturability
2Strength
If current 3D printing methods use printing inks with high ceramic material content (>75% of total), then the scaffolds have high mechanical strength, but the printing process becomes difficult due to material viscosity and nozzle clogging
Solution Approach 1:
The patent optimizes the slurry parameters including viscosity, particle size distribution, and liquid-to-powder ratio, enabling high ceramic content (75-85 wt%) materials to be printed without clogging while achieving compressive strength >5 MPa
Solution Approach 2:
The patent uses a carefully formulated slurry medium containing calcium phosphate cement powders dispersed in liquid phase with specific rheological properties, acting as an intermediary that enables high ceramic content to be processed through standard printing nozzles
3Reliability
If high-temperature printing is used to fabricate scaffolds, then the ceramic materials can be sintered properly, but cell viability is compromised and bio-related advantages are lost
Solution Approach 1:
The patent changes the processing temperature parameter from high-temperature sintering to room-temperature printing, followed by in situ hydroxyapatite formation in physiological conditions, preserving cell viability while achieving adequate mechanical strength through compositional optimization
Solution Approach 2:
The patent uses composite calcium phosphate cement materials that can set and gain strength at room temperature through chemical reactions, eliminating the need for high-temperature processing that would kill cells
4Adaptability or versatility
If conventional casting or mold methods are used to fabricate scaffolds, then the manufacturing process is simple, but patient-specific geometry cannot be achieved
Solution Approach 1:
The patent enables local customization of scaffold geometry, porosity, and mechanical properties throughout the structure to match patient-specific anatomical requirements, achieved through digital modeling and precise material deposition control
Solution Approach 2:
The patent replaces conventional mechanical casting and molding systems with additive manufacturing technology, enabling complex patient-specific geometries to be built layer-by-layer from digital designs without requiring complex molds or tooling
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
The method enables the production of biocompatible scaffolds with controlled porosity and mechanical strength, suitable for bone grafting and regeneration, with improved cell growth and predictability, and the ability to print at room temperature, avoiding nozzle clogging and cell damage.
Implementation Method 1
3D printing of calcium phosphate cement (CPC) slurries in an aqueous bath containing sodium phosphate dibasic (Na2HPO4) which helps the CPC slurry to harden and form hydroxyapatite (HA) in situ
Implementation Method 2
The solvent evaporates to produce, under influence of a hardening accelerator, a biocompatible hydroxyapatite/polymer composite scaffold
Data Source
AI summary
A three-dimensional, biocompatible scaffold precursor composition for room-temperature printing a bio-compatible polymer/hydroxyapatite composite scaffold includes a room-temperature slurry, comprising a mixture of a sold phase that includes a mixture of tetracalcium phosphate (TTCP; Ca4(PO4)2O) and dicalcium phosphate anhydrous (DCPA; CaHPO4), and a liquid phase that includes a polymer in a solvent. The solvent may be Ethanol (EtOH) or Tetrahydrofuran (THF), and the polymer may be polyvinyl butyral (PVB), polycaprolactone (PCL), or poly lactic-co-glycolic acid (PLGA). The slurry is printed at room temperature in aqueous phosphate (NaH2PO4) bath, which works as hardening accelerator, forming the polymer/hydroxyapatite composite scaffold.