A world’s first in developments of bioelectronics has been showcased by researchers at Linkoping University (LiU) in Sweden. The new research has demonstrated complementary electrochemical logic circuits that can function for long periods in water.

The team of researchers at the Laboratory of Organic Electronics (LOE), including head of research in the organic nanoelectronics group Simone Fabiano, has published its latest findings in an article in Advanced Materials. The LOE focus its research on electronic and optical properties of organic materials and organic-inorganic hybrid systems.

Researchers at LiU developed the first printable organic electrochemical transistors back in 2002; and, since then, various organic electronic components have become widely available, including LEDs and electromagnetic displays.

One of the primary stumbling blocks to the latest developments has been finding a stable-enough polymer to operate in water and also sustain a high current when the material is doped. Previously, materials used were p-type, in which charge carriers are holes. With electrons as charge carriers, n-type materials function better as a complementary material.

In their published article, the team presents results from using the n-type conduction material BBL [poly(benzimidazobenzophenanthroline)] with a beneficial ladder-type structure favoring ambient stability and high currents when doped. This material is more commonly utilized in solar cell research.

Another of the researchers from LiU, postdoctoral researcher Hengda Sun, has found a technique to create thick films of the material. “We have used spray coating to produce films up to 200nm thick,” said Fabiano.“These can reach extremely high conductivities.” An advantage of the greater thickness is the greater conductivity. Also, Sun has demonstrated that these circuits function for long periods of time in the presence of oxygen and water.

These developments are very exciting, according to Fabiano “This may appear at first glance to be a small advance in a specialized field, but what is great about it is that it has major consequences for many applications. We can now construct complementary logic circuits—inverters, sensors and other components—that function in moist surroundings.”

“Resistors are needed in logical circuits that are based solely on p-type electrochemical transistors,” said Magnus Berggren, head of the laboratory of organic electronics. “These are rather bulky, and this limits the applications that can be achieved. With an n-type material in our toolbox, we can produce complementary circuits that occupy the available space much more efficiently, since resistors are no longer required in the logical circuits.”

Along with being applicable in the field of bioelectronics, there are many applications for these organic components, including printable logic circuits, sensors and flexible displays.

You can read more about the LiU research featured in Advanced Materials here or on the LOE’s website here.