Fabrication of Photonic Microbricks via Crack Engineering of Colloidal Crystals
Abstract
Evaporation‐induced self‐assembly of colloidal particles is one of the most versatile fabrication routes to obtain large‐area colloidal crystals; however, the formation of uncontrolled “drying cracks” due to gradual solvent evaporation represents a significant challenge of this process. While several methods are reported to minimize crack formation during evaporation‐induced colloidal assembly, here an approach is reported to take advantage of the crack formation as a patterning tool to fabricate microscopic photonic structures with controlled sizes and geometries. This is achieved through a mechanistic understanding of the fracture behavior of three different types of opal structures, namely, direct opals (colloidal crystals with no matrix material), compound opals (colloidal crystals with matrix material), and inverse opals (matrix material templated by a sacrificial colloidal crystal). This work explains why, while direct and inverse opals tend to fracture along the expected {111} planes, the compound opals exhibit a different cracking behavior along the nonclose‐packed {110} planes, which is facilitated by the formation of cleavage‐like fracture surfaces. The discovered principles are utilized to fabricate photonic microbricks by programming the crack initiation at specific locations and by guiding propagation along predefined orientations during the self‐assembly process, resulting in photonic microbricks with controlled sizes and geometries.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Dec 13, 2019
- Source ID
- 10.1002/adfm.201908242
Entities
People
- Cathy Zhang
- Chao Gao
- Haizhao Yang
- Joanna Aizenberg
- Katherine R Phillips
- Lei Liu
- Ling Li
- Soeren Brandt
- Theresa Kay
- Ting Yang
- Yaning Li
Organizations
- Army Research Office
- Division of Materials Research
- Harvard University
- Massachusetts Institute of Technology
- Northeastern University
- Purdue University
- University of New Hampshire
- Virginia Tech