Cracking-assisted fabrication of nanoscale patterns for micro/nanotechnological applications

Abstract

Cracks are frequently observed in daily life, but they are rarely welcome and are considered as a material failure mode. Interestingly, cracks cause critical problems in various micro/nanofabrication processes such as colloidal assembly, thin film deposition, and even standard photolithography because they are hard to avoid or control. However, increasing attention has been given recently to control and use cracks as a facile, low-cost strategy for producing highly ordered nanopatterns. Specifically, cracking is the breakage of molecular bonds and occurs simultaneously over a large area, enabling fabrication of nanoscale patterns at both high resolution and high throughput, which are difficult to obtain simultaneously using conventional nanofabrication techniques. In this review, we discuss various cracking-assisted nanofabrication techniques, referred to as crack lithography, and summarize the fabrication principles, procedures, and characteristics of the crack patterns such as their position, direction, and dimensions. First, we categorize crack lithography techniques into three technical development levels according to the directional freedom of the crack patterns: randomly oriented, unidirectional, or multidirectional. Then, we describe a wide range of novel practical devices fabricated by crack lithography, including bioassay platforms, nanofluidic devices, nanowire sensors, and even biomimetic mechanosensors.

Fabrication of Photonic Microbricks via Crack Engineering of Colloidal Crystals

“…While cracks are generally considered detrimental to a device's performance, rational engineering of crack nucleation and growth has been recently exploited as a novel fabrication strategy to produce nano-and microscopic patterns and structures. [39][40][41] Intentionally designed cracks in 'traditional' crystalline and polymeric thin films have found some unique applications in cellular patterning, [42] integrated micro/nanofluidic devices, [39,43] nanowire-integrated gas sensing, [44] mechanosensing, [45] transparent electrodes, [46] and electrochromic structures. [47] Currently, very few studies exploit the possibility of engineering the crack formation in colloidal crystals.…”

Drying colloidal systems: Laboratory models for a wide range of applications

“…30. Variations in the substrate can be engineered to nucleate, halt, bend or redirect cracks in a layer above them [155][156][157]. Art can be made by creative control over this, as in the works of Andy Goldsworthy [158].…”

Scaling Law for Cracking in Shrinkable Granular Packings

“…Cracking is often undesirable, damaging structures built on clay-rich soil, causing waste leakage from subsurface clay barriers [2], altering the texture of foods [3], disrupting biological tissues [4], and limiting the performance of coatings [5]. In other cases, cracking is desirable, but must be controlled; emerging examples include micro/nano-patterning [6] and transport in fuel cells [7]. However, despite the ubiquity and practical importance of this phenomenon, accurate prediction of cracking remains elusive.…”