Tag Archives: Deji Akinwande

Treating cardiac arrhythmia with light: a graphene tattoo

An April 17, 2023 news item on Nanowerk announced research into a graphene cardiac implant/tattoo,

Researchers led by Northwestern University and the University of Texas at Austin (UT) have developed the first cardiac implant made from graphene, a two-dimensional super material with ultra-strong, lightweight and conductive properties.

Similar in appearance to a child’s temporary tattoo, the new graphene “tattoo” implant is thinner than a single strand of hair yet still functions like a classical pacemaker. But unlike current pacemakers and implanted defibrillators, which require hard, rigid materials that are mechanically incompatible with the body, the new device softly melds to the heart to simultaneously sense and treat irregular heartbeats. The implant is thin and flexible enough to conform to the heart’s delicate contours as well as stretchy and strong enough to withstand the dynamic motions of a beating heart.

Caption: Graphene implant on tattoo paper. Credit: Ning Liu/University of Texas at Austin

An April 17, 2023 Northwestern University news release (also on EurekAlert), which originated the news item, provides more detail about the research, graphene, and the difficulties of monitoring a beating heart, Note: Links have been removed,

After implanting the device into a rat model, the researchers demonstrated that the graphene tattoo could successfully sense irregular heart rhythms and then deliver electrical stimulation through a series of pulses without constraining or altering the heart’s natural motions. Even better: The technology also is optically transparent, allowing the researchers to use an external source of optical light to record and stimulate the heart through the device.

The study will be published on Thursday (April 20 [2023]) in the journal Advanced Materials. It marks the thinnest known cardiac implant to date.

“One of the challenges for current pacemakers and defibrillators is that they are difficult to affix onto the surface of the heart,” said Northwestern’s Igor Efimov, the study’s senior author. “Defibrillator electrodes, for example, are essentially coils made of very thick wires. These wires are not flexible, and they break. Rigid interfaces with soft tissues, like the heart, can cause various complications. By contrast, our soft, flexible device is not only unobtrusive but also intimately and seamlessly conforms directly onto the heart to deliver more precise measurements.”

An experimental cardiologist, Efimov is a professor of biomedical engineering at Northwestern’s McCormick School of Engineering and professor of medicine at Northwestern University Feinberg School of Medicine. He co-led the study with Dmitry Kireev, a research associate at UT. Zexu Lin, a Ph.D. candidate in Efimov’s laboratory, is the paper’s first author.

Miracle material

Known as cardiac arrhythmias, heart rhythm disorders occur when the heart beats either too quickly or too slowly. While some cases of arrhythmia are not serious, many cases can lead to heart failure, stroke and even sudden death. In fact, complications related to arrythmia claim about 300,000 lives annually in the United States. Physicians commonly treat arrhythmia with implantable pacemakers and defibrillators that detect abnormal heartbeats and then correct rhythm with electrical stimulation. While these devices are lifesaving, their rigid nature may constrain the heart’s natural motions, injure soft tissues, cause temporary discomfort and induce complications, such as painful swelling, perforations, blood clots, infection and more.

With these challenges in mind, Efimov and his team sought to develop a bio-compatible device ideal for conforming to soft, dynamic tissues. After reviewing multiple materials, the researchers settled on graphene, an atomically thin form of carbon. With its ultra-strong, lightweight structure and superior conductivity, graphene has potential for many applications in high-performance electronics, high-strength materials and energy devices.

“For bio-compatibility reasons, graphene is particularly attractive,” Efimov said. “Carbon is the basis of life, so it’s a safe material that is already used in different clinical applications. It also is flexible and soft, which works well as an interface between electronics and a soft, mechanically active organ.”

Hitting a beating target

At UT, study co-authors Dimitry Kireev and Deji Akinwande were already developing graphene electronic tattoos (GETs) with sensing capabilities. Flexible and weightless, their team’s e-tattoos adhere to the skin to continuously monitor the body’s vital signs, including blood pressure and the electrical activity of the brain, heart and muscles.

But, while the e-tattoos work well on the skin’s surface, Efimov’s team needed to investigate new methods to use these devices inside the body — directly onto the surface of the heart.

“It’s a completely different application scheme,” Efimov said. “Skin is relatively dry and easily accessible. Obviously, the heart is inside the chest, so it’s difficult to access and in a wet environment.”

The researchers developed an entirely new technique to encase the graphene tattoo and adhere it to the surface of a beating heart. First, they encapsulated the graphene inside a flexible, elastic silicone membrane — with a hole punched in it to give access to the interior graphene electrode. Then, they gently placed gold tape (with a thickness of 10 microns) onto the encapsulating layer to serve as an electrical interconnect between the graphene and the external electronics used to measure and stimulate the heart. Finally, they placed it onto the heart. The entire thickness of all layers together measures about 100 microns in total.

