They look simple but disposable or single-use medical devices require an careful balance between performance, cost, reliability, materials, and shelf life.

You might forgive a newly minted engineer for thinking the dominant factor in the design of a single-use product is cost. Although disposables work a short shift, designing them starts by listing and understanding user requirements, and then balancing performance, cost, reliability, materials, and shelf life. Then it entails developing an efficient, repeatable manufacturing process.

Designing for end use

True, user requirements drive product specifications, but there is more than that. Cost is a significant factor because most disposable products function only once. There is no potential to minimize costs with repeated use. Current technology can help speed product development and keep costs down. And, the device must meet strict requirements set forth by the Food and Drug Administration, as well as work reliably and consistently.

To create a high-quality product, designers must recognize and mitigate risks associated with disposable devices. Risks in this discussion fall into three categories: risk of design, risk of process, and risk of use.

Injection molding and a broad range of useful plastics have been effective holding down costs on disposable medical products. But like all manufacture operations, it introduces some risk of process that must be accounted for in the design cycle.

Risk of design prevents problems from the outset. Failure Mode and Effects Analysis (FMEA) is one design tool that helps pinpoint risks. Failures are any errors or defects, especially ones that affect the customer. Failure modes are characterizations of the ways a product or process can fail. Effect analysis refers to studying the consequences of those failures.

In FMEA, failures are prioritized according to seriousness of consequences, frequency and ability to detect. The method also documents current knowledge and actions about the risks of failures for use in continuous improvement. FMEA is used during design stage to prevent failures. Later in the product lifecycle it is used for process control. It can be used to create risk management priorities, helping to select remedial actions that reduce cumulative impacts of risks.

Risk of process encompasses how the product is made, and includes materials, machines and equipment, environment, personnel, methods, and a management system.

Risk of use looks for problems that may crop up in the field, and how product design can prevent them. Identifying product risks helps ensure development of a repeatable manufacturing operation.

Meeting design requirements calls for gathering as much information as possible at early stages of product development. This is done with a cross-functional team consisting of several departments such as research and development, packaging, sterilization, manufacturing, marketing, quality and regulatory. The different viewpoints expressed by team members help minimize or eliminate product development complications. This in turn minimizes product scope changes, which reins in costs.