Tag Archives: Ali Khademhosseini

Flexible graphene-rubber sensor for wearables

Courtesy: University of Waterloo

This waffled, greyish thing may not look like much but scientists are hopeful that it can be useful as a health sensor in athletic shoes and elsewhere. A March 6, 2020 news item on Nanowerk describes the work in more detail (Note: Links have been removed),

Researchers have utilized 3D printing and nanotechnology to create a durable, flexible sensor for wearable devices to monitor everything from vital signs to athletic performance (ACS Nano, “3D-Printed Ultra-Robust Surface-Doped Porous Silicone Sensors for Wearable Biomonitoring”).

The new technology, developed by engineers at the University of Waterloo [Ontario, Canada], combines silicone rubber with ultra-thin layers of graphene in a material ideal for making wristbands or insoles in running shoes.

A March 6, 2020 University of Waterloo news release, which originated the news item, delves further,

When that rubber material bends or moves, electrical signals are created by the highly conductive, nanoscale graphene embedded within its engineered honeycomb structure.

“Silicone gives us the flexibility and durability required for biomonitoring applications, and the added, embedded graphene makes it an effective sensor,” said Ehsan Toyserkani, research director at the Multi-Scale Additive Manufacturing (MSAM) Lab at Waterloo. “It’s all together in a single part.”

Fabricating a silicone rubber structure with such complex internal features is only possible using state-of-the-art 3D printing – also known as additive manufacturing – equipment and processes.

The rubber-graphene material is extremely flexible and durable in addition to highly conductive.

“It can be used in the harshest environments, in extreme temperatures and humidity,” said Elham Davoodi, an engineering PhD student at Waterloo who led the project. “It could even withstand being washed with your laundry.”

The material and the 3D printing process enable custom-made devices to precisely fit the body shapes of users, while also improving comfort compared to existing wearable devices and reducing manufacturing costs due to simplicity.

Toyserkani, a professor of mechanical and mechatronics engineering, said the rubber-graphene sensor can be paired with electronic components to make wearable devices that record heart and breathing rates, register the forces exerted when athletes run, allow doctors to remotely monitor patients and numerous other potential applications.

Researchers from the University of California, Los Angeles and the University of British Columbia collaborated on the project.

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

3D-Printed Ultra-Robust Surface-Doped Porous Silicone Sensors for Wearable Biomonitoring by Elham Davoodi, Hossein Montazerian, Reihaneh Haghniaz, Armin Rashidi, Samad Ahadian, Amir Sheikhi, Jun Chen, Ali Khademhosseini, Abbas S. Milani, Mina Hoorfar, Ehsan Toyserkani. ACS Nano 2020, 14, 2, 1520-1532 DOI: https://doi.org/10.1021/acsnano.9b06283 Publication Date: January 6, 2020 Copyright © 2020 American Chemical Society

This paper is behind a paywall.

Stretchy optical materials for implants that could pulse light

An Oct. 17, 2016 Massachusetts Institute of Technology (MIT) news release (also on EurekAlert) by Emily Chu describes research that could lead to long-lasting implants offering preventive health strategies,

Researchers from MIT and Harvard Medical School have developed a biocompatible and highly stretchable optical fiber made from hydrogel — an elastic, rubbery material composed mostly of water. The fiber, which is as bendable as a rope of licorice, may one day be implanted in the body to deliver therapeutic pulses of light or light up at the first sign of disease. [emphasis mine]

The researchers say the fiber may serve as a long-lasting implant that would bend and twist with the body without breaking down. The team has published its results online in the journal Advanced Materials.

Using light to activate cells, and particularly neurons in the brain, is a highly active field known as optogenetics, in which researchers deliver short pulses of light to targeted tissues using needle-like fibers, through which they shine light from an LED source.

“But the brain is like a bowl of Jell-O, whereas these fibers are like glass — very rigid, which can possibly damage brain tissues,” says Xuanhe Zhao, the Robert N. Noyce Career Development Associate Professor in MIT’s Department of Mechanical Engineering. “If these fibers could match the flexibility and softness of the brain, they could provide long-term more effective stimulation and therapy.”

Getting to the core of it

Zhao’s group at MIT, including graduate students Xinyue Liu and Hyunwoo Yuk, specializes in tuning the mechanical properties of hydrogels. The researchers have devised multiple recipes for making tough yet pliable hydrogels out of various biopolymers. The team has also come up with ways to bond hydrogels with various surfaces such as metallic sensors and LEDs, to create stretchable electronics.