The resulting device was stable for 60 days on an actively beating heart at body temperature, which is comparable to the duration of temporary pacemakers used as bridges to permanent pacemakers or rhythm management after surgery or other therapies.

Optical opportunities

Leveraging the device’s transparent nature, Efimov and his team performed optocardiography — using light to track and modulate heart rhythm — in the animal study. Not only does this offer a new way to diagnose and treat heart ailments, the approach also opens new possibilities for optogenetics, a method to control and monitor single cells with light. 

While electrical stimulation can correct a heart’s abnormal rhythm, optical stimulation is more precise. With light, researchers can track specific enzymes as well as interrogate specific heart, muscle or nerve cells.

“We can essentially combine electrical and optical functions into one biointerface,” Efimov said. “Because graphene is optically transparent, we can actually read through it, which gives us a much higher density of readout.”

The University of Texas at Austin issued an April 18, 2023 news release and as you would expect the focus is on their researchers, Note 1: I’ve removed many but not all of the redundancies between the two news releases; Note 2: A link has been removed,

A new cardiac implant made from graphene, a two-dimensional super material with ultra-strong, lightweight and conductive properties, functions like a classic pacemaker with some major improvements.

A team led by researchers from The University of Texas at Austin and Northwestern University developed the implantable derivative from wearable graphene-based electronic tattoo, or e-tattoo – graphene biointerface. The device, detailed in the journal Advanced Materials, marks the thinnest known cardiac implant to date.

“It’s very exciting to take our e-tattoo technology and use it as an implantable device inside the body,” said Dmitry Kireev, a postdoctoral research associate in the lab of professor Deji Akinwande’s lab at UT Austin who co-led the research. “The fact that is much more compatible with the human body, lightweight, and transparent, makes this a more natural solution for people dealing with heart problems.”

Hitting a beating target

At UT Austin, Akinwande and his team had been developing e-tattoos using graphene for several years, with a variety of functions, including monitoring body signals. Flexible and weightless, their team’s e-tattoos adhere to the skin to continuously monitor the body’s vital signs, including blood pressure and the electrical activity of the brain, heart and muscles.

But, while the e-tattoos work well on the skin’s surface, the researchers needed to find new ways to deploy these devices inside the body — directly onto the surface of the heart.

“The conditions inside the body are very different compared to affixing a device to the skin, so we had to re-imagine how we package our e-tattoo technology,” said Akinwande, a professor in the Chandra Family Department of Electrical and Computer Engineering.  

The researchers developed an entirely new technique to encase the graphene tattoo and adhere it to the surface of a beating heart. …

Here’s a link to and a citation for the paper,

Graphene Biointerface for Cardiac Arrhythmia Diagnosis and Treatment by Zexu Lin, Dmitry Kireev, Ning Liu, Shubham Gupta, Jessica LaPiano, Sofian N. Obaid, Zhiyuan Chen, Deji Akinwande, Igor R. Efimov. Advanced Materials Volume 35, Issue 22 June 1, 2023 2212190 DOI: https://doi.org/10.1002/adma.202212190 First published online: 25 March 2023

This paper is open access.

Synaptic transistors for brainlike computers based on (more environmentally friendly) graphene

An August 9, 2022 news item on ScienceDaily describes research investigating materials other than silicon for neuromorphic (brainlike) computing purposes,

Computers that think more like human brains are inching closer to mainstream adoption. But many unanswered questions remain. Among the most pressing, what types of materials can serve as the best building blocks to unlock the potential of this new style of computing.

For most traditional computing devices, silicon remains the gold standard. However, there is a movement to use more flexible, efficient and environmentally friendly materials for these brain-like devices.

In a new paper, researchers from The University of Texas at Austin developed synaptic transistors for brain-like computers using the thin, flexible material graphene. These transistors are similar to synapses in the brain, that connect neurons to each other.

An August 8, 2022 University of Texas at Austin news release (also on EurekAlert but published August 9, 2022), which originated the news item, provides more detail about the research,

“Computers that think like brains can do so much more than today’s devices,” said Jean Anne Incorvia, an assistant professor in the Cockrell School of Engineering’s Department of Electrical and Computer Engineer and the lead author on the paper published today in Nature Communications. “And by mimicking synapses, we can teach these devices to learn on the fly, without requiring huge training methods that take up so much power.”

