Chameleons have nanostructures in their skin that interact with light to create structural color. When the spacing between these nanostructures is changed, the light-matter interactions change. This is one of the mechanisms that allow chameleons to manipulate their color.
 
Inspired by chameleons, I have been researching the optical properties of hemiellipsoidal nanopillar arrays, hoping to contribute fundamental understanding of structural color for applications such as colorimetric strain sensing. 
Before conducting novel research, I trained in two-photon lithography in order to create 3D nanostructures of arbitrary shapes. In my first phase of novel research, I developed fabrication processes for flexible and precise 3D nanostructures. In my second phase of novel research, I developed fabrication processes to incorporate silver nanoparticles into these flexible nanostructures in the hopes of synergizing plasmonic and photonic optical properties. 
2019 Science Fair poster rewarded with ISEF Finalist status and Naval Science Award.

ABSTRACT

Micro-/nano-structured surfaces in nature inspire many cutting-edge applications. Chameleon skin contains flexible micro-/nano-structures that can be geometrically tuned in response to environment to create different colors. Inspired by chameleons, this research focuses on fabricating flexible hemi-ellipsoidal micro-/nano-holes that be used in a long-term project for colorimetric strain sensing. Precise fabrication of 3D micro-/nano-structures, especially flexible structures, is difficult due to the small scale. To address this challenge, a two-photon lithography system was used to fabricate a master with micro-/nano-pillars. A software was written to control the laser parameters of the system to produce a variety of pillars sizes. Then, a flexible polymer was cast over the master to create flexible micro-/nano-holes. After fabrication, a 3D laser-scanning microscope was used to obtain the surface height maps of the samples. To efficiently extract structure dimension data from hundreds of surface height maps, a MATLAB software was developed. A model was created using JMP software to establish the relationship between the process parameters and the final structure dimensions. The study confirmed that higher laser powers and longer exposure times produce larger structures, as expected. Interesting interactions between the process parameters were also revealed. The physics of two-photon lithography was used to explain observed phenomena. This study enables colorimetric strain sensors with extremely high resolutions that could be used for cell development monitoring and other cutting-edge applications in many fields. Furthermore, the developed fabrication processes, MATLAB software, and JMP model can also be adapted for creating micro-/nano-structures for other applications.
2020 Science Fair poster rewarded with ISEF Finalist status.

ABSTRACT

Chameleon skin contains a lattice of guanine nanocrystals, the spacing of which can be tuned to create different colors in response to the environment. Inspired by chameleons, the goal of this research was to fabricate flexible, nanostructured nanoparticle-polymer composites and study the effects of strain on absorption spectra for sensing applications. This research synergistically combines two mechanisms for creating novel optical properties: chameleon-inspired nanopillar arrays and plasmonic nanoparticles. To precisely fabricate the nanopillar arrays, two-photon polymerization processes were optimized. Processes for mixing Ag nanocubes in uncured flexible polymer were then developed using a combination of centrifugal and magnetic mixing. A stretching apparatus was also designed to fit inside a spectrometer for spectra measurements of samples with various strains. After nanopillar fabrication, a scanning electron microscope was used to obtain pillar dimensions. The optical properties of the samples were measured at various strains using a UV-spectrometer. A model was created using JMP software to establish the relationship between the strain of the sample and the absorption spectra. As expected, strain resulted in a peak shift for samples with nanopillars, samples with nanoparticles, and their combinations. Interesting optical interaction between the nanostructures and nanoparticles was observed. This study has applications in colorimetric strain sensing and molecular sensing, both of which can be used for cell development monitoring and other cutting-edge applications in many fields.