3-Functionability:
The functionability of a medical device depends on the ability of the material to be shaped to suit a particular function. The material must therefore be able to be shaped economically using engineering fabrication processes. The success of the coronary artery stent - which has been considered the most widely used medical device — can be attributed to the efficient fabrication process of stainless steel from heat treatment to cold working to improve its durability.
4 -Manufacturability:
It is often said that there are many candidate materials that are biocompatible. However it is often the last step, the manufacturability of the material, that hinders the actual production of the medical device.
Performance of Biomaterials:
The success of biomaterials in the body depends on factors such as the material properties, design, and biocompatibility of the material used, as well as other factors not under the control of the engineer, including the technique used by the surgeon, the health and condition of the patient, and the activities of the patient. If we can assign a numerical value f to the probability of failure of an implant, then the reliability can be expressed as:
r = 1 ? f
If, as is usually the case, there are multiple modes of failure, the total reliability rt is given by the product of the individual reliabilities r1 = (1 ? f1), etc.
rt = r1 • r2 • • • rn
Consequently, even if one failure mode such as implant fracture is perfectly controlled so that the corresponding reliability is unity, other failure modes such as infection could severely limit the utility represented by the total reliability of the implant. One mode of failure which can occur in a biomaterial, but not in engineering materials used in other contexts, is an attack by the body’s immune system on the implant.
Another such failure mode is an unwanted effect of the implant upon the body; for example, toxicity, inducing allergic reactions, or causing cancer.
Surface Modifications for Improving Biocompatability:
Prevention of thrombus formation is important in clinical applications where blood is in contact such as hemodialysis membranes and tubes, artificial heart and heart–lung machines, prosthetic valves, and artificial vascular grafts. In spite of the use of anticoagulants, considerable platelet deposition and thrombus formation take place on the artificial surfaces.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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