The researchers only thought to explore hydrogel’s use in optical fibers after conversations with the bio-optics group at Harvard Medical School, led by Associate Professor Seok-Hyun (Andy) Yun. Yun’s group had previously fabricated an optical fiber from hydrogel material that successfully transmitted light through the fiber. However, the material broke apart when bent or slightly stretched. Zhao’s hydrogels, in contrast, could stretch and bend like taffy. The two groups joined efforts and looked for ways to incorporate Zhao’s hydrogel into Yun’s optical fiber design.

Yun’s design consists of a core material encased in an outer cladding. To transmit the maximum amount of light through the core of the fiber, the core and the cladding should be made of materials with very different refractive indices, or degrees to which they can bend light.

“If these two things are too similar, whatever light source flows through the fiber will just fade away,” Yuk explains. “In optical fibers, people want to have a much higher refractive index in the core, versus cladding, so that when light goes through the core, it bounces off the interface of the cladding and stays within the core.”

Happily, they found that Zhao’s hydrogel material was highly transparent and possessed a refractive index that was ideal as a core material. But when they tried to coat the hydrogel with a cladding polymer solution, the two materials tended to peel apart when the fiber was stretched or bent.

To bond the two materials together, the researchers added conjugation chemicals to the cladding solution, which, when coated over the hydrogel core, generated chemical links between the outer surfaces of both materials.

“It clicks together the carboxyl groups in the cladding, and the amine groups in the core material, like molecular-level glue,” Yuk says.

Sensing strain

The researchers tested the optical fibers’ ability to propagate light by shining a laser through fibers of various lengths. Each fiber transmitted light without significant attenuation, or fading. They also found that fibers could be stretched over seven times their original length without breaking.

Now that they had developed a highly flexible and robust optical fiber, made from a hydrogel material that was also biocompatible, the researchers began to play with the fiber’s optical properties, to see if they could design a fiber that could sense when and where it was being stretched.

They first loaded a fiber with red, green, and blue organic dyes, placed at specific spots along the fiber’s length. Next, they shone a laser through the fiber and stretched, for instance, the red region. They measured the spectrum of light that made it all the way through the fiber, and noted the intensity of the red light. They reasoned that this intensity relates directly to the amount of light absorbed by the red dye, as a result of that region being stretched.

In other words, by measuring the amount of light at the far end of the fiber, the researchers can quantitatively determine where and by how much a fiber was stretched.

“When you stretch a certain portion of the fiber, the dimensions of that part of the fiber changes, along with the amount of light that region absorbs and scatters, so in this way, the fiber can serve as a sensor of strain,” Liu explains.

“This is like a multistrain sensor through a single fiber,” Yuk adds. “So it can be an implantable or wearable strain gauge.”

The researchers imagine that such stretchable, strain-sensing optical fibers could be implanted or fitted along the length of a patient’s arm or leg, to monitor for signs of improving mobility.

Zhao envisions the fibers may also serve as sensors, lighting up in response to signs of disease.

“We may be able to use optical fibers for long-term diagnostics, to optically monitor tumors or inflammation,” he says. “The applications can be impactful.”

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

Highly Stretchable, Strain Sensing Hydrogel Optical Fibers by Jingjing Guo, Xinyue Liu, Nan Jiang, Ali K. Yetisen, Hyunwoo Yuk, Changxi Yang, Ali Khademhosseini, Xuanhe Zhao, and Seok-Hyun Yun. Advanced Materials DOI: 10.1002/adma.201603160 Version of Record online: 7 OCT 2016

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Sutures that can gather data wirelessly

Are sutures which gather data hackable? It’s a little early to start thinking about that issue as this seems to be brand new research. A July 18, 2016 news item on ScienceDaily tells more,

For the first time, researchers led by Tufts University engineers have integrated nano-scale sensors, electronics and microfluidics into threads — ranging from simple cotton to sophisticated synthetics — that can be sutured through multiple layers of tissue to gather diagnostic data wirelessly in real time, according to a paper published online July 18 [2016] in Microsystems & Nanoengineering. The research suggests that the thread-based diagnostic platform could be an effective substrate for a new generation of implantable diagnostic devices and smart wearable systems.

