The routinization of lay expertise: A diachronic account of the invention and stabilization of an open-source artificial pancreas.

Embodied health movements (EHMs) advance their agendas by mediating the production, circulation, and revision of biomedical knowledge. To do this, their constituents become lay experts by blending their embodied experience of illness with self-taught technical knowledge. However, it is unclear how lay expertise is routinized within EHMs, and consequently, to what extent it can be made durable in long-term partnerships with credentialed experts. I follow the OpenAPS community-a group of people with type one diabetes who engineered an open-source 'artificial pancreas'-from their inception in the transient #WeAreNotWaiting movement to their research collaborations with endocrinologists and detente with the FDA. I argue that OpenAPS user-contributors formalized their expertise in three steps: First, they broke the OpenAPS algorithm into modules so that prospective users must become experts to assemble it. Second, they lowered this barrier to entry by facilitating the socialization of new user-contributors with a training ritual. And third, they intervened in the strained endocrinologist-patient relationship. These tactics-restricting membership, reproducing expertise, and realigning interests-won the respect of credentialled experts who saw themselves in the OpenAPS community's image. While not all EHMs follow this trajectory, this case demonstrates that lay expertise can mature and assume new institutional forms without relying on commercialization or patronage.