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Technology that once seemed restricted to the realms of science fiction is rapidly becoming a reality. Recent years have seen industry-leading companies releasing products that incorporate flexible electronics that not only bend and fold to expand capabilities but are also ultra-thin.
The idea of flexible electronics is not new. Back in the 1960s, flexible electronics were first used to create extraterrestrial satellites. However, their development was stalled until recently. An array of products are now on the market, including smart credit cards that incorporate silicon-based flexible microchips.
Tech news over the past couple of years has also featured the launch of products such as televisions so thin and flexible that they can roll up like a projector screen. Apple recently filed a patent that suggests it will be investigating the possibility of developing a foldable smartphone.
What are Flexible Electronics?
These kinds of futurist technologies are made possible by flexible electronics. Any flexible electronic device is constructed of four components:
Each of these components must be flexible to an equal degree and must not suffer from a loss or reduction in function to achieve this flexibility.
The Focus on Silicon
The focus of developing electronics such as modern laptops has previously been on silicon technology due to its semiconducting capabilities.
The material is an excellent conductor as it allows "charge carriers” to freely move through its silicon crystals. However, its use in creating flexible electronics is limited due to the rigidity of the material. For this reason, scientists have turned the spotlight onto plastics.
Deepening our Knowledge of Conducting Polymers
Flexible electronics involves fixing electronic circuits onto flexible substrates. Plastic has become the primary material used as the substrate in these developments. Most often, the plastic is made from either PEEK, polyimide, or transparent conductive polyester film. Essentially, scientists are designing plastics with the ability to conduct electricity.
While plastics have been used in a myriad of industries since the 1950s, they are only just emerging in the field of commercial electronics. Conducting plastics suffer the setback of being less efficient at conducting an electrical charge, which has allowed silicon to take the top spot in developing electronic devices.
However, plastic is flexible where silicon is not, and it is also cheaper, easier to work with, lighter, and can be transparent. This list of advantages has forced scientists to reconsider the potential of plastics in electronics.
Testing the conductivity of a material is essential for ensuring the success of a new electrical product. Conventional methods involve soldering contacts to a material to test how well it conducts electricity. However, it is often a challenge to make good contacts with polymers.
This has been a major hurdle to the development of electrical polymers. A team at the National Institute of Standards and Technology (NIST) recently set out to address this problem by innovating a reliable method of testing the directional conductivity of polymers that do not rely on contact and instead utilize two types of light.
The technique involves creating electrons and holes in the sample material by introducing visible light in ultrashort pulses. Next, polarized terahertz (THz) radiation, light that is outside of the visible light range, toward the microwave range, is shone onto the sample.
The results of the study were published in March in the Journal of Physical Chemistry C. They demonstrate the effectiveness of the technique in helping scientists to understand the nature of polymers in an unprecedented way. The experiment described in the paper sees the researchers use the THz method on two simple conductive polymers, PCDTPT and P3HT, in the form of nanofilms.
Their experiment demonstrated that the PCDTPT solution was not only conductive, to their surprise, but it was also equally conductive as a liquid and solid. P3HT, on the other hand, was shown not to be conductive. Previous behavior had never been witnessed before in a polymer. In addition, the team was able to uncover the nature of the conductivity, using the light method to determine that the conductivity was occurring within and along strands of the polymer, not between the strands, as was originally thought.
The THz method is opening up the use of polymers in flexible electronics because scientists can now effectively, simply, and reliably measure the conductivity of their devices.
Future Directions for Flexible Polymers
The market for flexible electronics is widening, with a growing demand for flexible displays and smaller devices. With this new method of testing polymer conductivity, scientists are equipped to develop new, flexible electronic devices for the future.
References and Further Reading
A Peek Inside the World of Flexible Electronics. MatMatch. Rishabh A. Kothari. https://matmatch.com/blog/flexible-electronics-world/
Apple patent explores crease-free folding phone. BBC News. https://www.bbc.co.uk/news/technology-51385134
Flexible hybrid electronics: The future of flexible printed circuit boards. Cambridge Network. https://www.cambridgenetwork.co.uk/news/flexible-hybrid-electronics-future-flexible-printed-circuit-boards
LG’s new 77-inch OLED wallpaper TV is now available for the price of a new car. The Verge. Chaim Gartenberg. https://www.theverge.com/2017/6/28/15887040/lg-w7-20000-77-inch-oled-wallpaper-tv-4k-hdr-available
LG's rollable OLED TV is incredible, and it's actually going on sale in 2019. CNET. David Katzmaier. https://www.cnet.com/news/lgs-rollable-oled-tv-is-incredible-and-its-actually-going-on-sale-in-2019-ces/
The Future is Bright for Flexible Electronics. Money Inc. Bill Vix. https://moneyinc.com/flexible-electronics/
Roll-up TVs and bendable smart phones: The future of flexible electronic materials. phys.org. Jennifer Lauren Lee. https://phys.org/news/2020-03-roll-up-tvs-bendable-smart-future.html