Innovative manufacturing processes herald a new era for flexible electronics

New and repurposed fabrication techniques for flexible electronic devices are proliferating rapidly. Some may wonder if they are better than traditional methods and at what point they’ll be commercialized. Will they influence electronics design engineers’ future creations?

Flexibility is catching on. Experts forecast the flexible electronics market value will reach $63.12 million by 2030, achieving a compound annual growth rate of 10.3%. As its earning potential increases, more private companies and research groups turn their attention to novel design approaches.

Flexible electronics is a rapidly developing area. Source: Institute of Advanced Materials

As power densification and miniaturization become more prominent, effective thermal management grows increasingly critical—especially for implantable and on-skin devices. So, films with high in-plane thermal conductivity are emerging as an alternative to traditional thermal adhesives, greases, and pads.

While polymer composites with high isotropic thermal conductivity (k) are common thermal interface materials, their high cost, poor mechanics, and unsuitable electrical properties leave much to be desired.

Strides have been made to develop pure polymer film with ultrahigh in-plane k. Electronics design engineers use stretching or shearing to enhance molecule chain alignment, producing thin, and flexible sheets with desirable mechanical properties.

Here, it’s important to note that the fabrication process for pure polymer films is complex and uses toxic solvents, driving costs, and impeding large-scale production. A polyimide and silicone composite may be the better candidate for commercialization, as silicone offers high elasticity and provides better performance in high temperatures.

Novel manufacturing techniques for flexible electronics

Thermal management is not the only avenue for research. Electronics engineers and scientists are also evaluating novel techniques for transfer printing, wiring, and additive manufacturing.

Dry transfer printing

The high temperatures at which quality electronic materials are processed effectively remove flexible or stretchable substrates from the equation, forcing manufacturers to utilize transfer printing. And most novel alternatives are too expensive or time-consuming to be suitable for commercial production.

A research team has developed a dry transfer printing process, enabling transferring thin metal and oxide films to flexible substrates without risk of damage. They adjusted the sputtering parameters to control the amount of stress, eliminating the need for post-processing. As a result, the transfer times were shortened. This method works with microscale or large patterns.

Bubble printing

As electronics design engineers know, traditional wiring is too rigid for flexible devices. Liquid metals are a promising alternative, but the oxide layer’s electrical resistance poses a problem. Excessive wiring size and patterning restrictions are also issues.

One research group overcame these limitations by repurposing bubble printing. It’s not a novel technique but has only been used on solid particles. They applied it to liquid metal colloidal particles—specifically a eutectic gallium-indium alloy—to enable high-precision patterning.

The heat from a femtosecond laser beam creates microbubbles that guide the colloidal particles into precise lines on a flexible substrate. The result is wiring lines with a minimum width of 3.4 micrometers that maintain stable conductivity even when bent.

4D printing

Four-dimensional (4D) printing is an emerging method that describes how a printed structure’s shape, property or function changes in response to external stimuli like heat, light, water or pH. While this additive manufacturing technique has existed for years, it has largely been restricted to academics.

4D-printed circuits could revolutionize flexible electronics manufacturing by improving soft robotics, medical implants, and wearables. One proof-of-concept sensor converted pressure into electric energy despite having no piezoelectric parts. These self-powered, responsive, flexible electronic devices could lead to innovative design approaches.

Impact of innovative manufacturing techniques

Newly developed manufacturing techniques and materials will have far-reaching implications for the design of flexible electronics. So, industry professionals should pay close attention as early adoption could provide a competitive advantage.

Ellie Gabel is a freelance writer as well as an associate editor at Revolutionized.

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