Sunday, October 1, 2023

Hybridisation and Thin-Film Sensors Key Enablers of Flexible Electronics Today

Abhishek A. Mutha is a senior technical correspondent at EFY

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Smart contact lens to inform diabetic patients on blood-glucose levels. A brilliant example of tackling a growing problem of diabetes using flexible and printed electronics is Google’s Smart Contact Lens project, co-developed by Google and Novartis.

Uncontrolled blood sugar poses a threat to people’s lives and could damage their eyes, kidneys or heart in the long run. People with diabetes, more often than not, have fluctuating glucose levels. Sudden spikes or drops are dangerous. To monitor the blood-glucose level, people with diabetes need to prick their finger and test drops of blood at regular intervals throughout the day.

In hopes of finding easier methods to measure glucose body levels, scientists have been researching on an alternate, non-invasive way in the form of measuring tears. With the help of miniaturised electronics, Google is testing a smart contact lens to measure glucose levels in tears using a tiny wireless chip and miniaturised glucose sensor embedded between two layers of soft contact lens material.

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This novel contact lens will contain a low-power microchip and a transparent ultra-thin and flexible electronic circuit, and will be used to measure blood-sugar levels of diabetes sufferers. Although these are still early days, Google is also planning to explore the possibility of integrating tiny LED lights to indicate to the user that glucose level has crossed or dropped below a certain threshold level.

Focus on hybrid and purely flexible systems. Most recently, research has also shifted towards system integration, notes Petti. System integration is developing in both the directions of hybrid integration of rigid conventional silicon technology with flexible/printed electronics, as well as the realisation of fully-flexible and/or printable platforms.

The best examples of hybrid system integration can be surely found in the research done by Prof. Rogers at University of Illinois. Areas include flexible, stretchable, epidermal and biodegradable sensors and circuits using conventional silicon technology and unconventional substrates and architectures.

On the other side, a notable example of the fully-flexible approach includes the work by ETH Zürich (or Swiss Federal Institute of Technology Zurich) on lightweight and transparent metal-oxide electronics that can wrap around a human hair. This can lead to fully-flexible and transparent smart contact lenses, as well as many other biomedical applications.

In the field of fully-flexible system integration, the biggest players are Interuniversity Microelectronics Centre (IMEC) and Holst Center, who offer an extensive organic and metal-oxide based technology for flexible thin-film transistors, circuits, photovoltaics and active-matrix organic light emitting diode (AMOLED) displays.

Notable universities involved in research. Globally, key universities in this field are almost too numerous to name with each group working on topics ranging from fundamental science all the way to final product characterisation and prove-out, feels Farnsworth.

He says, “Other than California Polytechnic State University, some other groups doing important work in the area include CPI in the UK, Cetemmsa Technological Centre near Barcelona, Spain, VTT Technical Research Centre in Finland, Fraunhofer group in Germany, Industrial Technology Research Institute (ITRI) in Taiwan, The National Institute of Advanced Industrial Science and Technology (AIST) in Japan and EMSE near Marseilles, France.”

He adds, “Dr Denis Cormier at Rochester Institute of Technology in Rochester, New York, is doing work combining printed electronics technologies with the still-developing additive manufacturing space.”

Flexible electronics will make a ripple in every possible field
From healthcare monitoring, wearable and skin-like electronics, smart packaging, sensory tags for medical and biomedical applications, security and mobility commerce to environmental and industrial electronics, many novel applications are being envisioned. Petti says, “This is all enabled by the unique selling points of flexible and printable electronics, which include its mechanical flexibility, large-area manufacturing and potential low-cost in volume.”

According to Cantarella, for printed and flexible electronics, the most challenging sector will be medical. He says, “The devices included in this field should be bio-compatible and sufficiently reliable for medical care in order to be able to generally improve healthcare and monitor physical conditions.”


“Even more challenging is the idea to implant such devices for real-time analysis such as digestible electronic components that can be dissolved in the human body,” adds Cantarella.

PragmatIC Printing holds a great deal of potential for the production of new exciting applications within the packaging sector and the development of the IoT.

Bagshaw notes, “The company is developing ultra-thin and low-cost flexible microcircuits that can be easily incorporated into mass-market packaging, and will revolutionise everyday living by providing consumers with real-time information about every aspect of their environment.”

He adds, “Hybrid electronics will give rise to a wide range of new, novel applications such as flexible displays for mobile devices, smart therapeutic bandages for managing and monitoring recovery of wounds, wearable electronics for monitoring and improving performance, wireless medical devices for rapid diagnostics using printed sensors, conformable lighting and intelligent packaging for consumer goods and industrial products, to name a few.”

At a printed electronics conference in the USA, it was predicted that the overall market for printed and flexible sensors is forecast to be worth over US$ 7 billion by 2020.


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