Tag Archives: Yang Yang

Stretching diamonds to improve electronic devices

On the last day of 2020, City University of Hong Kong (CityU) announced a technique for stretching diamonds that could result in a new generation of electronic devices. A December 31, 2020 news item on ScienceDaily makes the announcement,

Diamond is the hardest material in nature. It also has great potential as an excellent electronic material. A research team has demonstrated for the first time the large, uniform tensile elastic straining of microfabricated diamond arrays through the nanomechanical approach. Their findings have shown the potential of strained diamonds as prime candidates for advanced functional devices in microelectronics, photonics, and quantum information technologies.

A December 31, 2020 CityU press release on EurekAlert , which originated the news item, delves further into the research,

The research was co-led by Dr Lu Yang, Associate Professor in the Department of Mechanical Engineering (MNE) at CityU and researchers from Massachusetts Institute of Technology (MIT) and Harbin Institute of Technology (HIT). Their findings have been recently published in the prestigious scientific journal Science, titled “Achieving large uniform tensile elasticity in microfabricated diamond“.

“This is the first time showing the extremely large, uniform elasticity of diamond by tensile experiments. Our findings demonstrate the possibility of developing electronic devices through ‘deep elastic strain engineering’ of microfabricated diamond structures,” said Dr Lu.

Diamond: “Mount Everest” of electronic materials

Well known for its hardness, industrial applications of diamonds are usually cutting, drilling, or grinding. But diamond is also considered as a high-performance electronic and photonic material due to its ultra-high thermal conductivity, exceptional electric charge carrier mobility, high breakdown strength and ultra-wide bandgap. Bandgap is a key property in semi-conductor, and wide bandgap allows operation of high-power or high-frequency devices. “That’s why diamond can be considered as ‘Mount Everest’ of electronic materials, possessing all these excellent properties,” Dr Lu said.

However, the large bandgap and tight crystal structure of diamond make it difficult to “dope”, a common way to modulate the semi-conductors’ electronic properties during production, hence hampering the diamond’s industrial application in electronic and optoelectronic devices. A potential alternative is by “strain engineering”, that is to apply very large lattice strain, to change the electronic band structure and associated functional properties. But it was considered as “impossible” for diamond due to its extremely high hardness.

Then in 2018, Dr Lu and his collaborators discovered that, surprisingly, nanoscale diamond can be elastically bent with unexpected large local strain. This discovery suggests the change of physical properties in diamond through elastic strain engineering can be possible. Based on this, the latest study showed how this phenomenon can be utilized for developing functional diamond devices.

Uniform tensile straining across the sample

The team firstly microfabricated single-crystalline diamond samples from a solid diamond single crystals. The samples were in bridge-like shape – about one micrometre long and 300 nanometres wide, with both ends wider for gripping (See image: Tensile straining of diamond bridges). The diamond bridges were then uniaxially stretched in a well-controlled manner within an electron microscope. Under cycles of continuous and controllable loading-unloading of quantitative tensile tests, the diamond bridges demonstrated a highly uniform, large elastic deformation of about 7.5% strain across the whole gauge section of the specimen, rather than deforming at a localized area in bending. And they recovered their original shape after unloading.

By further optimizing the sample geometry using the American Society for Testing and Materials (ASTM) standard, they achieved a maximum uniform tensile strain of up to 9.7%, which even surpassed the maximum local value in the 2018 study, and was close to the theoretical elastic limit of diamond. More importantly, to demonstrate the strained diamond device concept, the team also realized elastic straining of microfabricated diamond arrays.

Tuning the bandgap by elastic strains

The team then performed density functional theory (DFT) calculations to estimate the impact of elastic straining from 0 to 12% on the diamond’s electronic properties. The simulation results indicated that the bandgap of diamond generally decreased as the tensile strain increased, with the largest bandgap reduction rate down from about 5 eV to 3 eV at around 9% strain along a specific crystalline orientation. The team performed an electron energy-loss spectroscopy analysis on a pre-strained diamond sample and verified this bandgap decreasing trend.

