Porous Ceramic Articles via Polymer Dissolution
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Solution Overview
Problem
Conventional methods for forming porous ceramic shaped articles with macropores for biomedical applications face challenges in achieving controlled pore size distribution and interconnectivity, with existing methods like sugar-based sacrifying phases leading to unpredictable results and difficulties in shaping.
Innovation Solution
A method involving a precursor powder mixture of polymer particles and ceramic self-setting cementitious powder, where the polymer particles are dissolved in an immersing liquid to create pores, allowing for controlled porosity and macroporosity, with polyethylene glycol used to achieve specific particle sizes and dissolution rates for uniform pore formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sugar-based sacrifying phase is used to create macropores, then pore formation is achieved, but pore size distribution and interconnectivity become unpredictable
Solution Approach 1:
The patent uses polyethylene glycol (PEG) particles as a sacrificial phase that dissolves completely during the setting process, leaving behind controlled macropores. The PEG particles are inexpensive and temporarily serve their purpose of creating pore spaces, then are removed through dissolution in water, achieving reliable and consistent pore formation without the unpredictability of sugar-based phases.
Solution Approach 2:
The patent controls pore size distribution by carefully selecting and controlling the particle size distribution of the PEG particles. By changing the physical parameters of the sacrificial phase (particle size, size distribution), the method achieves predictable and controllable macropore characteristics in the final cement structure.
2Quantity of substance
If sugar is used as sacrifying phase, then macropores are created, but the sugar dissolves before cement setting starts, affecting setting mechanism
Solution Approach 1:
The patent employs PEG particles as a temporary sacrificial component that maintains structural integrity during mixing and setting, then dissolves afterward. The PEG particles are hydrophilic but do not interfere with the cement setting chemistry, allowing the cement to set properly first, then the PEG dissolves in body fluids or water to create the desired macropores.
Solution Approach 2:
The PEG particles are pre-incorporated into the cement mixture in a controlled manner before setting occurs. The particles are distributed uniformly throughout the paste, ensuring that macropores will form in predetermined locations and quantities after the cement has set and the PEG subsequently dissolves.
3Quantity of substance
If mechanical foaming is used to create pores, then porosity is increased, but pore distribution and interconnectivity are difficult to control
Solution Approach 1:
Instead of using mechanical foaming which creates unpredictable air bubble distributions, the patent uses solid PEG particles as a sacrificial phase. These particles can be precisely controlled in terms of size, shape, and distribution before being incorporated into the cement. After setting, the PEG particles dissolve to leave behind macropores with controlled distribution and interconnectivity.
Solution Approach 2:
The patent achieves controlled pore distribution by controlling the particle size distribution, concentration, and spatial arrangement of the PEG particles in the precursor mixture. By adjusting these parameters, the method produces cements with predictable macropore characteristics, including size, distribution, and interconnectivity.
4Manufacturing precision
If polyethylene glycol particles are used as sacrifying phase, then controlled macroporosity is achieved, but dissolution time must be carefully managed
Solution Approach 1:
The patent controls the dissolution rate of PEG particles by selecting appropriate molecular weights and particle sizes. Lower molecular weight PEG dissolves faster, while higher molecular weight and larger particle sizes result in slower dissolution. This allows optimization of the dissolution time to match the desired clinical timeline for bone ingrowth while maintaining controlled macropore formation.
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 produces ceramic shaped articles with controlled porosity and macroporosity, enhancing bone ingrowth and cell colonization, while avoiding the drawbacks of previous methods by ensuring consistent pore size and interconnectivity.
Implementation Method 1
immersing the shaped article in an immersing liquid in which the polymer particles are soluble, for a period of time of from about 10 minutes to about two weeks to dissolve the polymer particles in the immersing liquid, thereby creating pores in the shaped article
Data Source
AI summary
A method for making a porous, chemically bonded ceramic shaped article comprises i) providing a precursor powder mixture comprising polymer particles and a ceramic self-setting cementitious powder; ii) preparing a shaped article from a paste comprising the precursor powder mixture and an aqueous liquid; and iii) immersing the shaped article in an immersing liquid in which the polymer particles are soluble, for a period of time of from about 10 minutes to about two weeks to dissolve the polymer particles in the immersing liquid, thereby creating pores in the shaped article. A porous, chemically bonded ceramic shaped article having interconnected pores, a total porosity of at least about 50%, and a macroporosity of at least about 30% can be formed by such methods.