Synthesis of Tunable Core-Shell Based Thermal Switch via 'Endocytosis' Process.

Triggered rupture in core-shell capsules is particularly attractive for applications that require rapid response, irreversible operation, or high instantaneous output, such as burst release and catalytic processes. In most existing designs, however, both rupture activation and threshold tuning rely on stimuli-responsive materials, which increases fabrication complexity and makes the triggering temperature largely dependent on the intrinsic thermal response of the chosen material. Here, we show that the thermal rupture threshold of sealed liquid-core capsules can be programmed through capsule geometry without incorporating thermoresponsive additives. Pentaerythritol triacrylate (PETA)-paraffin capsules with systematically varied core-shell geometries are fabricated using an endocytosis-like droplet-impact route. Thermal loading induces internal pressurization within the confined core, and rupture occurs when the resulting shell stress exceeds the load-bearing capacity of the shell. Experimental results and theoretical analysis support a pressure-driven rupture mechanism and explain the geometry dependence of the triggering threshold. As a simple demonstration, capsule rupture is used to actuate an electrical switch, illustrating its potential as a one-shot thermal response unit. This work establishes a structure-driven route to programmed thermal rupture in capsules and highlights geometric confinement as a design principle for rupture-based systems.