On-demand manufacture of circular 3D-printable resins.

Recent progress in circular 3D-printable photocurable resins that enable closed-loop recycling marks a significant step forward in reducing wasteful manufacturing methods and non-recyclable printed plastics. However, with 3D printing technologies shifting from prototyping to full-scale production, the demand for high-scale processes and easily tuneable resin compositions can benefit from the design of automated systems. Herein, we report on the on-demand preparation of a circular 3D-printable resin, achieved through a continuous flow approach. A supported enzyme (Lipase B from Candida antarctica) was used to promote a green esterification of the lipoic acid with biobased alcohols to prepare circular biobased photocurable resins. The supported enzyme was employed for the preparation of a packed bed reactor and was easily recycled and reused to achieve the continuous production of lipoate-based photocurable resins with tuneable composition. Lastly, the environmental impact of the developed on-demand manufacturing process was compared to the previously reported esterification protocols through life cycle assessment, showing the effectiveness of continuous enzymatic flow synthesis in enhancing environmental performance across multiple areas, from human health to ecosystem impact and resources.