Plasma-based surface treatment is a mature technology in many respects, but it has not been fully exploited in medical textile applications, according to Dirk Hegemann, group manager of the plasma-modified surfaces division at Empa, Swiss Materials Science & Technology. Researchers at the center intend to remedy that. Applying the technology to yarn that is then woven into textiles may enhance a product's antimicrobial, antistatic, hydrophobic, and hydrophilic properties, along with its biocompatibility and lubricity. The technology also has potential for enhancing long-term patient-monitoring applications.

"Plasma coating has not yet been commercialized for the continuous coating of yarn," says Hegemann. Empa is currently developing a technology to achieve this. The use of silver coatings to obtain antibacterial and electrically conductive properties are applications that have sparked the interest of researchers.

The coatings are applied one atomic layer at a time. This enables researchers to precisely control the amount of silver that is deposited on the yarn and to fine-tune the adhesive properties. By modifying the fiber and yarn surfaces at the nano level, Hegemann adds, textile properties such as flexibility, mechanical strength, and touch are retained.

Plasma is a reactive, ionized gas that is excited by electric fields. Regardless of plasma conditions such as gas composition, energy input, and pressure, a high level of process control can be achieved. And because this is a dry technology, it could replace wet chemical process operations in the textile industry that are typically associated with high levels of chemical and water consumption. It also makes selective adjustment of surface wettability possible.

Plasma-coated yarns woven into textiles provide antimicrobial and antistatic properties that can prevent blood or secretions from passing through the material, for example. These properties enable the textile to kill germs and prevent electric charging in applications when necessary. According to Hegemann, hydrophobic, hydrophilic, biocompatible, and friction-reducing properties are also achievable.

The silver coating also imparts conductivity to the yarn, enabling its use in textile-based electrodes. The material could be used to manufacture clothing that doubles as an ECG device for long-term patient monitoring. Textile electrodes also may be used in electrostimulation products. In fact, says Hegemann, "multifunctional fibers can lead to a host of new products."

Furthermore, the technology's suitability for neuroprosthetics and regeneration is being investigated in a collaborative project by the Institute for Automation at the Swiss Federal Institute of Technology (ETH) in Zürich and Compex Médical S.A. (Ecublens, Switzerland), which manufactures muscle stimulation devices.

Empa, Swiss Materials Science & Technology, St. Gallen, Switzerland
www.empa.ch

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