The cost per part to increase the safety of the Pinto, they calculated at $11.00 per part.

能增加平托安全性的隔板，每块成本是11美元。

耶鲁公开课 - 公正课程节选

So they have to be engineered to be inert so that they can be safely inside a system and there's not every material you could pick would have that property.

缝合线必须是惰性的,以便确保植入人体后的安全性,不是随便哪个材料都能做到这一点

耶鲁公开课 - 生物医学工程探索课程节选