Continuous Preparation of Core‐Shell Capsules for CO ₂  Detection Using Photosensitive Polymeric Resins

Core–shell CO 2 ‐detector capsules were developed using a cost‐effective, energy‐efficient, and scalable production method. The polymer capsules consisted of liquid potassium carbonate cores and highly permeable UV‐curable acrylate resin shells, were fabricated through a continuous injection process, and allowed rapid and controlled CO 2 uptake and release during repeated absorption–desorption cycles while maintaining the capacity and selectivity of liquid sorbents with a high surface area to volume ratio. A custom UV box was employed as an innovative curing system to ensure uniform capsule formation. The capsules produced under these conditions exhibited an outer diameter of 2.95–3.10 mm and a shell thickness of 0.09–0.37 mm. During CO 2 exposure, the capsules demonstrated reversible absorption–desorption behavior and after approximately 100 s, a visible color transition from blue to yellow occurred due to a pH decrease in the core caused by CO 2 absorption. Also, when capsules were placed under vacuum, the reaction was reversed and they regenerated, returning to their original blue color. The developed method offered a simple and scalable alternative to conventional microfluidic encapsulation, producing uniform capsules with fast response and easy regeneration which are suitable for low‐cost and reusable optical CO 2 sensors.