Substrate Treatment Evaluation and Their Impact on Printing Results for Wearable Electronics

Abstract

This paper presents a comparative study on the treatment techniques for flexible polymeric substrates and their impact on the printing results. Substrate treatments are central to optimization of the printing processes and a strict set of requirements are needed to achieve uniform and acceptable printing results. Therefore, this research is highlighting the most significant treatment methods used for fine-tuning the surface properties of different polymeric substrates. Besides the two commonly used treatment techniques of oxygen plasma and ultraviolet ozone, a new method of using surface cleaning liquid is applied for rapid treatment of polymeric substrates. Comparative study is carried out on the basis of cleaning steps required for substrate preparation, processing, robustness as well as on the final printed results on the substrates. All the three treatment techniques with similar processing protocol are applied on a single type of polyimide (PI) substrate. To further validate the applicability and manufacture of practical devices, the liquid cleaning method is also applied on Polyethylene terephthalate substrates for making proof-of-concept wearable temperature sensor. From the study it is concluded that the liquid surface cleaning method is advantageous in terms of easy processing, robustness and producing uniform printing results on diverse polymeric substrates.

Inkjet Printing Optimization: Toward Realization of High‐Resolution Printed Electronics

“…Dielectric barrier discharge plasma was employed by Astanei et al to obtain hydrophilic surfaces of PET and polycarbonate (PC) films. [87] They proved that without the use of additional gases and the process was conducted at atmospheric [77] Copyright 2021, Frontiers; b) Water contact angle of PET, PI, and glass before (top) and after (bottom) HMDS treatment. Reproduced under the terms of Editors' Choice license.…”

“…The issues of bulging, disconnected, and non‐uniform Ag printing lines were practically solved when PI and PET films were chemically‐treated with the ESD cleaner. [ 77 ] However, the functionality of ESD is limited to hydrophobic and non‐porous polymer film only. ESD treatment on film with porous network with greater liquid absorption capacity, such as cellulose acetate film, resulted in significantly lower printing resolution and greater line width than the untreated ones ( Figure a).…”

“…Reproduced under the terms of the CC‐BY license. [ 77 ] Copyright 2021, Frontiers; b) Water contact angle of PET, PI, and glass before (top) and after (bottom) HMDS treatment. Reproduced under the terms of Editors’ Choice license.…”

“…Recommended values in the range of 62–78° are sufficient to guarantee optimal printing outputs. [ 77 ] Fine printing lines of graphene have been developed by treating PET, PI, and glass substrates with hexamethyldisilazane (HMDS) prior to printing (Figure 5b). [ 78 ] The methyl (─CH 3 ) groups in the HDMS molecules possibly bond to the functional groups of the polymer, rendering the CA of the substrates to increase after treatment.…”

“…Figure 5. a) Printing lines of Ag ink on untreated and ESD-treated polymer films. Reproduced under the terms of the CC-BY license [77]. Copyright 2021, Frontiers; b) Water contact angle of PET, PI, and glass before (top) and after (bottom) HMDS treatment.…”