Reusable Surface-Enhanced Raman Spectroscopy Membranes and Textiles via Template-Assisted Self-Assembly and Micro-/Nano-Imprinting

The development of wearable sensors for continuous real-time monitoring of human physiological status has attracted extensive research efforts. While significant commercial success has been made in wearable physical sensors for monitoring physiological parameters like heart rate and body temperature, wearable chemical sensors are still under intense research and development for applications in personal health management, including body biofluids analysis, wound monitoring, and human-centered environmental sensing of hazardous chemicals. Surface-enhanced Raman spectroscopy (SERS) has emerged as a powerful tool for ultrasensitive fingerprint recognition of molecules with considerable potential in wearable biochemical sensing. However, previous efforts to fabricate wearable SERS devices by directly treating fabrics with plasmonic nanoparticles have generated a nonuniform assembly of nanoparticles, weakly adsorbed on fabrics via van der Waals forces. Here, we report the creation of washing reusable SERS membranes and textiles via template-assisted self-assembly and micro-/nano-imprinting approaches. Uniquely, we employ a capillary force-driven self-assembly process to generate micropatch arrays of Au nanoparticle (NP) aggregates within hydrophobic microstructured templates, which are then robustly bonded onto semipermeable transparent membranes and stretchable textiles using a UV-resist based micro/nanoimprinting technique. Compared to previously developed wearable SERS devices, our fabrication technique offers several advantages: (1) good uniformity control of the spatial distribution and intensity of SERS hotspots, (2) good manufacturing compatibility with many types of delicate membrane/fabric materials due to the mild UV micro/nanoimprinting process at room temperature, and (3) strong mechanical bonding between Au NPs and the wearable substrates via a UV-cured resist. Due to the good mechanical robustness of the UV-resist immobilized Au NP aggregates, we could regenerate contaminated SERS hotspots using user-friendly detergent-water washing processes over multiple cleaning cycles without degrading the sensing performance. Moreover, we demonstrate that substituting conventional UV-resists with carbon nanotube-polymer composite resists can generate conductive wearable SERS devices, enabling electrochemical SERS for improved sensitivity and selectivity of detection in multi-analyte systems. Therefore, we envision that the template-assisted self-assembly and micro-/nano-imprinting approaches can help create wearable washing reusable SERS fabrics/membranes with advanced materials properties via polymer nanocomposites for specific needs in different biochemical sensing applications.