Tag Archives: Wei Wang

‘Superhemophobic’ medical implants

Counterintuitively, repelling blood is the concept behind a new type of medical implant according to a Jan. 18, 2017 news item on ScienceDaily,

Medical implants like stents, catheters and tubing introduce risk for blood clotting and infection — a perpetual problem for many patients.

Colorado State University engineers offer a potential solution: A specially grown, “superhemophobic” titanium surface that’s extremely repellent to blood. The material could form the basis for surgical implants with lower risk of rejection by the body.

Blood, plasma and water droplets beading on a superomniphobic surface. CSU researchers have created a superhemophobic titanium surface, repellent to blood, that has potential applications for biocompatible medical devices. Courtesy: Colorado State University

A Jan. 18, 2017 Colorado State University news release by Anne Ju Manning, which originated the news item, explains more,

t’s an outside-the-box innovation achieved at the intersection of two disciplines: biomedical engineering and materials science. The work, recently published in Advanced Healthcare Materials, is a collaboration between the labs of Arun Kota, assistant professor of mechanical engineering and biomedical engineering; and Ketul Popat, associate professor in the same departments.

Kota, an expert in novel, “superomniphobic” materials that repel virtually any liquid, joined forces with Popat, an innovator in tissue engineering and bio-compatible materials. Starting with sheets of titanium, commonly used for medical devices, their labs grew chemically altered surfaces that act as perfect barriers between the titanium and blood. Their teams conducted experiments showing very low levels of platelet adhesion, a biological process that leads to blood clotting and eventual rejection of a foreign material.

Chemical compatibility

A material “phobic” (repellent) to blood might seem counterintuitive, the researchers say, as often biomedical scientists use materials “philic” (with affinity) to blood to make them biologically compatible. “What we are doing is the exact opposite,” Kota said. “We are taking a material that blood hates to come in contact with, in order to make it compatible with blood.” The key innovation is that the surface is so repellent, that blood is tricked into believing there’s virtually no foreign material there at all.

The undesirable interaction of blood with foreign materials is an ongoing problem in medical research, Popat said. Over time, stents can form clots, obstructions, and lead to heart attacks or embolisms. Often patients need blood-thinning medications for the rest of their lives – and the drugs aren’t foolproof.

“The reason blood clots is because it finds cells in the blood to go to and attach,” Popat said. “Normally, blood flows in vessels. If we can design materials where blood barely contacts the surface, there is virtually no chance of clotting, which is a coordinated set of events. Here, we’re targeting the prevention of the first set of events.”

nanotubes

Fluorinated nanotubes provided the best superhemophobic surface in the researchers’ experiments.

The researchers analyzed variations of titanium surfaces, including different textures and chemistries, and they compared the extent of platelet adhesion and activation. Fluorinated nanotubes offered the best protection against clotting, and they plan to conduct follow-up experiments.

Growing a surface and testing it in the lab is only the beginning, the researchers say. They want to continue examining other clotting factors, and eventually, to test real medical devices.

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

Hemocompatibility of Superhemophobic Titania Surfaces by Sanli Movafaghi, Victoria Leszczak, Wei Wang, Jonathan A. Sorkin, Lakshmi P. Dasi, Ketul C. Popat, and Arun K. Kota. Advanced Healthcare Materials DOI: 10.1002/adhm.201600717 Version of Record online: 21 DEC 2016

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

Repelling liquid with superomniphobic tape

The Kota lab at Colorado State University has created a superomniphobic tape that adheres to any surface and imparts liquid-repellant properties. Credit: Kota lab/Colorado State University

The Kota lab at Colorado State University has created a superomniphobic tape that adheres to any surface and imparts liquid-repellant properties. Credit: Kota lab/Colorado State University

An Oct. 20, 2016 news item on ScienceDaily celebrates the creation of a liquid-repelling superomniphobic tape,

Arun Kota, assistant professor of mechanical engineering at Colorado State University, has made a superomniphobic tape that, when adhered to any surface, gives the surface liquid-repelling properties. This recent breakthrough has been published by the American Chemical Society.

An Oct. 20, 2016 Colorado State University news release on EurekAlert, which originated the news item, provides more description,

Superomniphobic surfaces are extremely repellent to all liquids, made possible by an air cushion that lies between a liquid and a solid surface. With more than 10 years of research in this area, Kota has made many breakthroughs in super-repellent coatings. This latest product is similar in flexibility to Scotch Tape, but has the additional functionality of being extremely liquid-repellant.

Kota, doctoral student Hamed Vahabi, and postdoctoral fellow Wei Wang, developed the unusual tape. Though simple at first glance, the technology’s potential impact is extraordinary, the researchers say.

The concept of superomniphobic surfaces isn’t new. Researchers have been studying superomniphobic coatings since about 2007, and currently superomniphobic coatings can be sprayed, deposited or etched onto any surface for a similar effect; however, it requires costly equipment, complex techniques, and must be done by an experienced professional.