The Research: A combination of graphene and nafion, a polymer membrane material, make up the backbone of the synaptic transistor. Together, these materials demonstrate key synaptic-like behaviors — most importantly, the ability for the pathways to strengthen over time as they are used more often, a type of neural muscle memory. In computing, this means that devices will be able to get better at tasks like recognizing and interpreting images over time and do it faster.

Another important finding is that these transistors are biocompatible, which means they can interact with living cells and tissue. That is key for potential applications in medical devices that come into contact with the human body. Most materials used for these early brain-like devices are toxic, so they would not be able to contact living cells in any way.

Why It Matters: With new high-tech concepts like self-driving cars, drones and robots, we are reaching the limits of what silicon chips can efficiently do in terms of data processing and storage. For these next-generation technologies, a new computing paradigm is needed. Neuromorphic devices mimic processing capabilities of the brain, a powerful computer for immersive tasks.

“Biocompatibility, flexibility, and softness of our artificial synapses is essential,” said Dmitry Kireev, a post-doctoral researcher who co-led the project. “In the future, we envision their direct integration with the human brain, paving the way for futuristic brain prosthesis.”

Will It Really Happen: Neuromorphic platforms are starting to become more common. Leading chipmakers such as Intel and Samsung have either produced neuromorphic chips already or are in the process of developing them. However, current chip materials place limitations on what neuromorphic devices can do, so academic researchers are working hard to find the perfect materials for soft brain-like computers.

“It’s still a big open space when it comes to materials; it hasn’t been narrowed down to the next big solution to try,” Incorvia said. “And it might not be narrowed down to just one solution, with different materials making more sense for different applications.”

The Team: The research was led by Incorvia and Deji Akinwande, professor in the Department of Electrical and Computer Engineering. The two have collaborated many times together in the past, and Akinwande is a leading expert in graphene, using it in multiple research breakthroughs, most recently as part of a wearable electronic tattoo for blood pressure monitoring.

The idea for the project was conceived by Samuel Liu, a Ph.D. student and first author on the paper, in a class taught by Akinwande. Kireev then suggested the specific project. Harrison Jin, an undergraduate electrical and computer engineering student, measured the devices and analyzed data.

The team collaborated with T. Patrick Xiao and Christopher Bennett of Sandia National Laboratories, who ran neural network simulations and analyzed the resulting data.

Here’s a link to and a citation for the ‘graphene transistor’ paper,

Metaplastic and energy-efficient biocompatible graphene artificial synaptic transistors for enhanced accuracy neuromorphic computing by Dmitry Kireev, Samuel Liu, Harrison Jin, T. Patrick Xiao, Christopher H. Bennett, Deji Akinwande & Jean Anne C. Incorvia. Nature Communications volume 13, Article number: 4386 (2022) DOI: https://doi.org/10.1038/s41467-022-32078-6 Published: 28 July 2022

This paper is open access.

From the memristor to the atomristor?

I’m going to let Michael Berger explain the memristor (from Berger’s Jan. 2, 2017 Nanowerk Spotlight article),

In trying to bring brain-like (neuromorphic) computing closer to reality, researchers have been working on the development of memory resistors, or memristors, which are resistors in a circuit that ‘remember’ their state even if you lose power.

Today, most computers use random access memory (RAM), which moves very quickly as a user works but does not retain unsaved data if power is lost. Flash drives, on the other hand, store information when they are not powered but work much slower. Memristors could provide a memory that is the best of both worlds: fast and reliable.

He goes on to discuss a team at the University of Texas at Austin’s work on creating an extraordinarily thin memristor: an atomristor,

he team’s work features the thinnest memory devices and it appears to be a universal effect available in all semiconducting 2D monolayers.

The scientists explain that the unexpected discovery of nonvolatile resistance switching (NVRS) in monolayer transitional metal dichalcogenides (MoS2, MoSe2, WS2, WSe2) is likely due to the inherent layered crystalline nature that produces sharp interfaces and clean tunnel barriers. This prevents excessive leakage and affords stable phenomenon so that NVRS can be used for existing memory and computing applications.

“Our work opens up a new field of research in exploiting defects at the atomic scale, and can advance existing applications such as future generation high density storage, and 3D cross-bar networks for neuromorphic memory computing,” notes Akinwande [Deji Akinwande, an Associate Professor at the University of Texas at Austin]. “We also discovered a completely new application, which is non-volatile switching for radio-frequency (RF) communication systems. This is a rapidly emerging field because of the massive growth in wireless technologies and the need for very low-power switches. Our devices consume no static power, an important feature for battery life in mobile communication systems.”

