Tag Archives: Chenhui Zhu

Breakthrough for tissue-interfaced bioelectronics

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Let’s call this a cold open,

This October 24, 2024 news item on ScienceDaily describes some of what is in the video

The ideal material for interfacing electronics with living tissue is soft, stretchable, and just as water-loving as the tissue itself–in short, a hydrogel. Semiconductors, the key materials for bioelectronics such as pacemakers, biosensors, and drug delivery devices, on the other hand, are rigid, brittle, and water-hating, impossible to dissolve in the way hydrogels have traditionally been built. Scientists have now solved this challenge that has long stymied researchers, reimagining the process of creating hydrogels to build a powerful semiconductor in hydrogel form. The result is a bluish gel that flutters like a sea jelly in water but retains the immense semiconductive ability needed to transmit information between living tissue and machine.

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An October 24, 2024 University of Chicago news release (also on EurekAlert) by Paul Dailing, which originated the news item, describes the breakthrough, Note: Links have been removed,

A paper published today in Science from the UChicago Pritzker School of Molecular Engineering (PME) has solved this challenge that has long stymied researchers, reimagining the process of creating hydrogels to build a powerful semiconductor in hydrogel form. Led by Asst. Prof. Sihong Wang’s research group, the result is a bluish gel that flutters like a sea jelly in water but retains the immense semiconductive ability needed to transmit information between living tissue and machine.

The material demonstrated tissue-level moduli as soft as 81 kPa, stretchability of 150% strain, and charge-carrier mobility up to 1.4 cm2 V-1 s-1. This means their material—both semiconductor and hydrogel at the same time—ticks all the boxes for an ideal bioelectronic interface.

“When making implantable bioelectronic devices, one challenge you must address is to make a device with tissue-like mechanical properties,” said Yahao Dai, the first author of the new paper. “That way, when it gets directly interfaced with the tissue, they can deform together and also form a very intimate bio-interface.”

Although the paper mainly focused on the challenges facing implanted medical devices such as biochemical sensors and pacemakers, Dai said the material also has many potential non-surgical applications, like better readings off the skin or improved care for wounds.

“It has very soft mechanical properties and a large degree of hydration similar to living tissue,” said UChicago PME Asst. Prof. Sihong Wang. “Hydrogel is also very porous, so it allows the efficient diffusion transport of different kinds of nutrition and chemicals. All these traits combine to make hydrogel probably the most useful material for tissue engineering and drug delivery.”

‘Let’s change our perspective’

The typical way of making a hydrogel is to take a material, dissolve it in water, and add the gelation chemicals to puff the new liquid into a gel form. Some materials simply dissolve in water, others require researchers to tinker and chemically modify the process, but the core mechanism is the same: No water, no hydrogel.

Semiconductors, however, don’t normally dissolve in water. Rather than find new, time-consuming means of trying to force the process, the UChicago PME team re-examined the question.

“We started to think, ‘Okay, let’s change our perspective,’ and we came up with a solvent exchange process,” Dai said.

Instead of dissolving the semiconductors in water, they dissolved them in an organic solvent that is miscible with water. They then prepared a gel from the dissolved semiconductors and hydrogel precursors. Their gel initially was an organogel, not a hydrogel.

“To eventually turn it into a hydrogel, we then immersed the whole material system into the water to let the organic solvent dissolve out and let the water come in,” Dai said.

An important benefit of such a solvent-exchange-based method is its broad applicability to different types of polymer semiconductors with different functions.

‘One plus one is greater than two’

The hydrogel semiconductor, which the team has patented and is commercializing through UChicago’s Polsky Center for Entrepreneurship and Innovation, is not merging a semiconductor with a hydrogel. It’s one material that is both semiconductor and hydrogel at the same time.

“It’s just one piece that has both semiconducting properties and hydrogel design, meaning that this whole piece is just like any other hydrogel,” Wang said.

Unlike any other hydrogel, however, the new material actually improved biological functions in two areas, creating better results than either hydrogel or semiconductor could accomplish on their own.

First, having a very soft material bond directly with tissue reduces the immune responses and inflammation typically triggered when a medical device is implanted.

Second, because hydrogels are so porous, the new material enables elevated biosensing response and stronger photo-modulation effects. With biomolecules being able to diffuse into the film to have volumetric interactions, the interaction sites for biomarkers-under-detection are significantly increased, which gives rise to higher sensitivity. Besides sensing, the responses to light for therapeutic functions at tissue surfaces also get increased from the more efficient transport of redox-active species. This benefits functions such as light-operated pacemakers or wound dressing that can be more efficiently heated with a flick of light to help speed healing.

