Bending‐Insensitive Flexible SERS Sensor for Stable and Sensitive Detection on Curved Surfaces

Abstract

Flexible sensing technologies are an essential link to future on-site and real-time monitoring technologies and devices in diverse fields, including healthcare, environment, medicine, food safety, biology, and so on. Compared to rigid substrate-based detection, the flexible sensing technique, which relies on the materials with soft and flexible features, provides intimate contact with arbitrary surfaces for on-site detection, especially in resource-limited environments. It can omit complicated extraction of analytes of interest and tedious sample preparation steps prior to detection, which is not suitable for practical applications. In particular, they are of great and continuous interest in medical diagnostics since they can provide noninvasive and real-time insight into the physiological signals of the human body, which is vital for more accurate diagnosis or tailoring therapy to maintain optimal health. These flexible biosensors can save healthcare time and costs, eventually aiming for personalized precision medicine. [1] Among the various flexible biosensors, surface-enhanced Raman scattering (SERS) has attracted enormous research attention because it provides a noninvasive, label-free, and molecular specific route for the recognition of a wide range of molecules with superb sensitivity. In SERS, the enormous electromagnetic signal enhancement is induced by the plasmonic coupling effect at a few nanometer-sized small space between metal nanostructures, so called "hot-spots". [2] Important prerequisites for flexible sensors are that they should produce a uniform signal regardless of bending that accompanies on-body usage, as well as present high signal enhancement and be resilient to mechanical strains. Although, the curvature of a person's waist, wrist, and thigh differs, a wearable sensor should exhibit uniform detection efficacy. However, most of the earlier flexible SERS strategies have created hot-spots between metal nanostructures on the surface of their backbone and attempted to locate target molecules inside the electromagnetic field concentrated region. In this case, the distance between the nanostructures on the flexible sensor was changed by bending the flexible sensor. This variance severely deteriorates the signal uniformity of the SERS sensor since the magnitude of hot-spots is extremely dependent on the distance between the metal nanostructures. [3] Surface-enhanced Raman scattering (SERS) based flexible sensing technology has been considered an essential candidate for future diagnostics in diverse fields. To obtain a reliable signal from the flexible SERS sensor, signal reproducibility even when the substrates are bent is highly desirable because there are various curvatures in the practical applications. However, this remains challenging because the "hot-spots" were created between the individual nanostructures on the surface of the previous flexible SERS sensor. The distance between each nanostructure varied through the bending of the sensor, leading to an adverse effect on the unform ...

Curvature-Insensitive Transparent Surface-Enhanced Raman Scattering Substrate Based on Large-Area Ag Nanoparticle-Coated Wrinkled Polystyrene/Polydimethylsiloxane Film for Reliable In Situ Detection

“…Therefore, there is an urgent demand for a simple, efficient, and affordable technology that can create structured 3D features on large-scale PDMS films. Moreover, for flexible sensors to be used in daily applications, they must consistently generate a uniform signal regardless of the bending of the underlying substrates [ 34 ]. Additionally, these sensors should exhibit high signal enhancement.…”