Flexible SERS sensing substrate for highly sensitive detection and in-situ detection of Hazardous substances

Surface-enhanced Raman scattering (SERS) has emerged as a powerful technique for the detection of ultralow concentration molecules. Flexible SERS substrates, in contrast to their rigid counterparts, offer unique merits, leading to their broad applications in point of care diagnosis, food safety assessment, and environmental monitoring. In this work, we exploited the outstanding micro-nano structure processing capabilities of femtosecond lasers to precisely engineer the surface structure of materials. By integrating periodic superhydrophobic structure with hydrophobicity of polydimethylsiloxane (PDMS), we achieved the stable fixation of droplets at designated positions. This configuration effectively concentrated target detection molecules within a 400 μm diameter hydrophobic region. Notably, employing microliter scale samples, we successfully achieved sensitive detection at femtomolar level (10⁻¹⁶ M) with relatively stable performance. Leveraging the remarkable flexibility of PDMS, the flexible substrate can be used to sample from complex curved surfaces, enabling in-situ detection of sweat components and pesticide residues on vegetable surfaces. The limit of detection for thiram on eggplant surfaces is 10 ppb. This research presents a novel method for fabricating flexible SERS substrates with high detection sensitivity, which hold great potential for various practical applications.