Robust, Conformal ZnO Coatings on Fabrics via Atmospheric‐Pressure Spatial Atomic Layer Deposition with In‐Situ Thickness Control**

Abstract Zinc oxide (ZnO) is a promising material for functionalization of textiles. It can add a range of functionalities, including UV protection, antimicrobial activity, flame retardancy, hydrophobicity and electrical conductivity. Commercialization of ZnO – coated textiles is still limited due to the cost and challenges related to their manufacture. Moreover, making robust coatings on textiles and measuring their thickness is also challenging. In this work, atmospheric‐pressure spatial atomic layer deposition (AP‐SALD) systems are utilized for the first time to coat synthetic spun‐bond polypropylene (PP) and natural cotton fabrics with ZnO. The coatings are found to be conformal and uniform, forming complete shells around the fabric fibers. The growth rate is measured to be ∼0.24 nm/cycle using an in‐situ reflectance setup and Virtual Interface (VI) model, which enable precise control of the coating thickness. The coatings are shown to provide UV‐protection and render cotton fabric hydrophobic. No damage is observed after washing, linear abrasion, adhesion, twisting and bending tests, indicating that the coatings are robust. Aerosol‐penetration tests indicate the coatings do not impact the filtering efficiency of fabrics used in N95 respirators. The results are encouraging for industrialization of the AP‐SALD technique for functional textiles.