“It’s a ‘one plus one is greater than two’ kind of combination,” Wang joked.

Researchers in the lab of UChicago Pritzker School of Engineering Asst. Prof. Sihong Wang (right), including PhD student Yahao Dai (left), have developed a hydrogel that retains the semiconductive ability needed to transmit information between living tissue and machine, which can be used both in implantable medical devices and non-surgical applications. (Photo by John Zich)

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

Soft hydrogel semiconductors with augmented biointeractive functions by Yahao Dai, Shinya Wai, Pengju Li, Naisong Shan, Zhiqiang Cao, Yang Li, Yunfei Wang, Youdi Liu, Wei Liu, Kan Tang, Yuzi Liu, Muchuan Hua, Songsong Li, Nan Li, Shivani Chatterji, H. Christopher Fry, Sean Lee, Cheng Zhang, Max Weires, Sean Sutyak, Jiuyun Shi, Chenhui Zhu, Jie Xu, Xiaodan Gu, Bozhi Tian, and Sihong Wang. Science 24 Oct 2024 Vol 386, Issue 6720 pp. 431-439 DOI: 10.1126/science.adp9314

This paper is behind a paywall.

Jiggly jell-o as a new hydrogen fuel catalyst

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Jello [uploaded from https://www.organicauthority.com/eco-chic-table/new-jell-o-mold-jiggle-chic-holidays]

I’m quite intrigued by this ‘jell-o’ story. It’s hard to believe a childhood dessert might prove to have an application as a catalyst for producing hydrogen fuel. From a December 14, 2018 news item on Nanowerk,

A cheap and effective new catalyst developed by researchers at the University of California, Berkeley, can generate hydrogen fuel from water just as efficiently as platinum, currently the best — but also most expensive — water-splitting catalyst out there.

The catalyst, which is composed of nanometer-thin sheets of metal carbide, is manufactured using a self-assembly process that relies on a surprising ingredient: gelatin, the material that gives Jell-O its jiggle.

Two-dimensional metal carbides spark a reaction that splits water into oxygen and valuable hydrogen gas. Berkeley researchers have discovered an easy new recipe for cooking up these nanometer-thin sheets that is nearly as simple as making Jell-O from a box. (Xining Zang graphic, copyright Wiley)

A December 13, 2018 University of California at Berkeley (UC Berkeley) news release by Kara Manke (also on EurekAlert but published on Dec. 14, 2018), which originated the news item, provides more technical detail,

“Platinum is expensive, so it would be desirable to find other alternative materials to replace it,” said senior author Liwei Lin, professor of mechanical engineering at UC Berkeley. “We are actually using something similar to the Jell-O that you can eat as the foundation, and mixing it with some of the abundant earth elements to create an inexpensive new material for important catalytic reactions.”

The work appears in the Dec. 13 [2018] print edition of the journal Advanced Materials.

A zap of electricity can break apart the strong bonds that tie water molecules together, creating oxygen and hydrogen gas, the latter of which is an extremely valuable source of energy for powering hydrogen fuel cells. Hydrogen gas can also be used to help store energy from renewable yet intermittent energy sources like solar and wind power, which produce excess electricity when the sun shines or when the wind blows, but which go dormant on rainy or calm days.

A black and white image of metal carbide under high magnification.

When magnified, the two-dimensional metal carbides resemble sheets of cell[o]phane. (Xining Zang photo, copyright Wiley)

But simply sticking an electrode in a glass of water is an extremely inefficient method of generating hydrogen gas. For the past 20 years, scientists have been searching for catalysts that can speed up this reaction, making it practical for large-scale use.

“The traditional way of using water gas to generate hydrogen still dominates in industry. However, this method produces carbon dioxide as byproduct,” said first author Xining Zang, who conducted the research as a graduate student in mechanical engineering at UC Berkeley. “Electrocatalytic hydrogen generation is growing in the past decade, following the global demand to lower emissions. Developing a highly efficient and low-cost catalyst for electrohydrolysis will bring profound technical, economical and societal benefit.”

To create the catalyst, the researchers followed a recipe nearly as simple as making Jell-O from a box. They mixed gelatin and a metal ion — either molybdenum, tungsten or cobalt — with water, and then let the mixture dry.

“We believe that as gelatin dries, it self-assembles layer by layer,” Lin said. “The metal ion is carried by the gelatin, so when the gelatin self-assembles, your metal ion is also arranged into these flat layers, and these flat sheets are what give Jell-O its characteristic mirror-like surface.”

