Simultaneous Curing and Monitoring of Resin Using GaN Chips

In this letter, a novel approach is proposed for simultaneous curing and monitoring of resin using miniature GaN chips. Three GaN-on-sapphire devices operating in the blue-green visible spectrum provide light emission and detection functions. The flip-chip bonding configuration enables the emitted light to be coupled to the resin through the transparent sapphire substrate without relying on external optics. The change in the refractive index of resin during the curing process adjusts the reflectance at the sapphire/resin boundary, which can be monitored by the on-chip detector. Fabricated through scalable, controllable, and low-cost microfabrication processes, the proposed chip-scale devices are highly compact, robust, and easy to operate, making them appealing candidates for practical applications requiring in situ monitoring of the curing process.