Nanosecond Laser Debonding Using an Ultrathin Absorber Layer in a Transparent Composite: Making a Light‐Powered Exploding Bolt.

Localized heating of an adhesive interface can separate glued substrates for recycling or reconfiguring. Light provides a way to deposit energy at this type of buried interface, but the photon energy must still be transformed into thermal energy. The deposition of an ultrathin (<1 µm) absorbing layer before gluing provides a way to build this photothermal capability into the bonded structure. To demonstrate this concept, a submicron absorbing layer composed of the dye Fluorescein 27 (F27) is applied to a poly(methyl methacrylate) (PMMA) substrate that is glued to a second PMMA piece using a commercial cyanoacrylate adhesive. The laser debonding is characterized as function of dye layer thickness, applied pressure, and laser pulse fluence. A 450 nm thick dye layer retained a high adhesive strength of 3.5 MPa but can be debonded by a single 532 nm nanosecond laser pulse with a fluence ≤ 0.7 J cm−2. Decomposition of the absorbing layer resulted in rapid gas evolution that left the micron‐scale surface morphology of the PMMA substrate intact. This system enabled the fabrication of an optical analog to the exploding bolt, where a single laser pulse can impulsively separate a structural fastener. [ABSTRACT FROM AUTHOR]