Heating the mixture to 600 degrees Celsius triggers the metal ion to react with the carbon atoms in the gelatin, forming large, nanometer-thin sheets of metal carbide. The unreacted gelatin burns away.

The researchers tested the efficiency of the catalysts by placing them in water and running an electric current through them. When stacked up against each other, molybdenum carbide split water the most efficiently, followed by tungsten carbide and then cobalt carbide, which didn’t form thin layers as well as the other two. Mixing molybdenum ions with a small amount of cobalt boosted the performance even more.

“It is possible that other forms of carbide may provide even better performance,” Lin said.

On the left, an illustration of blue spheres, representing gelatin molecules, arranged in a lattice shape. On the right, an illustration of thin sheets of metal carbide.

Molecules in gelatin naturally self-assemble in flat sheets, carrying the metal ions with them (left). Heating the mixture to 600 degrees Celsius burns off the gelatin, leaving nanometer-thin sheets of metal carbide. (Xining Zang illustration, copyright Wiley)

The two-dimensional shape of the catalyst is one of the reasons why it is so successful. That is because the water has to be in contact with the surface of the catalyst in order to do its job, and the large surface area of the sheets mean that the metal carbides are extremely efficient for their weight.

Because the recipe is so simple, it could easily be scaled up to produce large quantities of the catalyst, the researchers say.

“We found that the performance is very close to the best catalyst made of platinum and carbon, which is the gold standard in this area,” Lin said. “This means that we can replace the very expensive platinum with our material, which is made in a very scalable manufacturing process.”

Co-authors on the study are Lujie Yang, Buxuan Li and Minsong Wei of UC Berkeley, J. Nathan Hohman and Chenhui Zhu of Lawrence Berkeley National Lab; Wenshu Chen and Jiajun Gu of Shanghai Jiao Tong University; Xiaolong Zou and Jiaming Liang of the Shenzhen Institute; and Mohan Sanghasadasa of the U.S. Army RDECOM AMRDEC.

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

Self‐Assembly of Large‐Area 2D Polycrystalline Transition Metal Carbides for Hydrogen Electrocatalysis by Xining Zang, Wenshu Chen, Xiaolong Zou, J. Nathan Hohman, Lujie Yang
Buxuan Li, Minsong Wei, Chenhui Zhu, Jiaming Liang, Mohan Sanghadasa, Jiajun Gu, Liwei Lin. Advanced Materials Volume30, Issue 50 December 13, 2018 1805188 DOI: https://doi.org/10.1002/adma.201805188 First published [online]: 09 October 2018

This paper is behind a paywall.

Weaving at the nanoscale

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A Jan. 21, 2016 news item on ScienceDaily announces a brand new technique,

For the first time, scientists have been able to weave a material at molecular level. The research is led by University of California Berkeley, in cooperation with Stockholm University. …

A Jan. 21, 2016 Stockholm University press release, which originated the news item, provides more information,

Weaving is a well-known way of making fabric, but has until now never been used at the molecular level. Scientists have now been able to weave organic threads into a three-dimensional material, using copper as a template. The new material is a COF, covalent organic framework, and is named COF-505. The copper ions can be removed and added without changing the underlying structure, and at the same time the elasticity can be reversibly changed.

– It almost looks like a molecular version of the Vikings chain-armour. The material is very flexible, says Peter Oleynikov, researcher at the Department of Materials and Environmental Chemistry at Stockholm University.

COF’s are like MOF’s porous three-dimensional crystals with a very large internal surface that can adsorb and store enormous quantities of molecules. A potential application is capture and storage of carbon dioxide, or using COF’s as a catalyst to make useful molecules from carbon dioxide.

Complex structure determined in Stockholm

The research is led by Professor Omar Yaghi at University of California Berkeley. At Stockholm University Professor Osamu Terasaki, PhD Student Yanhang Ma and Researcher Peter Oleynikov have contributed to determine the structure of COF-505 at atomic level from a nano-crystal, using electron crystallography methods.

– It is a difficult, complicated structure and it was very demanding to resolve. We’ve spent lot of time and efforts on the structure solution. Now we know exactly where the copper is and we can also replace the metal. This opens up many possibilities to make other materials, says Yanhang Ma, PhD Student at the Department of Materials and Environmental Chemistry at Stockholm University.

Another of the collaborating institutions, US Department of Energy Lawrence Berkeley National Laboratory issued a Jan. 21, 2016 news release on EurekAlert, providing a different perspective and some additional details,

There are many different ways to make nanomaterials but weaving, the oldest and most enduring method of making fabrics, has not been one of them – until now. An international collaboration led by scientists at the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley, has woven the first three-dimensional covalent organic frameworks (COFs) from helical organic threads. The woven COFs display significant advantages in structural flexibility, resiliency and reversibility over previous COFs – materials that are highly prized for their potential to capture and store carbon dioxide then convert it into valuable chemical products.

