Flexible electronic devices: the patent landscape

In the modern world, electronic devices are ubiquitous and, in many cases, have replaced traditional devices. With its unique flexibility, high performance and low-cost manufacturing, the technology has penetrated various industry sectors, including information technology, power and energy, medicine and defence. Notable applications include:

• flexible electronic displays;
• organic light-emitting diodes; 
• printed radio-frequency identification;
• thin-film solar panels; and
• electronic skin patches.

Patent landscape  
Patent filings for flexible electronic devices increased between 1997 and 2017 at an average rate of 15.7%; of these, 51.75% were filed between 2013 and 2017. The majority of research has been carried out in China, the United States, Japan and Korea, with China leading the way.

The patent literature reveals that such devices are mostly used for optoelectronics or thin-film transistors and that the majority of materials used are polymeric. Polymers provide mechanical, electrical and optical benefits and have been used for resists, encapsulation, insulators and intermediate dielectrics. Both hard and soft polymeric materials have been used in electronic devices as a base substrate. Materials used in this field include:

• polyimide; 
• polyester; 
• copper; and
• aluminium.

Flexible electronic devices can be made by using a semiconductor layer, insulating layer and conductive layer, either separately or combined. The most common techniques for producing these layers include chemical vapor deposition, physical vapor deposition and spray coating.

China is responsible for 31.11% of the total patents, followed by Japan (21.12%) and the United States (16.18%).

Lenovo and Samsung Electronics are the companies at the forefront of flexible electronics, focusing mainly on the use of plastic substrates for electronic devices, which is hard to achieve with conventional semiconductors and glass substrates.

Universities and research institutions which have also filed a significant number of patents in this domain include:

• the Industrial Technology Research Institute of Taiwan (ITRI);
• Huazhong University of Science and Technology;
• the Korea Advanced Institute of Science and Technology;
• Tsinghua University; and
• the South China University of Technology.

ITRI filed its first patent in 2003 and has filed 3.75% of the total patents. It is a non-profit R&D organisation founded in 1973 and cooperates with 23 major international companies, including IBM, Hewlett-Packard and Microsoft. 

The use of plastics (which are light, easy to operate and less expensive) as a base material has solved issues such as:

• low stability; 
• high cost; 
• low flexibility; and
• low power consumption.

Patent focus
Patent filings for flexible electronic products predominantly focus on:

• improving manufacturing methods;
• improving mechanical properties (eg, bending and stretching);
• reducing cost;
• improving the stability of adhesives; and
• improving material composition.

Most Chinese patents focus on circuit assembly, interconnecting circuits and methods for manufacturing flexible circuits. Materials such as nanoparticles are being used for producing more flexible bases (eg, opamine, trimethylol amino methane and ammonium persulfate).

The major assignees in this domain are:

• Lenovo;
• Samsung Electronics;
• Toshiba;
• Toyobo;
• Panasonic;
• Seiko Epson;
• Nissan Chemical industries; and
• Apple.

Comment
Based on the trend of patent filings, the R&D in the flexible electronic field is expected to increase at a compound annual growth rate of almost 11% between 2018 and 2023, and the production market is estimated to be worth $40.37 billion by 2023.

There appears to be more scope to resolve the technical challenges associated with this technology, such as low energy conversion efficiency, materials’ inability to bend and stretch, high costs, complex assembly processes and difficulty in repair and rework.

The following questions must also be addressed:

• Could this technology make electrical connections for applications, such as folding cell phones?
• Can the technology replace advanced multiple rigid boards or connectors in printed circuit boards, such as those used in cars, rockets and satellites?