Rational design of wettability-patterned microchips for high-performance attomolar surface-enhanced Raman detection

Xue-Song Shi; Yu-Fan Zhao; Hong-Ye Zhang; Xue-Feng Xu

doi:10.1016/j.talanta.2023.124417

Rational design of wettability-patterned microchips for high-performance attomolar surface-enhanced Raman detection

Talanta. 2023 Jun 1:258:124417. doi: 10.1016/j.talanta.2023.124417. Epub 2023 Mar 6.

Authors

Xue-Song Shi¹, Yu-Fan Zhao², Hong-Ye Zhang², Xue-Feng Xu²

Affiliations

¹ School of Technology, Beijing Forestry University, Beijing, 100083, PR China. Electronic address: shixuesong@bjfu.edu.cn.
² School of Technology, Beijing Forestry University, Beijing, 100083, PR China.

PMID: 36931060
DOI: 10.1016/j.talanta.2023.124417

Abstract

Recent progress in wettability-patterned microchips has facilitated the development of ultra-trace detection in multiple biomedical and food safety fields. The existence of a superhydrophilic trap can realize targeted deposition of the analyte. However, the wetting transition from the Cassie-Baxter state to the Wenzel state usually occurs during evaporation and leads to a larger deposition footprint, which has a strong impact on the detection sensitivity and uniformity. In this paper, we report an integrated design, fabrication, and evaporation strategy to avoid the transition for high-performance attomolar surface-enhanced Raman scattering (SERS) detection. An improved force balance model was proposed to design the microstructures of wettability-patterned microchips, which were fabricated by nanosecond laser direct writing and surface fluorination. The microchips were composed of superhydrophobic micro-grooves and superhydrophilic traps, by which the targeted deposition of Au nanoparticles and rhodamine 6G (R6G) onto a minimal area of ∼70 × 70 μm² was realized after a two-step heated evaporation. Accordingly, the detection limit was down to the attomolar level (5 × 10^-18 M) with SERS enhancement factors (EFs) exceeding 10¹⁰. More importantly, the Raman signals showed good uniformity (RSD of 11.5%) for the concentration of 2 × 10^-17 M. A good linear relationship was obtained in the quantitative concentration range of 10^-12 M to 5 × 10^-18 M with a high correlation coefficient (R2) of 0.996. These wettability-patterned microchips exhibit high performance (that is, both good sensitivity and good uniformity) in the detection of ultra-trace molecules in aqueous solutions, avoiding the need for expensive equipment and considerable skill in operations. The proposed strategy could also be applied to other microfluidic devices for rapid and simple analyte pre-concentration.

Keywords: Droplet evaporation; Surface-enhanced Raman scattering (SERS); Ultra-trace detection; Wettability-patterned surface; Wetting transition.