Their calculation results also showed that, interestingly, the bandgap could change from indirect to direct with the tensile strains larger than 9% along another crystalline orientation. Direct bandgap in semi-conductor means an electron can directly emit a photon, allowing many optoelectronic applications with higher efficiency.

These findings are an early step in achieving deep elastic strain engineering of microfabricated diamonds. By nanomechanical approach, the team demonstrated that the diamond’s band structure can be changed, and more importantly, these changes can be continuous and reversible, allowing different applications, from micro/nanoelectromechanical systems (MEMS/NEMS), strain-engineered transistors, to novel optoelectronic and quantum technologies. “I believe a new era for diamond is ahead of us,” said Dr Lu.

Here’s an illustration provided by the researchers,

Caption: Stretching of microfabricated diamonds pave ways for applications in next-generation microelectronics.. Credit: Dang Chaoqun / City University of Hong Kong

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

Achieving large uniform tensile elasticity in microfabricated diamond by Chaoqun Dang, Jyh-Pin Chou, Bing Dai, Chang-Ti Chou, Yang Yang, Rong Fan, Weitong Lin, Fanling Meng, Alice Hu, Jiaqi Zhu, Jiecai Han, Andrew M. Minor, Ju Li, Yang Lu. Science 01 Jan 2021: Vol. 371, Issue 6524, pp. 76-78 DOI: 10.1126/science.abc4174

This paper is behind a paywall.

Improving batteries with cellulosic nanomaterials

This is a cellulose nanocrystal (CNC) story and in this story it’s derived from trees as opposed to banana skins or carrots or … A February 19, 2020 news item on Nanowerk announces CNC research from Northeastern University (Massachusetts, US),

Nature isn’t always generous with its secrets. That’s why some researchers look into unusual places for solutions to our toughest challenges, from powerful antibiotics hiding in the guts of tiny worms, to swift robots inspired by bats.

Now, Northeastern researchers have taken to the trees to look for ways to make new sustainable materials from abundant natural resources—specifically, within the chemical structure of microfibers that make up wood.

A team led by Hongli (Julie) Zhu, an assistant professor of mechanical and industrial engineering at Northeastern, is using unique nanomaterials derived from cellulose to improve the large and expensive kind of batteries needed to store renewable energy harnessed from sources such as sunlight and the wind.

A February 18, 2020 Northeastern University news release by Roberto Molar Candanosa, which originated the news item, provides more detail (Note: Links have been removed),

Cellulose, the most abundant natural polymer on Earth, is also the most important structural component of plants. It contains important molecular structures to improve batteries, reduce plastic pollution, and power the sort of electrical grids that could support entire communities with renewable energy, Zhu says.  

“We try to use polymers from wood, from bark, from seeds, from flowers, bacteria, green tea—from these kinds of plants to replace plastic,”  Zhu says.

One of the main challenges in storing energy from the sun, wind, and other types of renewables is that variation in factors such as the weather lead to inconsistent sources of power. 

That’s where batteries with large capacity come in. But storing the large amounts of energy that sunlight and the wind are able to provide requires a special kind of device.

The most advanced batteries to do that are called flow batteries, and are made with vanadium ions dissolved in acid in two separate tanks—one with a substance of negatively charged ions, and one with positive ones. The two solutions are continuously pumped from the tank into a cell, which functions like an engine for the battery. 

These substances are always separated by a special membrane that ensures that they exchange positive hydrogen ions without flowing into each other. That selective exchange of ions is the basis for the ability of the battery to charge and discharge energy. 

Flow batteries are ideal devices in which to store solar and wind energy because they can be tweaked to increase the amount of energy stored without compromising the amount of energy that can be generated. The bigger the tanks, the more energy the battery can store from non-polluting and practically inexhaustible resources.