By contrast, the Kota group’s superomniphobic tape can be used by anyone, making it a practical solution in a variety of civilian, commercial, and military applications including corrosion resistance, self cleaning, drag reduction, liquid waste minimization, and more.

The researchers feel that future challenges in this field are exciting ­- yet puzzling. While many applications of superomniphobic coatings have already been outlined, coming up with a superomniphobic coating that is mechanically durable remains a major challenge.

Kota has filed a patent and sees tape and adhesive manufacturers as well as the packing industry having a strong interest in the product. He and his group will continue to research the mechanical durability of their product.

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

Free-Standing, Flexible, Superomniphobic Films by Hamed Vahabi, Wei Wang, Sanli Movafaghi, and Arun K. Kota. ACS Appl. Mater. Interfaces, 2016, 8 (34), pp 21962–21967 DOI: 10.1021/acsami.6b06333 Publication Date (Web): August 19, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

Sand and nanotechnology

There’s some good news coming out of the University of California, Riverside regarding sand and lithium-ion (li-ion) batteries, which I will temper with some additional information later in this posting.

First, the good news is that researchers have a new non-toxic, low cost way to produce a component in lithium-ion (li-ion) batteries according to a July 8, 2014 news item on ScienceDaily,

Researchers at the University of California, Riverside’s Bourns College of Engineering have created a lithium ion battery that outperforms the current industry standard by three times. The key material: sand. Yes, sand.

“This is the holy grail — a low cost, non-toxic, environmentally friendly way to produce high performance lithium ion battery anodes,” said Zachary Favors, a graduate student working with Cengiz and Mihri Ozkan, both engineering professors at UC Riverside.

The idea came to Favors six months ago. He was relaxing on the beach after surfing in San Clemente, Calif. when he picked up some sand, took a close look at it and saw it was made up primarily of quartz, or silicon dioxide.

His research is centered on building better lithium ion batteries, primarily for personal electronics and electric vehicles. He is focused on the anode, or negative side of the battery. Graphite is the current standard material for the anode, but as electronics have become more powerful graphite’s ability to be improved has been virtually tapped out.

A July 8, 2014 University of California at Riverside news release by Sean Nealon, which originated the news item, describes some of the problems with silicon as a replacement for graphite and how the researchers approached those problems,

Researchers are now focused on using silicon at the nanoscale, or billionths of a meter, level as a replacement for graphite. The problem with nanoscale silicon is that it degrades quickly and is hard to produce in large quantities.

Favors set out to solve both these problems. He researched sand to find a spot in the United States where it is found with a high percentage of quartz. That took him to the Cedar Creek Reservoir, east of Dallas, where he grew up.

Sand in hand, he came back to the lab at UC Riverside and milled it down to the nanometer scale, followed by a series of purification steps changing its color from brown to bright white, similar in color and texture to powdered sugar.

After that, he ground salt and magnesium, both very common elements found dissolved in sea water into the purified quartz. The resulting powder was then heated. With the salt acting as a heat absorber, the magnesium worked to remove the oxygen from the quartz, resulting in pure silicon.

The Ozkan team was pleased with how the process went. And they also encountered an added positive surprise. The pure nano-silicon formed in a very porous 3-D silicon sponge like consistency. That porosity has proved to be the key to improving the performance of the batteries built with the nano-silicon.

Now, the Ozkan team is trying to produce larger quantities of the nano-silicon beach sand and is planning to move from coin-size batteries to pouch-size batteries that are used in cell phones.

The research is supported by Temiz Energy Technologies. The UCR Office of Technology Commercialization has filed patents for inventions reported in the research paper.

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

Scalable Synthesis of Nano-Silicon from Beach Sand for Long Cycle Life Li-ion Batteries by Zachary Favors, Wei Wang, Hamed Hosseini Bay, Zafer Mutlu, Kazi Ahmed, Chueh Liu, Mihrimah Ozkan, & Cengiz S. Ozkan. Scientific Reports 4, Article number: 5623 doi:10.1038/srep05623 Published 08 July 2014

While this is good news, it does pose a conundrum of sorts. It seems that supplies of sand are currently under siege. A documentary, Sand Wars (2013) lays out the issues (from the Sand Wars website’s Synopsis page),

Most of us think of it as a complimentary ingredient of any beach vacation. Yet those seemingly insignificant grains of silica surround our daily lives. Every house, skyscraper and glass building, every bridge, airport and sidewalk in our modern society depends on sand. We use it to manufacture optical fiber, cell phone components and computer chips. We find it in our toothpaste, powdered foods and even in our glass of wine (both the glass and the wine, as a fining agent)!

Is sand an infinite resource? Can the existing supply satisfy a gigantic demand fueled by construction booms?  What are the consequences of intensive beach sand mining for the environment and the neighboring populations?

Based on encounters with sand smugglers, barefoot millionaires, corrupt politicians, unscrupulous real estate developers and environmentalists, this investigation takes us around the globe to unveil a new gold rush and a disturbing fact: the “SAND WARS” have begun.

