We report a one‑step direct laser writing (DLW) approach that metallizes polydimethylsiloxane (PDMS) with conductive copper patterns from deep eutectic solvent (DES) inks under ambient conditions, without compromising the inherent mechanical or optical properties of the substrate. The underlying patterning mechanism is confirmed by thermal modeling and experimental validation, with particular emphasis on the influence of substrate thermophysical properties and DES layer thickness on the metallization process. Under optimized conditions, copper patterns with resistivity as low as 2.25 × 10-³ Ω·cm can be fabricated while maintaining excellent mechanical durability under repeated bending deformation. Functional performance is demonstrated by integrating the deposited copper patterns into flexible heaters and LED circuits. These results establish DES-enabled direct laser writing as a scalable and environmentally friendly platform for fabrication of soft electronic devices.