Atomic Layer Deposition of Inorganic Thin Films on 3D Polymer Nanonetworks

Atomic layer deposition (ALD) is a unique tool for conformally depositing inorganic thin films with precisely controlled thickness at nanoscale. Recently, ALD has been used in the manufacture of inorganic thin films using a three-dimensional (3D) nanonetwork structure made of polymer as a template, which is pre-formed by advanced 3D nanofabrication techniques such as electrospinning, block-copolymer (BCP) lithography, direct laser writing (DLW), multibeam interference lithography (MBIL), and phase-mask interference lithography (PMIL). The key technical requirement of this polymer template-assisted ALD is to perform the deposition process at a lower temperature, preserving the nanostructure of the polymer template during the deposition process. This review focuses on the successful cases of conformal deposition of inorganic thin films on 3D polymer nanonetworks using thermal ALD or plasma-enhanced ALD at temperatures below 200 °C. Recent applications and prospects of nanostructured polymer–inorganic composites or hollow inorganic materials are also discussed.

Infrared Invisibility Cloak Based on Polyurethane-Tin Oxide Composite Microtubes

An invisibility cloak based on visible rays with a refractive index similar to that of air can effectively conceal people or objects from human eyes. However, even if an invisibility cloak based on visible rays is used, an infrared (IR) thermography camera can detect the heat (thermal radiation) emitted from different types of objects including living things. Therefore, both visible and IR rays should be shielded using an invisibility cloak produced by an appropriate technology. Herein, we developed a textile cloak that can almost completely conceal people or objects from IR vision. If a person or object is covered with an IR- and thermal-radiation-shielding textile woven with polyurethane (PU)-tin oxide (SnO₂) composite microtubes, serving as an IR invisibility cloak, IR and thermal radiation emitted from the person or object can be simultaneously blocked. Furthermore, the IR- and thermal-radiation-shielding characteristics could be improved further by filling the core of the PU-SnO₂ composite microtubes with heat-absorbing materials such as water and paraffin oil in place of air. In addition, the external surface of the IR- and thermal-radiation-shielding textile serving as an IR-reflecting cloak can be waterproofed to enable certain IR- and thermal-radiation-shielding functions under various environmental conditions.