Dr. Muditha D Senarath Yapa of John Keells Research at John Keells Holdings comments on the situation in Sri Lanka in his June 22, 2014 article (Nanotechnology – Depleting the most precious minerals for a few dollars) for The Nation,

Many have written for many years about the mineral sands of Pulmoddai. It is a national tragedy that for more than 50 years, we have been depleting the most precious minerals of our land for a few dollars. There are articles that appeared in various newspapers on how the mineral sands industry has boomed over the years. I hope the readers understand that it only means that we are depleting our resources faster than ever. According to the Lanka Mineral Sands Limited website, 90,000 tonnes of ilmenite, 9,000 tonnes of rutile, 5,500 tonnes of zircon, 100 tonnes of monazite and 4,000 tonnes of high titanium ilmenite are produced annually and shipped away to other countries.

… It is time for Sri Lanka to look at our own resources with this new light and capture the future nano materials market to create value added materials.

It’s interesting that he starts with the depletion of the sands as a national tragedy and ends with a plea to shift from a resource-based economy to a manufacturing-based economy. (This plea resonates strongly here in Canada where we too are a resource-based economy.)

Sidebar: John Keells Holdings is a most unusual company, from the About Us page,

In terms of market capitalisation, John Keells Holdings PLC is one of the largest listed conglomerate on the Colombo Stock Exchange. Other measures tell a similar tale; our group companies manage the largest number of hotel rooms in Sri Lanka, own the country’s largest privately-owned transportation business and hold leading positions in Sri Lanka’s key industries: tea, food and beverage manufacture and distribution, logistics, real estate, banking and information technology. Our investment in Sri Lanka is so deep and widely diversified that our stock price is sometimes used by international financial analysts as a benchmark of the country’s economy.

Yapa heads the companies research effort, which recently celebrated a synthetic biology agreement (from a May 2014 John Keells news release by Nuwan),

John Keells Research Signs an Historic Agreement with the Human Genetics Unit, Faculty of Medicine, University of Colombo to establish Sri Lanka’s first Synthetic Biology Research Programme.

Getting back to sand, these three pieces, ‘sand is good for li-ion batteries’, ‘sand is a diminishing resource’, and ‘let’s stop being a source of sand for other countries’ lay bare some difficult questions about our collective future on this planet.

Charging portable electronics in 10 minutes (hopefully) with a 3D (silicon-decorated) carbon nanotube cluster

I sometimes think there’s a worldwide obsession with lithium-ion batteries as hardly a day passes without at least one story about them. To honour that obsession, here’s a June 11, 2014 news item on Azonano describing a new technique which could lead to a faster charging time for mobile electronics,

Researchers at the University of California, Riverside [UCR] Bourns College of Engineering have developed a three-dimensional, silicon-decorated, cone-shaped carbon-nanotube cluster architecture for lithium ion battery anodes that could enable charging of portable electronics in 10 minutes, instead of hours.

A June 10, 2014 UCR news release by Sean Nealon, which originated the news item, notes the ubiquity of lithium-ion batteries in modern electronics and explains why silicon was used in this research,

Lithium ion batteries are the rechargeable battery of choice for portable electronic devices and electric vehicles. But, they present problems. Batteries in electric vehicles are responsible for a significant portion of the vehicle mass. And the size of batteries in portable electronics limits the trend of down-sizing.

Silicon is a type of anode material that is receiving a lot of attention because its total charge capacity is 10 times higher than commercial graphite based lithium ion battery anodes. Consider a packaged battery full-cell. Replacing the commonly used graphite anode with silicon anodes will potentially result in a 63 percent increase of total cell capacity and a battery that is 40 percent lighter and smaller.

The news release then provides a very brief description of the technology,

…, UC Riverside researchers developed a novel structure of three-dimensional silicon decorated cone-shaped carbon nanotube clusters architecture via chemical vapor deposition and inductively coupled plasma treatment.

Lithium ion batteries based on this novel architecture demonstrate a high reversible capacity and excellent cycling stability. The architecture demonstrates excellent electrochemical stability and irreversibility even at high charge and discharge rates, nearly 16 times faster than conventionally used graphite based anodes.

The researchers believe the ultrafast rate of charge and discharge can be attributed to two reasons, said Wei Wang, lead author of the paper.

One, the seamless connection between graphene covered copper foil and carbon nanotubes enhances the active material-current collector contact integrity which facilitates charge and thermal transfer in the electrode system.

Two, the cone-shaped architecture offers small interpenetrating channels for faster electrolyte access into the electrode which may enhance the rate performance.

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

Silicon Decorated Cone Shaped Carbon Nanotube Clusters for Lithium Ion Battery Anodes by Wei Wang, Isaac Ruiz, Kazi Ahmed, Hamed Hosseini Bay, Aaron S. George, Johnny Wang, John Butler, Mihrimah Ozkan, and Cengiz S. Ozkan. Small DOI: 10.1002/smll.201400088 Article first published online: 19 APR 2014

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.