(Press-News.org) MADISON - Portable electronics - typically made of non-renewable, non-biodegradable and potentially toxic materials - are discarded at an alarming rate in consumers' pursuit of the next best electronic gadget.
In an effort to alleviate the environmental burden of electronic devices, a team of University of Wisconsin-Madison researchers has collaborated with researchers in the Madison-based U.S. Department of Agriculture Forest Products Laboratory (FPL) to develop a surprising solution: a semiconductor chip made almost entirely of wood.
The research team, led by UW-Madison electrical and computer engineering professor Zhenqiang "Jack" Ma, described the new device in a paper published today (May 26, 2015) by the journal Nature Communications. The paper demonstrates the feasibility of replacing the substrate, or support layer, of a computer chip, with cellulose nanofibril (CNF), a flexible, biodegradable material made from wood.
"The majority of material in a chip is support. We only use less than a couple of micrometers for everything else," Ma says. "Now the chips are so safe you can put them in the forest and fungus will degrade it. They become as safe as fertilizer."
Zhiyong Cai, project leader for an engineering composite science research group at FPL, has been developing sustainable nanomaterials since 2009.
"If you take a big tree and cut it down to the individual fiber, the most common product is paper. The dimension of the fiber is in the micron stage," Cai says. "But what if we could break it down further to the nano scale? At that scale you can make this material, very strong and transparent CNF paper."
Working with Shaoqin "Sarah" Gong, a UW-Madison professor of biomedical engineering, Cai's group addressed two key barriers to using wood-derived materials in an electronics setting: surface smoothness and thermal expansion.
"You don't want it to expand or shrink too much. Wood is a natural hydroscopic material and could attract moisture from the air and expand," Cai says. "With an epoxy coating on the surface of the CNF, we solved both the surface smoothness and the moisture barrier."
Gong and her students also have been studying bio-based polymers for more than a decade. CNF offers many benefits over current chip substrates, she says.
"The advantage of CNF over other polymers is that it's a bio-based material and most other polymers are petroleum-based polymers. Bio-based materials are sustainable, bio-compatible and biodegradable," Gong says. "And, compared to other polymers, CNF actually has a relatively low thermal expansion coefficient."
The group's work also demonstrates a more environmentally friendly process that showed performance similar to existing chips. The majority of today's wireless devices use gallium arsenide-based microwave chips due to their superior high-frequency operation and power handling capabilities. However, gallium arsenide can be environmentally toxic, particularly in the massive quantities of discarded wireless electronics.
Yei Hwan Jung, a graduate student in electrical and computer engineering and a co-author of the paper, says the new process greatly reduces the use of such expensive and potentially toxic material.
"I've made 1,500 gallium arsenide transistors in a 5-by-6 millimeter chip. Typically for a microwave chip that size, there are only eight to 40 transistors. The rest of the area is just wasted," he says. "We take our design and put it on CNF using deterministic assembly technique, then we can put it wherever we want and make a completely functional circuit with performance comparable to existing chips."
While the biodegradability of these materials will have a positive impact on the environment, Ma says the flexibility of the technology can lead to widespread adoption of these electronic chips.
"Mass-producing current semiconductor chips is so cheap, and it may take time for the industry to adapt to our design," he says. "But flexible electronics are the future, and we think we're going to be well ahead of the curve."
INFORMATION:
John Steeno
608-263-5988
jsteeno@wisc.edu
Boulder, Colo., USA - Lithosphere articles posted 13 and 21 May cover several fascinating locations and geodynamic processes. One study investigates the kinematic evolution of the Himalayan orogen at a site in Nepal. Another paper addresses the "unroofing" of the Klamath Mountains in northern California/southern Oregon, USA. In the East African Rift area, researchers are examining how vegetation mediates slope erosion. Another group focusses on the largest salt lake of the Mediterranean region, Lake Tuz, Turkey.
All recently posted Lithosphere articles are listed below.
Abstracts ...
