Connecting the printed electronics and wearables communities

Wearable devices will benefit from advances in printed electronics technologies

By Alan Hodgson, Chair IEC TC 119

Printed electronics as a manufacturing method has become established in a number of areas across the electrotechnical world. The connections that are made are emerging as particularly significant in the new generation of wearable electronic devices. Although some wearable applications can be realized using wholly conventional rigid electronics, many will require some element of flexibility. Standardization work by a number of IEC Technical Committees (TCs) and subcommittees (SCs) is central to this development.

motion-tracking elbow and wrist sensors Motion tracking with elbow and wrist sensors (Photo: Fraunhofer ISIT)

Printed electronics anywhere

Printing is becoming a fabrication technique applicable to the manufacturing of devices on a variety of scales. The technology has moved on from printing ink in devices such as office printers [1] to become a deposition tool for electrotechnical component manufacture. This is because printing techniques allow industry to produce devices and structures over a wide area with printing processes that are also open to roll-to-roll processing (see Printing electronics anywhere in e-tech issue 06/2016).

A current example of this capability is provided in the production of photovoltaic (PV) devices. Printed electronics is one of the supporting technologies for the manufacture of these devices (see Supporting technologies for photovoltaics in e-tech issue 08/2016). In this application, it is particularly suited to the screen printing of the conductive backplane but this is now expanding into other functional layers.

This expansion is mirrored in other electrotechnical applications, most notably in display and lighting. The conductive backplane capability in this case finds application in the fabrication of touch screen edge electrodes, bringing to printed electronics a connection with work from IEC TC 110: Electronic display devices. As techniques advance, these printing techniques are developing into further manufacturing opportunities, from the deposition of barrier layers and printing of coloured bezels to 3D printing of electromagnetic screening. The work involves Standards developed by IEC TC 106: Methods for the assessment of electric, magnetic and electromagnetic fields associated with human exposure.

IEC TC 119: Printed electronics, is beginning to work on these areas of connected-to-device production, starting with the recent publication of IEC 62899-502-1:2017, Printed electronics – Part 502-1: Quality assessment – Organic light emitting diode (OLED) elements – Mechanical stress testing of OLED elements formed on flexible substrates. To follow this, IEC 62899-501-1 will look at failure modes and the mechanical testing of flexible and/or bendable primary or secondary cells. 

Connecting with other communities

Flexible electronics is of substantial interest to some industry bodies and forms a strong connection with the work within the IEC. For example, at the 2016 Frankfurt General Meeting, the Organic Electronics Association (OE-A) held a European gathering, concurrent with IEC TC 119, which enabled members of both communities to connect and share expertise.

The OE-A and IEC TC 119 have common interests in the industrialization of printed electronics but the synergy is wider than this. The OE-A has proved to be an active supporter of International Standards for flexible electronics and at recent events it has given space in its agenda for presentations on the relevant work within the IEC community, as well as meeting space for IEC working groups at its conferences. This alliance is of particular importance as we move these technologies onto further common ground such as the internet of things (IoT), printed sensors and flexible, hybrid and wearable electronics.

The IoT is a good example of a cluster of technologies that is attracting widespread industrial interest. It also represents a substantial opportunity for printed electronics technologies. Wide area sensor arrays in particular look likely to provide the external input interface to IoT systems. In this respect the link with ISO/IEC JTC 1/SC 41: Internet of things and related technologies, is likely to become important. Working together we can look to standardize some of the new form factors for future IoT electronics solutions. 

Flexible, bendable, rollable, stretchable

Printing and other thin film deposition techniques bring forward the possibility of new form factors for electronics, starting with flexible substrates. This has now been standardized as IEC 62899-201:2016,  Printed electronics – Part 201: Materials – Substrates. This represents only a part of the story towards the industrialization of flexible electronic devices and the concept of hybrid electronics must be introduced here.

In this context, hybrid means the combination of printed and “conventional” (silicon-based) electronics. Hybrid is probably the medium-term route to flexible electronics, allowing linked communities to combine the capabilities of mature silicon-based electronics with flexible substrates. Here there is synergy between the work of IEC TC 119 and of IEC TC 91: Electronics assembly technology, particularly as both groups explore hybrid (rigid plus flexible) electrotechnical assemblies. The 2016 Frankfurt General Meeting was a great opportunity to meet together to guide our work into this common ground.

Other IEC TCs are working to support flexible electronics too. For example, IEC TC 47: Semiconductor devices, has recently published IEC 62951-1:2017, Semiconductor devices – Flexible and stretchable semiconductor devices – Part 1: Bending test method for conductive thin films on flexible substrates, and is working on other documents in this series. And as displays are already adopting flexible, bendable and rollable formats, IEC TC 110 has published the IEC 62715 series of standards on flexible display devices.

As we move forward into a wider suite of applications, other parameters will require standardization. As an example, the barrier layers described in an e-tech article are important for photovoltaic, display and lighting technologies. As these transition into flexible substrates, the test methods for these flexible barriers will also become important and are currently being worked on by IEC TC 47 as IEC 62951-7.

The progression into stretchable electronics brings with it new opportunities but also new challenges. Standardization work has commenced in this area, notably with evaluation methods for stretchable substrates as IEC 62899-201-2. This is an important area for the IEC community as it presents new opportunities in wearable electronic devices. 

Bringing forward the wearables agenda within the IEC

The 2016 Frankfurt General Meeting was notable in a number of ways in bringing forward the wearables agenda within the IEC. In the IEC TC 119 meetings, progress was made on Standards documents to support printed wearable electronics. However, the most significant advances came at IEC Standardization Management Board (SMB) level with the resolution to create a new TC for wearable electronic devices that became IEC TC 124: Wearable electronic devices and technologies. This technical area is seen to be gaining in importance, especially in the fields of wellness, health and medicine.

The wearable devices sphere (see The wearable future in e-tech issue 01/2016) has been noted as important for the future and is another example where connecting communities will be essential. This is an area where work from many IEC TCs overlaps and as a result, open liaison will be essential to ensure this work progresses. Textile-based electronics is an area set to expand. As an integral part of future functionally-enabled clothing, it is likely to represent an early application area of wearable devices and will thus be a prime area for standardization.

Although IEC TC 124 has yet to meet, standardization work has already commenced within the IEC. IEC TR 62899-250:2016 , Printed electronics – Part 250: Material technologies required in printed electronics for wearable smart devices, is a contribution that sets the scene for the substrate area of IEC TC 124. 

Looking forward

The relevant communities are beginning to coalesce around IEC TC 124. In addition to the list of IEC TCs, the expertise of the Advisory Committee on information security and data privacy (ACSEC), and of the IEC Systems Committee on active assisted living, IEC SyC AAL, are likely to be of importance. This looks certain to be a growth area for the IEC.

Printed electronics has the potential to be an enabling technology for a number of applications areas.

IEC TC 119 continues to explore these opportunities through its working groups and plenary meetings.

[1] International Standards for office printers are developed by ISO/IEC JTC 1/SC 28: Office equipment, a subcommittee (SC) of the joint technical committee formed by the IEC and the International Organization for Standardization (ISO).

Gallery
motion-tracking elbow and wrist sensors Motion tracking with elbow and wrist sensors (Photo: Fraunhofer ISIT)
infographics motion-tracking elbow and wrist sensors How the motion tracking with elbow and wrist sensors works (Image: Fraunhofer ISIT)
3D-printed dome Printed conductors for EM shielding (Photo: Optomec)