In a presentation made at the 243rd National Meeting & Exposition of the American Chemical Society (ACS) in San Diego on March 26, Dr. John A. Rogers explained how “electronic skin” patches similar to the temporary tattoos children stick on their arms for fun may one day monitor and wirelessly diagnose health problems or deliver medication.
Dr. Rogers, Swanlund Chair, Professor of Materials Science and Engineering, Professor of Chemistry, Director, F. Seitz Materials Research Laboratory at the University of Illinois at Urbana-Champaign, Illinois said the patches have potential to eliminate the need for patients to stay tethered to large machines in a doctor’s office or hospital room for hours of treatment or monitoring. He noted that each year, hundreds of thousands of patients worldwide have electroencephalograms, electrocardiograms and electromyograms to check the health of their brains, hearts or muscles.
These procedures are uncomfortable, Dr. Rogers explained, leaving patients tethered to machines for hours at a time, cumbered with wires or pins adhering to the skin with gels or tape that can be painful to remove and can leave a sticky residue. More importantly, the tests detect brain, heart and muscle activity while patients are in a medical setting, rather than while they’re carrying out activities of everyday life.
“A key feature of our epidermal electronics is its natural interface to the body, without wires, pins, adhesives or gels, to allow a much more comfortable and functional system,” said Dr. Rogers. “The technology can be used to monitor brain, heart or muscle activity in a completely noninvasive way, while a patient is at home.”
The electronic skin patches are about the thickness of a human hair, and wearers cant feel them on their skin. They could even be covered up with a real temporary tattoo. Despite their minuscule dimensions, the patches can pack full-scale electronic circuits needed to monitor health status with wireless capabilities that can, with future development, be used to transmit data to the patients cell phone and on to the doctor’s office.
A paper published in the journal Nature Nanotechnology, entitled “Multifunctional wearable devices for diagnosis and therapy of movement disorders” (Nature Nanotechnology (2014) doi:10.1038/nnano.2014.38 Published online 30 March 2014), co-authored by Donghee Son, Jongha Lee, Shutao Qiao, Roozbeh Ghaffari, Jaemin Kim, Ji Eun Lee, Changyeong Song, Seok Joo Kim, Dong Jun Lee, Samuel Woojoo Jun, Shixuan Yang, Minjoon Park, Jiho Shin, Kyungsik Do, Mincheol Lee, Kwanghun Kang, Cheol Seong Hwang, Nanshu Lu, Taeghwan Hyeon, and Dae-Hyeong Kim, notes that wearable systems that monitor muscle activity, store data and deliver feedback therapy are the next frontier in personalized medicine and healthcare.
However, the researchers observe that technical challenges, such as fabrication of high-performance, energy-efficient sensors and memory modules that are in intimate mechanical contact with soft tissues, in conjunction with controlled delivery of therapeutic agents, limit the wide-scale adoption of such systems.
The Nature Nanotechnology paper coauthors describe materials, mechanics and designs for multifunctional, wearable-on-the-skin systems that address these challenges via monolithic integration of nanomembranes fabricated with a top-down approach, nanoparticles assembled by bottom-up methods, and stretchable electronics on a tissue-like polymeric substrate. Representative examples of such systems include physiological sensors, non-volatile memory and drug-release actuators. Quantitative analyses of the electronics, mechanics, heat-transfer and drug-diffusion characteristics validate the operation of individual components, thereby enabling system-level multifunctionalities.
Dr. Rogers and colleagues at the University of Illinois at Urbana-Champaign have developed patches that are not only be flexible, but stretchable, in order to to move with the natural motions of the skin as people go about their normal daly activities. To achieve these characteristics was a major challenge, however. The silicon-based wafers that are typically used in consumer electronics, such as laptops, tablets, and smartphones are hard and brittle, like glass. In order to graft their function into a material that bends and stretches like skin or rubber, the scientists had to use very small pieces in a wavy pattern, thereby structuring the system in a strategic way that would avoid any strains or stresses that would crack or fracture the tiny bits of silicon, D. Rogers explains.
The patches are transferred to the skin just like a temporary tattoo, with water and a backing that peels off. The first versions wore off after a day, or sooner if they became wet. However, the latest version is applied in the same way, but a modified form of the spray-on bandages sold in drugstores is applied over the patch. The spray protects the circuit from water and normal wear-and-tear and keeps it on the skin for up to a week. In this format, the devices can accommodate transpiration, sweat and even washing with soapy water.