Stem cell transplant is essential in the care of many blood cancers, but leaves patients requiring in-home care for months after. Frequently the role of caregiver falls to family or other committed members of the patient's support network. Previous work shows dramatically increased stress in cancer caregivers, directly impacting the caregiver and indirectly impacting the cancer patient via reduced quality of care. A randomized control trial funded by the National Cancer Institute by members of the University of Colorado Cancer Center, published in the journal Bone Marrow ...
New York, NY - NYU Langone Medical Center and its Laura and Isaac Perlmutter Cancer Center will have a high profile at the 51st Annual Meeting of the American Society for Clinical Oncology (ASCO), with researchers presenting close to 30 abstracts accepted for oral, poster and publication presentations.
Leading the way are eight oral abstract and poster presentations on melanoma for which an NYU Langone researcher is either a senior, lead or contributing author. While many of these studies are multi-institutional, five poster presentations are led by the Perlmutter ...
Despite early promise of benefits, soy doesn't help lung function
Lifestyle and diet may also affect asthma control
Study highlights importance of placebo-controlled studies
CHICAGO --- Despite previous findings suggesting a link between soy intake and decreased asthma severity, a new study from Northwestern Medicine and the American Lung Association Asthma Clinical Research Network shows soy supplements do not improve lung function for patients with asthma.
The paper, published May 26 in the Journal of the American Medical Association (JAMA), highlights the ...
While most surviving spouses had more depression symptoms following the death of their partner regardless of hospice use, researchers found a modest reduction in depressive symptoms among some surviving spouses of hospice users compared with nonhospice users, according to an article published online by JAMA Internal Medicine.
The Institute of Medicine's report on improving the quality of care near the end of life highlights the need for supporting family caregivers. Core components of high-quality hospice care include counseling services for family members before and ...
Delayed clamping of the umbilical cord to help prevent iron deficiency in infancy was associated with improved scores in fine-motor and social skills in children at age 4, particularly in boys, although it was not associated with any effect on overall IQ or behavior compared with children whose cords were clamped seconds after delivery, according to an article published online by JAMA Pediatrics.
Iron deficiency is a global health issue among preschool children associated with impaired neurodevelopment that can affect cognitive, motor and behavioral abilities. Delaying ...
In an analysis that included more than 70,000 participants from 13 studies, subclinical hyperthyroidism was associated with an increased risk for hip and other fractures including spine, according to a study in the May 26 issue of JAMA. Subclinical hyperthyroidism is a low serum thyroid-stimulating hormone concentration in a person without clinical symptoms and normal thyroid hormone concentrations on blood tests.
Overt hyperthyroidism is an established risk factor for osteoporosis and fractures. Associations between subclinical thyroid dysfunction and fractures are unclear ...
Although some data have suggested that supplementation with soy isoflavone may be an effective treatment for patients with poor asthma control, a randomized trial that included nearly 400 children and adults found that use of the supplement did not result in improved lung function or clinical outcomes, including asthma symptoms and episodes of poor asthma control, according to a study in the May 26 issue of JAMA. Soy isoflavones are plant (soybean) derived chemicals that have anti-oxidant effects.
Increases in asthma prevalence and severity over the last several decades ...
Individually rare but collectively common intermediate-size copy number variations may be negatively associated with educational attainment, according to a study in the May 26 issue of JAMA. Copy number variations (CNVs) are regions of the genome that differ in the number of segments of DNA.
The Database of Genomic Variants catalogs approximately 2.4 million DNA CNVs. Some of them have been previously implicated as causal of a wide variety of traits and conditions. According to background information in the article large (defined as larger than 500 kb), recurrent CNVs ...
In a small study in Chile that included patients with gallbladder cancer, exposure to aflatoxin (a toxin produced by mold) was associated with an increased risk of gallbladder cancer, according to a study in the May 26 issue of JAMA.
In Chile, gallbladder cancer is a leading cause of cancer death in women. Exposure to aflatoxin, a liver carcinogen, is associated with gallbladder cancer in primates. Aflatoxin contamination has been identified in Chile, including in aji rojo (red chili peppers). Aji rojo is associated with gallbladder cancer; however, the association of ...
