CeNTI: Printed and flexible electronics in sm...
CeNTI

Printed and flexible electronics in smart textiles

Since 2006, the research institute CeNTI – Centre for Nanotechnology and Smart Materials has been involved in a wide number of research and innovation projects in the field of smart textiles, supporting several industrial partners from different application sectors in the development of smart textile-based products with high added value.

The field of smart textiles is evolving and emerging as a reality, from wearables and car interior surfaces to home textiles, with different applications reaching the market. Smart textiles stand out as products of high technological value and impact in the market, justifying the continuous growth and differentiation of the textile industry in the development and innovation of such products.
The activity of CeNTI in the development of technologies for the textile sector is set within this context. Through the application of printed electronics, functional fibers and yarns, smart systems and customized integration processes, it is possible to achieve disruptive textile-based products with added functionalities. This ranges from wearable textile sensors to flexible actuation and interface systems such as interactive surfaces, haptic feedback, light output and heating systems.

Smart textiles for the automotive industry
Automotive interior textiles represent almost 50% of the interior area in contact with the user, presenting a very good opportunity for the incorporation of seamless and smart functionalities to enhance driver and passenger comfort, safety, and interactivity. In the past years, CeNTI has been collaborating with several partners from the automotive sector, providing new functionalities through the application of flexible devices produced either by the application of printed electronics, or through the application of fiber/yarn-based devices (e.g. sensors, actuators) incorporated by advanced textile processes.
The Future Door Panel project is one of the examples of the institute’s involvement in this area; the project intends to develop a distinctive, innovative and differentiating door panel, creating an intuitive human-machine interface oriented to the end user. Different objectives are considered in this project led by Simoldes Plastics, Oliveira de Azeméis/Portugal, namely achieving door panel weight reduction, new acoustic solutions, or haptic and capacitive printed sensors fully integrated on door panel components. “In the field of smart textiles, this project intends to obtain textile structures with embedded printed electroluminescent devices, integrated by a press covering process into a polymeric piece, providing visual comfort to the user,” explains researcher Daniela Campanhã.

Leading demonstrator with electroluminescent printed device (FDPanel project) (Source: CeNTI)
Leading demonstrator with electroluminescent printed device (FDPanel project) (Source: CeNTI)
Smart textiles for healthcare applications
The demand for smart textile-based solutions for the healthcare sector has been growing over the past years, demonstrating the strong benefits that smart textile devices can have in patient treatments, disease diagnosis and user wellbeing.
This is also a sector targeted by CeNTI, in the mobilizing project Smart-Health-4-All. Led by the Siemens Healthineers from Siemens Healthcare GmbH, Erlangen/Germany, Smart-Health-4-All aims to stimulate an ecosystem dedicated to research and development, production, marketing and dissemination of medical technologies in Portugal, based on information, communication, and electronic technologies (IECT), and on Future and Emerging Technologies (FET). The project crosses different areas of knowledge, such as health sciences and engineering, as well as high-tech sectors (e.g. TICE, nanotechnologies) with other traditional ones, including textiles as one of the main sectors being addressed. “Within this project, CeNTI is exploring new solutions for different areas within the health sector together with different actors from the textile industry – namely new wearable solutions (e.g. textile sleeves) for muscular rehabilitation and a smart pillow for sleep quality monitoring,” explains researcher Kevin Rodrigues.
In parallel, the institute is exploring other technologies with high added value for the health sector, namely printed/flexible textile electrodes for electromyography (EMG) and electrostimulation (TENS), allowing not only the monitoring of muscular response (EMG) but also muscular recovery through TENS. The Wear2Heal project, led by Tintex Textiles SA, Campos, V.N. de Cerveira/Portugal, is one example for these technologies, which includes the development of smart sports clothing for muscle therapy with the integration of electronic textile solutions onto the fabric of the garment. “Wear2Heal is developing a solution that will enable the integration of textile actuators directly onto sports garments, which in turn will provide active muscle recovery enhancement,” explains researcher Marta Midão.

