Programmable Wrinkling of Self-Assembled Nanoparticle Films on Shape Memory Polymers

Abstract

Hierarchically structured materials, inspired by sophisticated structures found in nature, are finding increasing applications in a variety of fields. Here, we describe the fabrication of wrinkled gold nanoparticle films, which leverage the structural tunability of gold nanoparticles to program the wavelength and amplitude of gold wrinkles. We have carefully examined the structural evolution and tuning of these wrinkled surfaces through varying nanoparticle parameters (diameter, number of layers, density) and substrate parameters (number of axes constrained during wrinkling) through scanning electron microscopy and cross-sectional transmission electron microscopy. It is found that nanoparticle layers of sufficient density are required to obtain periodical wrinkled structures. It was also found that tuning the nanoparticle diameter and number of layers can be used to program the wrinkle wavelength and amplitude by changing the film thickness and mechanical properties. This dual degree of tunability, not previously seen with continuous films, allows us to develop one of the smallest wrinkles developed to date with tunability in the sub-100 nm regime. The effect of the induced structural tunability on the enhancement of the intensity of the 4-mercaptopyridine Raman spectra is also studied through the application of these devices as substrates for surface-enhanced Raman spectroscopy (SERS), where wrinkling proves to be an effective method for enhancing the SERS signal in cases where there is an inherently low density of gold nanoparticles.

Controlled evolution of surface patterns for ZnO coated on stretched PMMA upon thermal and solvent treatments

“…Subsequently, the resulting wrinkles are randomly distributed (as shown in Fig. 3 (b)) [11,41,48,49]. The wrinkling mechanism owing to thermal expansion mismatch between ZnO film and PMMA substrate is illustrated in Fig.…”

“…The mechanisms for producing surface patterns include wrinkling, creasing, cracking, and buckling [6][7][8][9][10][11]. Wrinkling is one of the surface buckling phenomena, which is conventionally generated in bi-layer structures consisted of a thin metallic layer and a polymer substrate.…”

Functional Micro–Nano Structure with Variable Colour: Applications for Anti-Counterfeiting

“…Spraying, atomizing, spin coating, dispensing e self-assembly of biomimetic isotropic films are achieved with a characteristic length-scale comparable to the wavelength of visible light [120] Self-assembled photonic crystals by magnetic field force Magnetic particles and nanospheres (silica [121], polystyrene [122], carbon [123], polyvinylpyrrolidone [124], polyacrylamide [125]) Monodisperse microspheres self-assemble into ordered structures under the action of a magnetic field e self-assembly process is reversible, and the band gap position can also be adjusted by controlling the strength of the magnetic field Self-assembled photonic crystals by gravity Monodisperse microspheres with higher density such as silica [126] Colloidal particles are free to settle and self-assemble into an ordered structure in constant temperature, humidity and vapor pressure environment [127] e photonic crystal obtained by the gravity is difficult to control and is prone to defects [131] Electron beam etching PMMA (positive rubber) and SU-8 (negative rubber) materials [132] Polymer in the region exposed to the electron beam will undergo a soluble change, and the micro-nano structure can be obtained by the developer ere is no need to contact the surface of the material, the deformation is small under stress, and the pollution is less, and the surface of the material is not [86] or ultraviolet irradiation [84,85] e resolution is not affected by the most exposed wavelength, and is closely related to the original template resolution. It has high fidelity, high resolution, low cost and high yield Surface wrinkle technology PDMS [134], polystyrene [135] and shape memory materials [136][137][138][139] are used as base materials, organic polymer materials [140], metal materials [141], and inorganic materials [142] can be used as surface hard layer materials Surface instability factors are induced by heat, force, electromagnetic field, humidity, phase separation, osmotic pressure, capillary force and polymerization…”

Bench-Top Fabrication of an All-PDMS Microfluidic Electrochemical Cell Sensor Integrating Micro/Nanostructured Electrodes

“…Recently, SMPs have gained significant traction in the microfabrication community for their ability to produce 3D micro/nanostructured surfaces on a variety of thin films (e.g., Au, Pt, CNT, SiO 2 , and TiO 2 ) [13,20,30,31,32,33,34,35]. The structured surfaces are produced through a compressive stress applied by the SMP during shrinking once it is heated over its glass transition temperature [21,36].…”