Biodegradable Magnesium Alloy Implants Corrosion Control
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Solution Overview
Problem
Current metallic implant devices used in orthopedic, craniofacial, and cardiovascular applications do not degrade over time, leading to complications such as stress-shielding effects, immune responses, and the need for additional surgeries to remove them, while biodegradable alternatives like magnesium alloys face issues with corrosion and hydrogen gas accumulation.
Innovation Solution
Development of biodegradable metal alloy compositions containing magnesium with added elements like yttrium, calcium, and zirconium to control corrosion rates and improve mechanical properties, ensuring the implants degrade harmlessly and do not remain in the body post-healing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If permanent metallic implant devices (stainless steel, Co-Cr, titanium alloys) are used, then high strength and corrosion resistance are achieved, but the implants do not degrade over time requiring additional surgery for removal
Solution Approach 1:
The patent changes the chemical composition parameters of magnesium alloys by adding specific elements (Yttrium: 0.1-5.0 wt%, Calcium: 0.1-5.0 wt%, Zirconium: 0.1-3.0 wt%, Zinc: 1.0-10.0 wt%) to control degradation rate while maintaining mechanical strength. This allows the implant to degrade at a controlled rate matching bone healing, resolving the contradiction between strength and degradation time
Solution Approach 2:
The patent creates composite magnesium-based alloys combining multiple elements to achieve synergistic effects. The composite structure provides both the biodegradability of magnesium and the enhanced strength/corrosion resistance from alloying elements, enabling controlled degradation while maintaining adequate mechanical properties during the healing period
2Duration of action of moving object
If biodegradable materials (polymers like PLA, PGA) are used, then degradation and dissolution in physiological environment are achieved, but relatively poor strength and ductility are exhibited
Solution Approach 1:
The patent substitutes polymer materials with magnesium-based metal alloys. Magnesium provides superior mechanical properties (strength, ductility, toughness) compared to polymers while maintaining biodegradability. The metal alloy degrades through controlled corrosion rather than polymer chain scission, preserving mechanical integrity longer during the critical healing period
3Duration of action of moving object
If magnesium alloys are used for biodegradability, then degradation in physiological environment is achieved, but accelerated corrosion and hydrogen gas accumulation occur
Solution Approach 1:
The patent introduces intermediary alloying elements (Yttrium, Zirconium, Calcium) that mediate the corrosion process. These elements form protective surface films and modify the corrosion mechanism to reduce hydrogen evolution rate. Yttrium and Zirconium specifically enhance surface passivation, acting as intermediaries between magnesium and the physiological environment to control harmful hydrogen gas generation
Solution Approach 2:
The patent converts the naturally rapid corrosion of magnesium from a harmful feature into a beneficial controlled degradation process. By adding alloying elements, the rapid corrosion is transformed into controlled, uniform degradation that releases ions beneficial for bone healing while minimizing hydrogen gas accumulation through modified corrosion mechanisms
4Strength
If current metallic biomaterials (stainless steel, Ti, Co-Cr alloys) are used, then high strength and rigidity are achieved, but stress-shielding effects occur reducing bone loading and growth
Solution Approach 1:
The patent changes the mechanical properties of the implant material by using magnesium-based alloys with tunable strength (200-500 MPa ultimate tensile strength) and elastic modulus closer to bone. This allows the implant to provide adequate support while gradually transferring load to the healing bone, eliminating stress-shielding effects that occur with stiffer permanent metals
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 biodegradable metal alloy compositions provide improved corrosion resistance and mechanical strength, reducing the risk of hydrogen gas accumulation and allowing for safe degradation of implants, addressing the limitations of existing materials.
Implementation Method 1
biodegradable metal alloy compositions...degrade over time...dissolve in a physiological environment
Implementation Method 2
control corrosion rates...yttrium, calcium, and zirconium
Data Source
AI summary
The invention relates to biodegradable, metal alloy-containing compositions, methods for their preparation and applications for their use. The compositions include magnesium and other components, such as yttrium, calcium, silver, cerium, and zirconium; or zinc, silver, cerium, and zirconium; or aluminum, zinc, calcium, manganese, silver, yttrium; or strontium, calcium, zinc. The compositions are prepared by vacuum induction/crucible melting together the components and casting the melted mixture in a preheated mild steel/copper mold. In certain embodiments, the compositions of the invention are particularly useful for forming medical devices for implantation into a body of a patient.