But manufacturing them requires several moving pieces of hardware. As the membrane separating the two flowing substances decays, it can cause the vanadium ions from the solution to mix. That crossover reduces the stability of a battery, along with its capacity to store energy.

Zhu says the limited efficiency of that membrane, combined with  its high cost, are the main factors keeping flow batteries from being widely used in large-scale grids.

In a recent paper, Zhu reported that a new membrane made with cellulose nanocrystals demonstrates superior efficiency compared to other membranes used commonly in the market. The team tested different membranes made from cellulose nanocrystals to make flow batteries cheaper.

“The cost of our membrane per square meter is 147.68 US dollars, ” Zhu says, adding that her calculations do not include costs associated with marketing. “The price quote for the commercialized Nafion membrane is $1,321 per square meter.”

Their tests also showed that the membranes, made with support from the Rogers Corporation and its Innovation Center at Northeastern’s Kostas Research Institute, can offer substantially longer battery lifetimes than other membranes. 

Zhu’s naturally derived membrane is especially efficient because its cellular structure contains thousands of hydroxyl groups, which involve bonds of hydrogen and oxygen that make it easy for water to be transported in plants and trees. 

In flow batteries, that molecular makeup speeds the transport of protons as they flow through the membrane.

The membrane also consists of another polymer known as poly(vinylidene fluoride-hexafluoropropylene), which prevents the negatively and positively charged acids from mixing with each other. 

“For these materials, one of the challenges is that it is difficult to find a polymer that is proton conductive and that is also a material that is very stable in the flowing acid,” Zhu says. 

Because these materials are practically everywhere, membranes made with it can be easily put together at large scales needed for complex power grids. 

Unlike other expensive artificial materials that need to be concocted in a lab, cellulose can be extracted from natural sources including algae, solid waste, and bacteria. 

“A lot of material in nature is a composite, and if we disintegrate its components, we can use it to extract cellulose,” Zhu says. “Like waste from our yard, and a lot of solid waste that we don’t always know what to do with.” 

Here’s a link to and a citation for the paper mentioned in the news release,

Stable and Highly Ion-Selective Membrane Made from Cellulose Nanocrystals for Aqueous Redox Flow Batteries by Alolika Mukhopadhyay, Zheng Cheng, Avi Natan, Yi Ma, Yang Yang, Daxian Cao, Wei Wan, Hongli Zhu. Nano Lett. 2019, 19, 12, 8979-8989 DOI: https://doi.org/10.1021/acs.nanolett.9b03964Publication Date:November 8, 2019 Copyright © 2019 American Chemical Society

This paper is behind a paywall.

Temporary tattoos mark the spot for surgery

Presumably they used markers of some kind before deciding on tattoos to mark the spot for surgeons.  Here’s more on the latest about temporary tattoos from a Dec. 21, 2016 news item on phys.org,

Tattoos aren’t just for body art. They can have medical applications, too. Doctors are using them on patients to mark an area for future treatment—particularly for non-melanoma skin cancer such as basal cell carcinoma—but the inks can cause problems. Now scientists have developed a better solution. In the journal ACS Nano, they report a new ink that glows only under certain light conditions and can disappear altogether after a period of time.

A Dec.21, 2016 American Chemical Society news release (also on EurekAlert), which originated the news item, describes the research and the reason for it in more detail,

Patients diagnosed with skin cancer typically have to wait up to three months between a biopsy confirming their condition and treatment. Doctors can mark the spot for possible future treatment using carbon graphite, India ink or fluorescent dye. But these pigments permanently color the skin, and can require laser or surgical removal after a patient has undergone surgery. They can also cause inflammation and discomfort at the site of the tattoo. Kai Chen, Gary S. Chuang, Hsian-Rong Tseng and colleagues wanted to develop a safer, more patient-friendly option.

