"Medical equipment" is a broad term, covering a variety of instruments and equipment, such as band aids, dental floss, blood pressure cuff, defibrillator, nuclear magnetic resonance scanner, etc. Medical device design is an important part of mechanical engineering.
The development process of a medical device is no different from that of any other device: design, prototyping, testing, and replication. However, medical equipment has more stringent requirements for materials. Due to the requirements of testing and clinical trials, many medical device prototypes require biocompatible or sterilizable materials.
1. Biocompatible materials
For plastics, the most stringent requirement is USP level 6 test. USP level 6 testing involves three in vivo biological reactivity assessments on animals, including:
acute systemic toxicity test: this test measures the irritation effect of oral administration, skin application and inhalation of samples.
intradermal test: this test measures the stimulation effect when the sample contacts with the living subdermal tissue.
implantation test: this test measures the stimulation effect of implanting the sample muscle into the test animal within five days.
3D printing can produce almost all geometry, which is very useful for fast iteration of complex design. CNC processing is applicable to the prototyping and end use production of medical device parts. There are more materials to choose from, and the materials are stronger.
However, the design needs more attention to ensure machinability.
The following materials are certified by USP level 6 test: POM, PP, Pei, peek, PSU, PPSU
If you are making prototypes that will not be used in the early stages of experiments or clinical trials, consider using non certified plastics. You can get the same mechanical performance without paying a higher price. POM 150 is an excellent material for early prototyping.
CNC machining can also produce biocompatible metal parts. There are three common implant grade options:
stainless steel 316L
titanium grade 5, also known as Ti6Al4V or ti6-4
cobalt chromium alloy (CoCr)
Stainless steel 316L is the most commonly used material among the three materials. Titanium has a better weight strength ratio but is much more expensive. CoCr is mainly used for orthopedic implants. We recommend that you use SS 316L for prototyping when improving the design, and then use more expensive materials when the design is more mature.
2. Sterilizable materials
Any reusable medical device that may come into contact with blood or body fluid must be sterilized. Therefore, most medical devices used in medical facilities are made of sterilizable materials. There are many sterilization methods: heating (dry heat or autoclave / steam), pressure, chemicals, irradiation, etc.
