Mechanical Design of Biomedical Products Using Plastics

Biomedical products typically have physical requirements that differ in some respects from other products. Those requirements usually center on the need for materials and configurations that are compatible with the human body. Not only are such products regulated by FDA requirements, but they must also be able to withstand multiple sterilization cycles involving high temperatures or the use of solvents, or both.

To design parts in the biomedical industry it is necessary to understand the properties of biomedical safe materials, and to understand the constraints on processing those materials to produce sound and economical parts. Not all injection molding factories have both the capability and experience to mold these materials. As an example, parts have been designed and molded both domestically and abroad using Lexan HP2NR and Lexan HPX4. Both of these are FDA approved biocompatibility tested (FDA USP Class VI/ISO10993) plastics.

Lexan HP2NR is clear Polycarbonate plastic. 121C autoclavable for a handful of cycles. As an example, this material is being utilized in a lens for a product used for skin care treatment. The molding resource has been able to mold this material at almost defect free levels in the past 2 years. Lexan HPX4 is a Siloxane copolymer. It performs better in autoclave at 121C (a few dozen cycles, again depends on in-mold stress, morpholine level in autoclave etc. It has a slight haze in its natural state. An example of a biomedical application of this material is a part being colored with FDA approved dye to a gray Pantone 430C color when molded on an oral device used by sleep apnea patients. After molding, the parts go through a thermal press process that creates 300+ features necessary for the retention of the epoxy applied by the user. Parts are thoroughly cleaned in isopropyl alcohol solution, heat dried then bagged and boxed for shipment.

In addition to understanding the issues relating to the materials employed in designing and producing biomedical products it is also necessary to have a good grasp on ergonomic principles and the ability to apply those principles in design. Ergonomics is defined as the study of designing equipment and devices that fit the human body, its movements, and its cognitive abilities. It is always good to consider ergonomics in product design, but in the biomedical arena it is usually critical to the success of the product.

In summary, a successful biomedical product development should be characterized by carefully considered selection of materials and the capability to properly process those materials. Additionally, biomedical product development should also consider a strong dedication to ergonomic principles.

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