Achieving order with two-photon lithography : colloidal self-assembly and direct laser writing
Abstract/Contents
- Abstract
- Structural or spatial order at the nanometer/micron regime is an avenue to improve material properties. The field of photonics and metamaterials have shown that size-effects at these regimes, in combination with purposefully designed architected structures, can enhance mechanical and optical performance. A common approach to achieve these types of ordered structures is through colloidal self-assembly or direct laser writing of 3D structures. In this work, I propose using direct laser writing to fabricate colloidal particles and to fabricate complex 3D structures that have enhanced mechanical properties. In the first part of my work, I focus on colloidal self-assembly as a method to achieve order. Due to the limited chemistries and shapes of colloids available to self-assemble, a large majority of self-assembled structures remain elusive. I propose using two-photon lithography to fabricate micron-sized particles and experimentally study the effect of shape (both concave and convex) on the final self-assembled structure. This method allows for highly monodisperse fabrication of colloidal particles which can then be imaged using optical techniques due to their micron size. I fabricate colloidal conical shapes that self-assemble under entropic conditions (depletants) and tune the degree of assembly by changing the effective driving force through size. I then use a custom machine learning framework to identify these assembled structures (columnar grains) and recover self-assembly trends in which larger particles show a higher degree of self-assembly. Building upon this work, convex particles, specifically the Archimedean truncated tetrahedron, are also fabricated using the same framework and studied under another entropic condition (hard-particle interaction). These particles assemble in a six-fold symmetry upon interaction with an interface and transition to a three-fold symmetry upon application of a potential field. Analytical and computational results show that the six-fold symmetry state is a quasi-stable state and upon additional energy input, a transition occurs to achieve the lower energy state. In the second part of my work, I use two-photon lithography in conjunction with nanoclusters to enhance the direct laser writing process and improve the mechanical properties. I fabricate lattices with micron sized features and test them mechanically. The resulting nanocomposite lattices shows high stiffness and best-of-class energy absorbance by suppressing layer by layer collapse that is commonly seen with these types of structures.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2023; ©2023 |
| Publication date | 2023; 2023 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Doan, David |
|---|---|
| Degree supervisor | Gu, Wendy, (Professor of mechanical engineering) |
| Thesis advisor | Gu, Wendy, (Professor of mechanical engineering) |
| Thesis advisor | Cai, Wei, 1977- |
| Thesis advisor | Tang, Sindy (Sindy K.Y.) |
| Degree committee member | Cai, Wei, 1977- |
| Degree committee member | Tang, Sindy (Sindy K.Y.) |
| Associated with | Stanford University, School of Engineering |
| Associated with | Stanford University, Department of Mechanical Engineering |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | David Doan. |
|---|---|
| Note | Submitted to the Department of Mechanical Engineering. |
| Thesis | Thesis Ph.D. Stanford University 2023. |
| Location | https://purl.stanford.edu/fx893qp0585 |
Access conditions
- Copyright
- © 2023 by David Doan
- License
- This work is licensed under a Creative Commons Attribution 3.0 Unported license (CC BY).
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