Here’s a link to and a citation for the Akinwande team’s paper,

Atomristor: Nonvolatile Resistance Switching in Atomic Sheets of Transition Metal Dichalcogenides by Ruijing Ge, Xiaohan Wu, Myungsoo Kim, Jianping Shi, Sushant Sonde, Li Tao, Yanfeng Zhang, Jack C. Lee, and Deji Akinwande. Nano Lett., Article ASAP DOI: 10.1021/acs.nanolett.7b04342 Publication Date (Web): December 13, 2017

Copyright © 2017 American Chemical Society

This paper appears to be open access.

ETA January 23, 2018: There’s another account of the atomristor in Samuel K. Moore’s January 23, 2018 posting on the Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website).

An easier and cheaper way to make: wearable and disposable medical tattoolike patches

A Sept. 29, 2015 news item on ScienceDaily features an electronic health patch that’s cheaper and easier to make,

A team of researchers has invented a method for producing inexpensive and high-performing wearable patches that can continuously monitor the body’s vital signs for human health and performance tracking. The researchers believe their new method is compatible with roll-to-roll manufacturing.

The researchers have provided a photograph of a prototype patch,

Assitant professor Nanshu Lu and her team have developed a faster, inexpensive method for making epidermal electronics. Cockrell School of Engineering

Assitant professor Nanshu Lu and her team have developed a faster, inexpensive method for making epidermal electronics. Cockrell School of Engineering

A University of Texas at Austin Sept. 29, 2015 news release (also on EurekAlert), which originated the news item, provides more details,

Led by Assistant Professor Nanshu Lu, the team’s manufacturing method aims to construct disposable tattoo-like health monitoring patches for the mass production of epidermal electronics, a popular technology that Lu helped develop in 2011.

The team’s breakthrough is a repeatable “cut-and-paste” method that cuts manufacturing time from several days to only 20 minutes. The researchers believe their new method is compatible with roll-to-roll manufacturing — an existing method for creating devices in bulk using a roll of flexible plastic and a processing machine.

Reliable, ultrathin wearable electronic devices that stick to the skin like a temporary tattoo are a relatively new innovation. These devices have the ability to pick up and transmit the human body’s vital signals, tracking heart rate, hydration level, muscle movement, temperature and brain activity.

Although it is a promising invention, a lengthy, tedious and costly production process has until now hampered these wearables’ potential.

“One of the most attractive aspects of epidermal electronics is their ability to be disposable,” Lu said. “If you can make them inexpensively, say for $1, then more people will be able to use them more frequently. This will open the door for a number of mobile medical applications and beyond.”

The UT Austin method is the first dry and portable process for producing these electronics, which, unlike the current method, does not require a clean room, wafers and other expensive resources and equipment. Instead, the technique relies on freeform manufacturing, which is similar in scope to 3-D printing but different in that material is removed instead of added.

The two-step process starts with inexpensive, pre-fabricated, industrial-quality metal deposited on polymer sheets. First, an electronic mechanical cutter is used to form patterns on the metal-polymer sheets. Second, after removing excessive areas, the electronics are printed onto any polymer adhesives, including temporary tattoo films. The cutter is programmable so the size of the patch and pattern can be easily customized.

Deji Akinwande, an associate professor and materials expert in the Cockrell School, believes Lu’s method can be transferred to roll-to-roll manufacturing.

“These initial prototype patches can be adapted to roll-to-roll manufacturing that can reduce the cost significantly for mass production,” Akinwande said. “In this light, Lu’s invention represents a major advancement for the mobile health industry.”

After producing the cut-and-pasted patches, the researchers tested them as part of their study. In each test, the researchers’ newly fabricated patches picked up body signals that were stronger than those taken by existing medical devices, including an ECG/EKG, a tool used to assess the electrical and muscular function of the heart. The team also found that their patch conforms almost perfectly to the skin, minimizing motion-induced false signals or errors.

The UT Austin wearable patches are so sensitive that Lu and her team can envision humans wearing the patches to more easily maneuver a prosthetic hand or limb using muscle signals. For now, Lu said, “We are trying to add more types of sensors including blood pressure and oxygen saturation monitors to the low-cost patch.”

Here’s a link to and a citation for the paper,

“Cut-and-Paste” Manufacture of Multiparametric Epidermal Sensor Systems by Shixuan Yang, Ying-Chen Chen, Luke Nicolini, Praveenkumar Pasupathy, Jacob Sacks, Su Becky, Russell Yang, Sanchez Daniel, Yao-Feng Chang, Pulin Wang, David Schnyer, Dean Neikirk, and Nanshu Lu. Advanced Materials DOI: 10.1002/adma.201502386 First published: 23 September 2015

This paper is behind a paywall.