Printed heating system applied on textile surfaces (Wear2Heal project) (Source: CeNTI)
Printed heating system applied on textile surfaces (Wear2Heal project) (Source: CeNTI)
Printed electronics for textile-based applications
The integration of printed electronics presents a very good solution to add functionality to traditional textile structures, from woven to knitted fabrics, without compromising their intrinsic properties, i.e. lightness, adaptability, and conformability. Throughout the years, CeNTI has increased its expertise in this field through the application and development of several different functional inks, ranging from conductive-based inks to dielectric, phosphorescent, piezoelectric, or thermoelectric based inks, allowing the development of different printed devices capable of adding disruptive functionalities to textiles. Within these functionalities, it is possible to highlight smart textile solutions with embedded sensors, actuators, energy harvesting, haptic feedback, and light and thermal outputs. CeNTI’s mission in the field of printed electronics is also to transfer this technological expertise to different industrial sectors, where for example a screen-printed temperature sensor can be used not only to monitor the skin temperature of the user, when applied in a smart textile context, but also be applied for the monitoring of perishable products, connected to the packaging industry. The 48H Frozen project is an example of this application: it involves the development of temperature sensors printed by the screen-printing technique that can be incorporated by injection molding into plastic packages, produced by Plásticos Futura, Lda., Leiria/Portugal. The printed sensor features an interdigitated design with high sensitivity and fast response and is capable of monitoring packaging temperature. “The sensor is printed with conductive ink and has a very thin track thickness improving its sensitivity,” confirms researcher Vanessa Miranda.

Fiber and yarn-based flexible devices
CeNTI’s role within the smart textiles field is not only limited to the application of printed electronics. The technology transfer center is also working on the development of non-conventional fibers (by tri-component extrusion processes) with multifunctionality, ranging from fiber-based sensors, actuators, impact absorption fibers and even textile energy harvesters. This know-how combined with the application of smart materials, namely functional conductive yarns (e.g.: copper, stainless steel) allows the development of completely textile-based solutions with added functionalities. The technological transfer of these fiber-based solutions to the textile industry is one of the main goals, which implies a profound study from an early stage of the materials and processes to be used in the devices to ensure that they comply with the high standards of the textile sector. The Portuguese project iHEATEX, led by JF Almeida, was an example of this application, exploring new tri-dimensional terry structures and architectures with multifunctionality and intelligent hybridisation, for application in household and hotel textiles. The project resulted in the development of textile products (e.g.: a bath robe) with integrated intelligent heating systems, through the integration of functional yarns during the weaving process, resulting in textile structures with improved moisture management and heating capabilities.  

Flexible and intelligent heating system embedded in a bath robe (iHEATEX project) (Source: CeNTI)
Flexible and intelligent heating system embedded in a bath robe (iHEATEX project) (Source: CeNTI)
The projects mentioned in this article are co-financed by Portugal 2020, under Operational Programme for Competitiveness and Internationalization (COMPETE2020) through the European Regional Development Fund (ERDF).
About CeNTI
CeNTI – Centre for Nanotechnology and Smart Materials, Vila Nova de Famalicão/Portugal, is a private non-profit research and development (R&D) institute which provides applied R&D for industrial endogenization of new disruptive technologies, product engineering and upscale for companies using a B2B approach. CeNTI’s mission is to drive the development of material solutions for product innovation across multi-TRL stages, specifically in areas encompassing nanomaterials, functional materials, smart materials and systems, design, and engineering, targeting a wide range of applications in industrial sectors such as automotive/aeronautics, architecture/construction, and sport/personal protection/health and well-being.
As a research and technology transfer center, in its portfolio of innovation and R&D activities CeNTI presents several projects that demonstrate its commitment and mission to support and promote the industrial and business technological infrastructures, with the aim of developing new products with high added value and/or incorporate new technologies into traditional products and markets.
This article was originally published in OPE Journal, No. 39, June 2022

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