Polymer substrates break through the limitations of rigid planar substrates in spatial deformation scenarios and can be combined with photolithography to fabricate complex, three-dimensional irregular polymer structures. Photothermal-shock tweezer is a laser trapping technique based on the photothermal shock effect. Photothermal-shock tweezer uses pulsed laser induced transient photothermal shock to generate micro-newton-scale thermomechanical strain gradient force, enabling the trapping and manipulation of micro/nano-objects at solid interfaces. Integrating this technique with polymer substrates can meet the demands of new application scenarios. In this work, commonly employed polymethyl methacrylate (PMMA) and negative photoresist (SU-8) are used as polymer substrates, on which SiO₂ nanofilms are prepared using the sol-gel method. This method effectively mitigates thermal damage caused by photothermal shock effects, enabling laser trapping and manipulation of micro/nano-objects.

The SiO₂ nanofilms, characterized by low thermal conductivity, effectively inhibit heat transfer. The nanofilm fabrication technique utilized in this study enables the synthesizing of large-area SiO₂ nanofilms with large-area coverage, low surface roughness (R_q ~ 320 pm) and uniform thickness, making them broadly applicable to flexible polymer substrates and irregular structures. Direct contact between the polymer layer and micro/nano-objects during manipulating the photothermal shock tweezer can induce irreversible substrate degradation due to transient photothermal shock effects. Experimental results demonstrate that depositing an SiO₂ nanofilm thicker than 110 nm on the polymer substrate can significantly enhance thermal insulation and protection, effectively mitigating laser-induced damage under typical optical manipulation conditions.

Additionally, by analyzing the temperature field distribution of the gold nanosheet, PMMA substrate, and SiO₂ nanofilm during a single photothermal shock trapping of a gold nanosheet, it is found that the SiO₂ nanofilm can reduce the PMMA surface temperature by at least 111 ℃ and delay the time for PMMA to reach its peak temperature by 13.2 ns compared with the the gold nanosheet. The experimental results expand the environmental medium for laser trapping of objects, providing new possibilities for applications in micro/nano-manipulation, micro/nanorobotics, and micro/nano-optoelectronic devices.