The researchers created a time-limited pigment by cross-linking fluorescent supramolecular nanoparticles. Under ambient lighting, the nanoparticles are invisible, which would avoid unwanted markings in a patient’s skin. But the pigment glows under light shining at a wavelength of 465 nanometers, so doctors would be able to use a special light to see the dye. Testing in mice showed that tattoos created with these nanoparticles didn’t cause inflammation and lasted for three months. This would be long enough to mark a spot from biopsy through treatment for a non-melanoma patient.

The researchers have provided an image illustrating their work,

Temporary tattoo. Courtesy: ACS Nano

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

Cross-Linked Fluorescent Supramolecular Nanoparticles as Finite Tattoo Pigments with Controllable Intradermal Retention Times by Jin-sil Choi, Yazhen Zhu, Hongsheng Li, Parham Peyda, Thuy Tien Nguyen, Mo Yuan Shen, Yang Michael Yang, Jingyi Zhu, Mei Liu, Mandy M. Lee, Shih-Sheng Sun, Yang Yang, Hsiao-hua Yu, Kai Chen, Gary S. Chuang, and Hsian-Rong Tseng. ACS Nano, Article ASAP DOI: 10.1021/acsnano.6b06200 Publication Date (Web): November 30, 2016.

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

Parvus Therapeutics (Calgary, Canada) and reprogramming immune cells

An international collaboration of Canadian, Spanish, and US scientists has announced a new therapeutic approach which could reverse autoimmune diseases in a Feb. 17, 2016 news item on Nanotechnology Now,

• Nanotechnology Approach Restores Glucose Regulation and Motor Function in In Vivo Preclinical Models of Diabetes and Multiple Sclerosis, Respectively; Joint Swelling and Destruction Resolved in In Vivo Model of Rheumatoid Arthritis
• Parvus’ Approach Can Be Tailored to Treat Diverse Diseases

A Feb. 17, 2016 Parvus Therapeutics news release (also on EurekAlert), which originated the news item, provides more detail and a strong orientation to marketing communication,

Parvus Therapeutics today announced the publication in Nature of a seminal paper describing the discovery and applications of a novel therapeutic approach employing nanomedicines, referred to as “Navacims”TM, to reprogram white blood cells to become regulatory cells capable of blunting autoimmune responses and restoring the equilibrium of the immune system. Navacims are nanoparticles (NPs) coated with disease-relevant peptide-major histocompatibility complexes (pMHCs) that alter the behavior of pathogenic T lymphocytes by binding directly to their antigen receptors. The peer-reviewed article, titled “Expanding antigen-specific regulatory networks to treat autoimmunity” reports on a body of work, including results in multiple in vivo disease models, built on more than eight years of research by Parvus Founder and Chief Scientific Officer, Pere Santamaria, M.D., Ph.D.

Dr. Santamaria commented, “Autoimmune diseases, including type 1 diabetes, multiple sclerosis, and rheumatoid arthritis, are extraordinarily complex responses of our immune system against some of our own tissues (e.g. pancreas, brain and joints, respectively), leading to chronic organ inflammation, organ dysfunction, and, in some cases, premature death. Blunting these incompletely understood immune responses without suppressing the normal components of our immune system that protect us against infection and cancer is not currently possible.”

“However, our work offers a pharmaceutical solution to this fundamental problem,” Dr. Santamaria continued. “Navacims essentially re-program disease-causing white blood cells to become disease-suppressing cells, known as regulatory cells, leading to sustained therapeutic effects in various spontaneous and experimental autoimmune diseases, as reported in our article in Nature. Essentially, we have found that Navacims can be tailored to treat a wide range of autoimmune diseases, while sharing a common structure. Importantly, they have been shown to affect human white blood cells in the same manner as they do murine cells. Furthermore, Navacims have shown promising safety findings in preclinical in vivo models. Based on our results to date, we believe Navacims represent a therapeutic platform with broad-ranging health care implications.”

