Researchers from the Daegu Gyeongbuk Institute of Science and technology have recently developed a transfer method for printing flexible electronic circuits without complex machinery. What challenges do flexible electronics face, what did the researchers demonstrate, and how will it help develop flexible electronics in the future?

What challenges does flexible electronics face?

Flexible electronics are key to the creation of electronic systems used in mechanically unstable environments. For example, genuinely wearable electronics devices would be worn like clothing and move freely with bodily motion, which is only possible with flexible electronics.

Developing such electronics is challenging as almost all electronics are ridged by nature. This rigidity comes from the materials that electronic components are made from, and these materials are used as they provide the electrical characteristics needed. Therefore, creating flexible electronic components and designs requires using materials that have desirable electrical properties that are also flexible.

Since desirable electrical characteristics typically come from crystalline structures, most electrical materials are far from being flexible. However, a few are indeed flexible while having electrical properties, and most are based on polymers and organic components or a combination of both.

Creating devices from flexible electronic materials presents a range of challenges. One of these is that creating circuits using such materials is often different from creating traditional components such as semiconductors. As such, the creation of flexible electronics usually requires specialist machinery that is not widely available. Another challenge of developing flexible electronics is the inability to shrink active components (i.e. transistors), to make practical circuits. Even though micron features can be achieved, such a circuit cannot integrate wireless communication, hold large memory spaces for applications, and operate at high speeds.

Researchers develop a new transfer method for creating printed electronics

Researchers from the Daegu Gyeongbuk Institute of Science and Technology (DGIST) in Korea have recently developed a new technique for transferring printed designs onto a flexible substrate. The research team are the first to have developed a dry process that requires minimal equipment while also being achievable on both small and large scale.

The process is very similar to the toner transfer method commonly used on DIY PCBs. Simply put, a circuit design is placed onto a silicon wafer using standard practices (i.e. ion sputtering and layer etching). From there, the flexible substrate is placed over the design, and the sandwich structure is heated up.

After a few seconds of heating, the sandwich is cooled, which causes the silicon substrate to shrink at a different rate to the circuit design and flexible substrate. Thus, cracks form between the silicon substrate and the circuit design, causing the design to adhere to the flexible substrate.

Will the new method help design flexible electronics?

According to the researchers, the new method provides multiple advantages to traditional methods for designing circuits on flexible substrates. Firstly, using a solid silicon wafer substrate enables accurate positioning of designs onto the flexible substrates. Secondly, the transfer time is a few seconds which is significantly faster than standard processes using wet inks and chemicals to create layers.

Furthermore, the researchers demonstrated the capabilities of their process by constructing multiple functioning devices, including an optogenetic probe, a wireless power antenna, and a gas sensor. This shows that the device can be used practically, and the simplicity of the process demonstrates that it could be commercially viable.

Research such as the new transfer method help to progress the development of practical, flexible electronics. However, when precisely flexible electronics become practical and commercial is unknown.