Solid-State Dewetting of Gold on Stochastically Periodic SiO2 Nanocolumns Prepared by Oblique Angle Deposition

Dewetting Process of Silver Thin Films and Its Application on Percolative Pressure Sensors with High Sensitivity

This work reports on an innovative dewetting process of silver thin films to realize percolative nanoparticle arrays (NPAs) and demonstrates its application on highly sensitive pressure sensors. The dewetting process, which is a simple and promising technique, synthesizes NPAs by breaking the as-deposited metal film into randomly distributed islands. The NPA properties, such as the mean particle size and the spacing between adjacent particles, can be easily tailored by controlling the dewetting temperature, as well as the as-deposited metal-film thickness. The fabricated NPAs were employed to develop gauge pressure sensors with high sensitivity. The proposed sensor consists of a sealed reference-pressure cavity, a polyimide (PI) membrane patterned with an interdigital electrode pair (IEP), and a silver NPA deposited on the IEP and the PI membrane. The operational principle of the device is based on the NPA percolation effect with deformation-dependence. The fabricated sensors exhibit rapid responses and excellent linearity at around 1 atm. The maximum sensitivity is about 0.1 kPa^-1. The advantages of the proposed devices include ultrahigh sensitivity, a reduced thermal disturbance, and a decreased power consumption. A practical application of this pressure sensor with high resolution was demonstrated by using it to measure the relative floor height of a building.

Elucidating Sensitivity and Stability Relationship of Gold-Carbon Hybrid LSPR Sensors Using Principal Component Analysis

Sensitive localized surface plasmon resonance (LSPR) sensing is achieved using nanostructured geometries of noble metals which typically have dimensions less than 100 nm. Among the plethora of geometries and materials, the spherical geometries of gold (Au) are widely used to develop sensitive bio/chemical sensors due to ease of manufacturing and biofunctionlization. One major limitation of spherical-shaped geometries of Au, used for LSPR sensing, is their low refractive index (RI) sensitivity which is commonly addressed by adding another material to the Au nanostructures. However, the process of addition of new material on Au nanostructures, while retaining the LSPR of Au, often comes with a trade-off which is associated with the instability of the developed composite, especially in harsh chemical environments. Addressing this challenge, we develop a Au-graphene-layered hybrid (Au-G) with high stability (studied up to 2 weeks here) and enhanced RI sensitivity (a maximum of 180.1 nm/RIU) for generic LSPR sensing applications using spherical Au nanostructures in harsh chemical environments, involving organic solvents. Additionally, by virtue of principal component analysis, we correlate stability and sensitivity of the developed system. The relationship suggests that the shelf life of the material is proportional to its sensitivity, while the stability of the sensor during the measurement in liquid environment decreases when the sensitivity of the material is increased. Though we uncover this relationship for the LSPR sensor, it remains evasive to explore similar relationships within other optical and electrochemical transduction techniques. Therefore, our work serves as a benchmark report in understanding/establishing new correlations between sensing parameters.