A July 18, 2016 Tufts University news release (also on EurekAlert), which originated the news item, provides more detail,

The researchers used a variety of conductive threads that were dipped in physical and chemical sensing compounds and connected to wireless electronic circuitry to create a flexible platform that they sutured into tissue in rats as well as in vitro. The threads collected data on tissue health (e.g. pressure, stress, strain and temperature), pH and glucose levels that can be used to determine such things as how a wound is healing, whether infection is emerging, or whether the body’s chemistry is out of balance. The results were transmitted wirelessly to a cell phone and computer.

The three-dimensional platform is able to conform to complex structures such as organs, wounds or orthopedic implants.

While more study is needed in a number of areas, including investigation of long-term biocompatibility, researchers said initial results raise the possibility of optimizing patient-specific treatments.

“The ability to suture a thread-based diagnostic device intimately in a tissue or organ environment in three dimensions adds a unique feature that is not available with other flexible diagnostic platforms,” said Sameer Sonkusale, Ph.D., corresponding author on the paper and director of the interdisciplinary Nano Lab in the Department of Electrical and Computer Engineering at Tufts School of Engineering. “We think thread-based devices could potentially be used as smart sutures for surgical implants, smart bandages to monitor wound healing, or integrated with textile or fabric as personalized health monitors and point-of-care diagnostics.”

Until now, the structure of substrates for implantable devices has essentially been two-dimensional, limiting their usefulness to flat tissue such as skin, according to the paper. Additionally, the materials in those substrates are expensive and require specialized processing.

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

A toolkit of thread-based microfluidics, sensors, and electronics for 3D tissue embedding for medical diagnostics by Pooria Mostafalu, Mohsen Akbari, Kyle A. Alberti, Qiaobing Xu, Ali Khademhosseini, & Sameer R. Sonkusale. Microsystems & Nanoengineering 2, Article number: 16039 (2016) doi:10.1038/micronano.2016.39 Published online 18 July 2016

This paper is open access.

Using Google Glass to monitor organs-on-chips

Google Glass : Explorer version Credit: Dan Leveille, twitter.com/danlev Courtesty: Wikimedi

Google Glass: Explorer Edition Credit: Dan Leveille, twitter.com/danlev Courtesy: Wikimedia

Researchers have introduced Google Glass as a new application for monitoring and controlling organs-on-chips according to a March 18, 2016 news item on ScienceDaily,

Investigators from Brigham and Women’s Hospital (BWH [Boston, Massachussetts]) have developed hardware and software to remotely monitor and control devices that mimic the human physiological system. Devices known as organs-on-chips allow researchers to test drug compounds and predict physiological responses with high accuracy in a laboratory setting. But monitoring the results of such experiments from a conventional desktop computer has several limitations, especially when results must be monitored over the course of hours, days or even weeks.

Google Glass, one of the newest forms of wearable technology, offers researchers a hands-free and flexible monitoring system. To make Google Glass work for their purposes, Zhang et al. custom developed hardware and software that takes advantage of voice control command (“ok glass”) and other features in order to not only monitor but also remotely control their liver- and heart-on-a-chip systems. Using valves remotely activated by the Glass, the team introduced pharmaceutical compounds on liver organoids and collected the results. …

A March 18, 2016 BWH press release on EurekAlert, which originated the news item, describes the hopes for this new combined platform,

“We believe such a platform has widespread applications in biomedicine, and may be further expanded to health care settings where remote monitoring and control could make things safer and more efficient,” said senior author Ali Khademhosseini, PhD, Director of the Biomaterials Innovation Research Center at BWH.

“This may be of particular importance in cases where experimental conditions threaten human life – such as work involving highly pathogenic bacteria or viruses or radioactive compounds,” said leading author, Shrike Zhang, PhD, also of BWH’s Biomedical Division.

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

Google Glass-Directed Monitoring and Control of Microfluidic Biosensors and Actuators by Yu Shrike Zhang, Fabio Busignani, João Ribas, Julio Aleman, Talles Nascimento Rodrigues, Seyed Ali Mousavi Shaegh, Solange Massa, Camilla Baj Rossi, Irene Taurino, Su-Ryon Shin, Giovanni Calzone, Givan Mark Amaratunga, Douglas Leon Chambers, Saman Jabari, Yuxi Niu, Vijayan Manoharan, Mehmet Remzi Dokmeci, Sandro Carrara, Danilo Demarchi, & Ali Khademhossein. Scientific Reports 6, Article number: 22237 (2016) doi:10.1038/srep22237 Published online: 01 March 2016

This paper is open access.