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Next-generation human bionics: what goes on inside organic transistors?

16th April 2019

Once the domain of TVs and smart devices, organic transistors may soon become critical components for the development of next-generation human bionics.

PhD candidate Joshua Arthur received a 2019 Endeavour Research Leadership Award to progress his work on understanding organic thin-film transistor (OTFT) technology capable of receiving biological signals.

Modes of communication in electronic devices and the human body are intrinsically different.

Electronic interface devices that can seamlessly integrate with the human body have the potential to transform prosthetics into bioelectronic devices which mimic the functions of a real limb.

“Hypothetically we would use these organic transistors to intercept the biological signals and tell us information about what is happening in that system,” Joshua said.

Communication in electronic devices is achieved through the flow of electrons while communication in the human body is established through the exchange of ions (Na+, K+, etc.) and protons (H+).

Protons serve as intercellular messengers involved in essential biological processes, including muscle contraction, brain function and taste reception.

Within the cell, proton gradients drive the production of adenosine triphosphate (ATP), an important organic molecule that provides energy for cellular function.

Over the next two years, Joshua will study the physics of bioelectronic transistors to gain a fundamental understanding of how they work by focusing on the material, optical and electronic properties.

“There are gaps in what we know about how these organic transistors can sense protons.

“At the moment, I’m working to refine our transistors to be more robust and reliable, before I can thoroughly explore the mechanisms.

“Our sensors are based on a type of OTFT with very promising characteristics but still in the early stages of development for sensing applications.

Organic materials in OTFT are carbon-based compounds but not necessarily of biological origin, even though the vast majority of biological molecules are carbon-based such as proteins, hormones and DNA, according to Joshua.

“Organic materials are biocompatible, soft and flexible, and are able to interface with soft biological surfaces.

“An OTFT functions as an electronic switch and amplifier of signals.

“Most transistors aren’t sensors. We take advantage of the amplification properties by allowing protons to interact with an organic layer, producing a measurable change in current.

“Organic sensors could be implanted or used on the skin surface to analyse fluids they come into contact with.

While applications of new bioelectronic transistors are not currently specialised, Joshua said the organic devices have various potential biomedical applications.

“My goal is to do to the preliminary work of understanding these devices, which is an essential step toward making biological applications.”

An image of mesoporous nanoparticle films as a gate in an OTFT. Images were taken using a helium ion microscope and published in A highly porous and conductive composite gate electrode for OTFT sensors.
An image of mesoporous nanoparticle films as a gate in an OTFT. Images were taken using a helium ion microscope and published in “A highly porous and conductive composite gate electrode for OTFT sensors”.


The transistors used for Joshua’s research use mesoporous silica Nanoparticles — one of the best solid-state proton conducting materials, according to his PhD supervisor Dr Soniya Yambem who conducts research on optoelectronic and bioelectronic devices in the QUT Science and Engineering Faculty.

“We know the transistors work as a sensor but we don’t understand how these work — that is what Joshua is investigating.

“We are capable of making the transistors extremely small and flexible which makes them ideal for bio-interfacing applications but, for our current investigations, we only need to make them millimetres wide and micrometres thick.

“Organic electronic devices can be flexible, stretchable and light as a feather, which makes them highly applicable for wearable technologies that conform to the shape and surface of the human body.

“Investigating these applications also led to my research in bioelectronics where devices integrate with the human body — biology and electronics integrating together.

“I generally tell people to think of Luke Skywalker’s prosthetic hand that can be controlled perfectly by his brain. The most critical interface is where the electronics join the human part of his body — the interface has to be soft and flexible, biocompatible so it won’t be rejected by the body, and capable of healing by itself and communicating properly with the human body.

“If the prosthetic feels excessive heat, for example, it should tell your brain to remove it from that heat.

“This outcome is currently difficult to achieve because electronics and the human body speak different languages, so we need a transducer (interpreter) in between.

Joshua and Dr Yambem will continue device study at the Central Analytic Research Facility (CARF) within the QUT Institute for Future Environments (IFE) this year before Joshua heads to Queen’s University in Canada, which houses experimental microscopy equipment capable of looking at the device operations in real time.

“We are not sensing biological interactions at this point — just detecting protons in laboratory conditions,” Joshua said

“Once it’s refined and reliability is ensured, we will map the protons moving inside the device and how these interact with organic film.

“We will measure the change in the electric current across the device, which could be connected to a visual device or other interface to display the output.”

“Experimental optical techniques will give us insight into operating mechanisms of how protons are detected by the transistor,” Joshua said.

Joshua discovered organic electronics during his capstone project in the final year of his Bachelor of Science (Physics) in 2017.

Dr Yambem was his supervisor. She later introduced him to Professor Jean-Michel Nunzi, a Tier 1 Canada Research Chair in Chiral Photonics at Queen’s University.

Professor Nunzi is an expert in organic device design and characterisation, and developed an original characterisation system to evaluate the optical and electronic properties of organic devices under a microscope.

Joshua will work under the supervision of Professor Nunzi while working in his lab for the Endeavour Research Leadership Award collaboration.

Learn more about this research

A highly porous and conductive composite gate electrode for OTFT sensors

Sulfonated Mesoporous Silica as Proton Exchanging Layer in SolidState Organic Transistor