Findings being reported in Nature include:

pMHC class II Navacims expanded cognate CD4+ T-cells that consistently have a TR1-like, regulatory T cell surface phenotype, transcriptional pattern and cytokine profile (mouse=human TR1 cells) systemically.

pMHC class II-Navacims designed to target T cells in newly diabetic nonobese (NOD) mice restored normoglycemia (normal blood sugar regulation) in the majority of the mice tested.

Tailored pMHC class II Navacims restored motor function to paralyzed C57BL/6 mice at the peak of Experimental Autoimmune Encephalomyelitis (a model of Multiple Sclerosis).

pMHC class II Navacims, targeting disease-causing T cells in joints, resolved joint swelling and destruction in arthritic mice.

“The findings being reported in Nature represent a scientific advance for Parvus and also a major achievement in the field of Immunology,” said Janice M. LeCocq, CEO of Parvus. “We believe that Dr. Santamaria’s work has the potential to transform the treatment of many of the more than 80 major autoimmune diseases affecting humankind, alleviating the suffering of millions of patients and their families. Over the coming year, we will be dedicating much of our in-house efforts to the advancement of our two lead programs for type 1 diabetes and multiple sclerosis.”

“Dr. Santamaria’s work to target the immune system dysfunction that causes type 1 diabetes represents the kind of innovative work that JDRF believes will eventually get us to a cure for this disease,” said Juvenile Diabetes Research Foundation Vice President of Discovery Research Julia Greenstein, Ph.D. “He and his colleagues have made exciting progress towards possibly developing a new class of drugs that could rebalance certain T-cells and ultimately provide a cure for type 1 diabetes and other autoimmune diseases as well.” The JDRF has funded the work of Dr. Santamaria and his colleagues at Parvus to explore Navacim-based treatments for diabetes.

Parvus’ strategy is to establish partnerships with major pharmaceutical companies to undertake the clinical and commercial development of many of its product pipeline candidates while also reserving rights to others suitable for its own development and commercialization. Parvus currently is engaged in late stage discussions with multiple pharmaceutical companies with regard to the type 1 diabetes (T1D) program. Manufacturing scale-up is now underway to supply upcoming preclinical and clinical studies.

The work being reported in Nature was led by Dr. Pere Santamaria and largely executed at the University of Calgary, Cumming School of Medicine (animal models of disease) and the Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS) (humanized mouse work), with significant contributions from investigators at Institutions in Europe and the US. Further, Innovate Calgary, the technology-transfer and business-incubation center for the University of Calgary, provided early support for the transfer of the Navacims technology to and incubation of Parvus Therapeutics, which was organized as a separate entity in 2012.

It should be noted that this intervention has been tested on ‘humanized’ mice and, at this point, there don’t seem to have been any human clinical trials. At a guess I’d say we’re still several years away from this therapeutic intervention reaching the market, should it prove to be successful in humans.

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

Expanding antigen-specific regulatory networks to treat autoimmunity by Xavier Clemente Casares, Jesus Blanco, Poornima Ambalavanan, Jun Yamanouchi, Santiswarup Singha, Cesar Fandos, Sue Tsai, Jinguo Wang, Nahir Garabatos, Cristina Izquierdo, Smriti Agrawal, Michael B. Keough, V. Wee Yong, Eddie James, Anna Moore, Yang Yang, Thomas Stratmann, Pau Serra, & Pere Santamaria. Nature (2016) doi:10.1038/nature16962 Published online 17 February 2016

This paper is behind a paywall.

Better RRAM memory devices in the short term

Given my recent spate of posts about computing and the future of the chip (list to follow at the end of this post), this Rice University [Texas, US] research suggests that some improvements to current memory devices might be coming to the market in the near future. From a July 12, 2014 news item on Azonano,

Rice University’s breakthrough silicon oxide technology for high-density, next-generation computer memory is one step closer to mass production, thanks to a refinement that will allow manufacturers to fabricate devices at room temperature with conventional production methods.