“We’ve also figured out how to make the devices operate in a bi-directional way,” Dr. Rogers says. “The older devices only measure what’s going on in the body. Our newest patch can measure muscle activity and stimulate the muscles. That’s useful for rehabilitation after an accident or long periods of bed rest or even for helping people move prosthetic limbs more easily. And with plans to add Wi-Fi capabilities, electronic skin could also send information back to a physician.”
The Rogers Research Group at the University of Illinois at Urbana-Champaign focuses its research on development in electronic materials for devices that have unusual properties, including those that match the soft, curvilinear surfaces biological tissues for advanced surgical tools, wearable monitors and other biomedical systems
The Rogers team seeks to understand and exploit interesting characteristics of ‘soft’ materials, such as polymers, liquid crystals, and biological tissues as well as hybrid combinations of them with unusual classes of micro/nanomaterials, in the form of ribbons, wires, membranes, tubes or related. Their aim is to control and induce novel electronic and photonic responses in these materials; we also develop new ‘soft lithographic’ and biomimetic approaches for patterning them and guiding their growth. This work combines fundamental studies with forward-looking engineering efforts in a way that promotes positive feedback between the two. The lab’s current research focuses on soft materials for conformal electronics, nanophotonic structures, microfluidic devices, and microelectromechanical systems, all lately with an emphasis on bio-inspired and bio-integrated technologies — all highly multidisciplinary efforts that combine expertise from nearly every traditional field of technical study.
A company Dr. Rogers co-founded called mc10 is going a step further and putting the patches on medical instruments that go inside the body, such as catheters — the balloon-like tubes used in heart surgery. An electronic skin patch is placed on the outside surface of the catheter. When the catheter expands in the heart, the patch expands with it and touches the inside of the heart, taking measurements used to guide surgery.
Professor Rogers, who obtained his BA and BS degrees in chemistry and in physics from the University of Texas, Austin, in 1989, says the patches also could have applications in other areas useful for the consumer. For example, new devices allow monitoring and depth-profiling of skin hydration, with relevance in sports, skin-care and cosmetics, alike.
One of the Nature Nanotechnology paper coauthors, an associate and former student of Dr. Rogers, Dr. Dae-Hyeong Kim Ph.D., is now an Assistant Professor of the School of Chemical and Biological Engineering at Seoul National University. Dr. Kim was recently listed in “TR 35, 35 young innovators to change the world” by Technology Review, a magazine published by Massachusetts Institute of Technology. TR 35 refers to young scientists or engineers under the age of 35 working on innovative research. Dr. Kim, the second Korean engineer to be listed since 2008, was recognized for developing a technology to detect signals from heart and brain more accurately than existing equipment. To detect the signals from those organs, the transmitter must be flexible enough to bend along the curves of the organs. Professor Kim developed bendable, stretchable high performance silicon electronics to detect subtle changes in human physiology, and noted that experiments on animals have been conducted successfully, and the technology will be a great help to epilepsy or arrhythmia patients if it is launched.
Dr. Kim and Dr. Rogers were also co-authors with Nanshu Lu of the Department of Aerospace Engineering and Engineering Mechanics at the University of Texas at Austin and Roozbeh Ghaffari of MC10 Inc.atCambridge, Massachusetts of a 2012 paper published in the journal, NPG Asia Materials, titled “Inorganic semiconductor nanomaterials for flexible and stretchable bio-integrated electronics” (NPG Asia Materials (2012) 4, e15; doi:10.1038/am.2012.27 Published online 20 April 2012) in which they explain that rapid advances in semiconductor nanomaterials, techniques for their assembly, and strategies for incorporation into functional systems now enable sophisticated modes of functionality and corresponding use scenarios in electronics that cannot be addressed with conventional, wafer-based technologies.
The paper is a short review highlighting enabling developments in the synthesis of one- and two-dimensional semiconductor nanomaterials, their manipulation and use in various device components together with concepts in mechanics that allow integration onto flexible plastic foils and stretchable rubber sheets — examples of systems that combine with or are inspired by biology illustrate the current state-of-the-art in this fast-moving field.
The American Chemical Society (ACS)
The University of Illinois at Urbana-Champaign
Seoul National University
NPG Asia Materials
The University of Illinois at Urbana-Champaign
Seoul National University