…

“Weaving in chemistry has been long sought after and is unknown in biology,” Yaghi says [Omar Yaghi, chemist who holds joint appointments with Berkeley Lab’s Materials Sciences Division and UC Berkeley’s Chemistry Department and is the co-director of the Kavli Energy NanoScience Institute {Kavli-ENSI}]. “However, we have found a way of weaving organic threads that enables us to design and make complex two- and three-dimensional organic extended structures.”

…

COFs and their cousin materials, metal organic frameworks (MOFs), are porous three-dimensional crystals with extraordinarily large internal surface areas that can absorb and store enormous quantities of targeted molecules. Invented by Yaghi, COFs and MOFs consist of molecules (organics for COFs and metal-organics for MOFs) that are stitched into large and extended netlike frameworks whose structures are held together by strong chemical bonds. Such frameworks show great promise for, among other applications, carbon sequestration.

Through another technique developed by Yaghi, called “reticular chemistry,” these frameworks can also be embedded with catalysts to carry out desired functions: for example, reducing carbon dioxide into carbon monoxide, which serves as a primary building block for a wide range of chemical products including fuels, pharmaceuticals and plastics.

In this latest study, Yaghi and his collaborators used a copper(I) complex as a template for bringing threads of the organic compound “phenanthroline” into a woven pattern to produce an immine-based framework they dubbed COF-505. Through X-ray and electron diffraction characterizations, the researchers discovered that the copper(I) ions can be reversibly removed or restored to COF-505 without changing its woven structure. Demetalation of the COF resulted in a tenfold increase in its elasticity and remetalation restored the COF to its original stiffness.

“That our system can switch between two states of elasticity reversibly by a simple operation, the first such demonstration in an extended chemical structure, means that cycling between these states can be done repeatedly without degrading or altering the structure,” Yaghi says. “Based on these results, it is easy to imagine the creation of molecular cloths that combine unusual resiliency, strength, flexibility and chemical variability in one material.”

Yaghi says that MOFs can also be woven as can all structures based on netlike frameworks. In addition, these woven structures can also be made as nanoparticles or polymers, which means they can be fabricated into thin films and electronic devices.

“Our weaving technique allows long threads of covalently linked molecules to cross at regular intervals,” Yaghi says. “These crossings serve as points of registry, so that the threads have many degrees of freedom to move away from and back to such points without collapsing the overall structure, a boon to making materials with exceptional mechanical properties and dynamics.”

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This research was primarily supported by BASF (Germany) and King Abdulaziz City for Science and Technology (KACST).

It’s unusual that neither Stockholm University not the Lawrence Berkeley National Laboratory list all of the institutions involved. To get a sense of this international collaboration’s size, I’m going to list them,

  • 1Department of Chemistry, University of California, Berkeley, Materials Sciences Division, Lawrence Berkeley National Laboratory, and Kavli Energy NanoSciences Institute, Berkeley, CA 94720, USA.
  • 2Department of Materials and Environmental Chemistry, Stockholm University, SE-10691 Stockholm, Sweden.
  • 3Department of New Architectures in Materials Chemistry, Materials Science Institute of Madrid, Consejo Superior de Investigaciones Científicas, Madrid 28049, Spain.
  • 4Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8565, Japan.
  • 5NSF Nanoscale Science and Engineering Center (NSEC), University of California at Berkeley, 3112 Etcheverry Hall, Berkeley, CA 94720, USA.
  • 6Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
  • 7King Abdulaziz City of Science and Technology, Post Office Box 6086, Riyadh 11442, Saudi Arabia.
  • 8Material Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
  • 9School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China.

Given that some of the money came from a German company, I’m surprised not one German institution was involved.

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

Weaving of organic threads into a crystalline covalent organic framework by Yuzhong Liu, Yanhang Ma, Yingbo Zhao, Xixi Sun, Felipe Gándara, Hiroyasu Furukawa, Zheng Liu, Hanyu Zhu, Chenhui Zhu, Kazutomo Suenaga, Peter Oleynikov, Ahmad S. Alshammari, Xiang Zhang, Osamu Terasaki, Omar M. Yaghi. Science  22 Jan 2016: Vol. 351, Issue 6271, pp. 365-369 DOI: 10.1126/science.aad4011

This paper is behind a paywall.