Research

INNO-KOM 49MF200078

Abstract
In order to integrate electronic components into clothing, conductive thread materials must be flexible and resilient. Conventional protective coatings often insulate and hinder electrical contacting. Nanoscale SiOX coatings do not insulate and can be chemically functionalized. They are suitable for improving wash re-sistance, electrical skin contact and even the construction of chemically sensitive electrodes based on metal-lized yarns. The result of the ElChemNano project is a technology for the continuous, electrochemical deposi-tion of SiOX layers in order to gently functionalize metallized yarns. It is possible to continuously deposit reactive SiOX adhesion promoter layers. The maximum tensile strength and elongation remain virtually un-changed.

Problem
Chemically reactive SiOx layers enable metallized yarns to be functionalized. Cathodically induced polymerization of silicic acid offers the possibility of electrochemically depositing SiOx nanolayers selectively on metallized yarns at room temperature. In the preliminary project katinPol (INNO-KOM-Ost VF150029), this type of deposition on filamentous substrates was investigated on a laboratory scale. The main objective of ElChemNano is to transfer the electrochemical deposition developed in the laboratory into a continuous process in order to produce filament materials that can be processed using textile technology.

Solution
In order to develop a technology for the continuous electrochemical deposition of SiOx layers, the results from the laboratory scale are being transferred to a continuous thread galvanizing plant (Figure 1). To this end, the plant technology is being adapted to the requirements of the new process. The challenge lies in transferring the deposition parameters to a larger scale and the changed conditions on the moving thread. At the same time, the production and maintenance of the electrolyte required for deposition is being investigated on a larger scale. In addition, suitable methods for pre-treating the metallized yarns must be developed to prevent contamination of the substrates from interfering with the electrochemical deposition. Furthermore, the resulting SiOx layers and their effects on the properties of the metallized yarns after electrochemical coating must be investigated.

Fig. 1: Schematic representation (left) and photo of an electroplating module (right) for continuous electrochemical deposition on conductive filament materials

Results and Applications

A technology is available for the continuous electrochemical deposition of SiOx layers at thread speeds of up to 12 m/min. The starting material is a silver-plated polyamide yarn with a fineness of 117f17x2. After galvanic reinforcement of the silver layer and wet chemical pretreatment, it is fed into the thread electroplating plant. SiOx layers can be continuously deposited with a silicon concentration of at least 0.2%, but they are not yet as uniform as those produced in the CVD process. This results in abrasion resistance that is not yet satisfactory in the weaving process. However, the bonding of selected functional layers has been successfully demonstrated (Figure 2). Chemical functionalization can potentially even be integrated into the continuous process. The electrical resistance of the metallized yarns is not significantly altered, and the maximum tensile strength and elongation are reduced by less than 5% compared to the starting material. The continuous process is ensured by increasing the service life and using the electrolyte in batches. Based on the basic technology developed in this project for the continuous electrochemical deposition of SiOx bonding agent layers, subsequent work must optimize the activation and deposition parameters in order to obtain significantly more uniform layers.

Fig. 2: Proof of the chemical functionality of the electrochemically applied SiOx layer by staining with methylene blue in a continuous process

We would like to thank the Federal Ministry for Economic Affairs and Climate Protection for its financial support of the research project “ElChemNano” 49MF200078.