A July 10, 2014 Rice University news release, which originated the news item, provides more detail,

Tour and colleagues began work on their breakthrough RRAM technology more than five years ago. The basic concept behind resistive memory devices is the insertion of a dielectric material — one that won’t normally conduct electricity — between two wires. When a sufficiently high voltage is applied across the wires, a narrow conduction path can be formed through the dielectric material.

The presence or absence of these conduction pathways can be used to represent the binary 1s and 0s of digital data. Research with a number of dielectric materials over the past decade has shown that such conduction pathways can be formed, broken and reformed thousands of times, which means RRAM can be used as the basis of rewritable random-access memory.

RRAM is under development worldwide and expected to supplant flash memory technology in the marketplace within a few years because it is faster than flash and can pack far more information into less space. For example, manufacturers have announced plans for RRAM prototype chips that will be capable of storing about one terabyte of data on a device the size of a postage stamp — more than 50 times the data density of current flash memory technology.

The key ingredient of Rice’s RRAM is its dielectric component, silicon oxide. Silicon is the most abundant element on Earth and the basic ingredient in conventional microchips. Microelectronics fabrication technologies based on silicon are widespread and easily understood, but until the 2010 discovery of conductive filament pathways in silicon oxide in Tour’s lab, the material wasn’t considered an option for RRAM.

Since then, Tour’s team has raced to further develop its RRAM and even used it for exotic new devices like transparent flexible memory chips. At the same time, the researchers also conducted countless tests to compare the performance of silicon oxide memories with competing dielectric RRAM technologies.

“Our technology is the only one that satisfies every market requirement, both from a production and a performance standpoint, for nonvolatile memory,” Tour said. “It can be manufactured at room temperature, has an extremely low forming voltage, high on-off ratio, low power consumption, nine-bit capacity per cell, exceptional switching speeds and excellent cycling endurance.”

In the latest study, a team headed by lead author and Rice postdoctoral researcher Gunuk Wang showed that using a porous version of silicon oxide could dramatically improve Rice’s RRAM in several ways. First, the porous material reduced the forming voltage — the power needed to form conduction pathways — to less than two volts, a 13-fold improvement over the team’s previous best and a number that stacks up against competing RRAM technologies. In addition, the porous silicon oxide also allowed Tour’s team to eliminate the need for a “device edge structure.”

“That means we can take a sheet of porous silicon oxide and just drop down electrodes without having to fabricate edges,” Tour said. “When we made our initial announcement about silicon oxide in 2010, one of the first questions I got from industry was whether we could do this without fabricating edges. At the time we could not, but the change to porous silicon oxide finally allows us to do that.”

Wang said, “We also demonstrated that the porous silicon oxide material increased the endurance cycles more than 100 times as compared with previous nonporous silicon oxide memories. Finally, the porous silicon oxide material has a capacity of up to nine bits per cell that is highest number among oxide-based memories, and the multiple capacity is unaffected by high temperatures.”

Tour said the latest developments with porous silicon oxide — reduced forming voltage, elimination of need for edge fabrication, excellent endurance cycling and multi-bit capacity — are extremely appealing to memory companies.

“This is a major accomplishment, and we’ve already been approached by companies interested in licensing this new technology,” he said.

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

Nanoporous Silicon Oxide Memory by Gunuk Wang, Yang Yang, Jae-Hwang Lee, Vera Abramova, Huilong Fei, Gedeng Ruan, Edwin L. Thomas, and James M. Tour. Nano Lett., Article ASAP DOI: 10.1021/nl501803s Publication Date (Web): July 3, 2014

Copyright © 2014 American Chemical Society

This paper is behind a paywall.

As for my recent spate of posts on computers and chips, there’s a July 11, 2014 posting about IBM, a 7nm chip, and much more; a July 9, 2014 posting about Intel and its 14nm low-power chip processing and plans for a 10nm chip; and, finally, a June 26, 2014 posting about HP Labs and its plans for memristive-based computing and their project dubbed ‘The Machine’.