Tag Archives: mobile devices

Graphene speakers for mobile devices?

Leave a reply
Credit: American Chemical Society

Credit: American Chemical Society

This speaker doesn’t look its ready for the marketplace yet but it does possess a rather nifty component, graphene aerogel. A Sept. 7, 2016 news item on phys.org briefly describes the scientists’ accomplishment,

Graphene has been hailed as a wonder material since it was first made more than a decade ago. It’s showing up in an increasing number of products, including coatings, sports equipment and even light bulbs. Now scientists are one step closer to making graphene audio speakers for mobile devices. They report in the journal ACS Applied Materials & Interfaces a simple way to fabricate once-elusive thermoacoustic speakers using the ultra-thin material.

A Sept. 7, 2016 American Chemical Society (ACS) news release (also on EurekAlert), which originated the news item, offers an explanation of how these new speakers differ from conventional speakers and a brief description of graphene aerogel (I once saw aerogel described as ‘solid smoke’),

Conventional speakers today rely on many mechanical parts that vibrate to create sound and must be encased in an acoustic cavity — essentially, in a box. But this approach complicates manufacturing and limits where listeners can put their speakers. Scientists have been pursuing ways around this by turning to a principle conceived of more than a century ago: thermoacoustics, the production of sound by rapidly heating and cooling a material rather than through vibrations. Science has caught up to this concept largely thanks to the development of graphene, which is highly conductive and durable. Some efforts to make graphene speakers have succeeded, but making them en masse would be challenging. Jung-Woo Choi, Byungjin Cho, Sang Ouk Kim and colleagues at Korea Advanced Institute of Science and Technology (KAIST) wanted to come up with a simpler approach.

The researchers developed a two-step (freeze-drying and reduction/doping) method for making a sound-emitting graphene aerogel. An array of 16 of these aerogels comprised a speaker that could operate on 40 Watts of power with a sound quality comparable to that of other graphene-based sound systems. The researchers say their fabrication method is practical and could lend itself to mass production for use in mobile devices and other applications. Because the speaker is thin and doesn’t vibrate, it could fit snugly against walls and even curved surfaces.

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

Application of N-Doped Three-Dimensional Reduced Graphene Oxide Aerogel to Thin Film Loudspeaker by Choong Sun Kim, Kyung Eun Lee, Jung-Min Lee, Sang Ouk Kim, Byung Jin Cho, and Jung-Woo Choi. ACS Appl. Mater. Interfaces, 2016, 8 (34), pp 22295–22300 DOI: 10.1021/acsami.6b03618 Publication Date (Web): August 17, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

Cellulose Nanofibrillated Fiber Based Transistors from the University of Wisconsin-Madison

Leave a reply

There’s a team of researchers at the University of Wisconsin-Madison working to substitute silicon used in computer chips with cellulose derived from wood (my May 27, 2015 posting). Their latest effort, featuring mobile electronics, is described in a July 1, 2015 news item on Azonano,

A report published by the U.S. Environmental Protection Agency in 2012 showed that about 152 million mobile devices are discarded every year, of which only 10 percent is recycled — a legacy of waste that consumes a tremendous amount of natural resources and produces a lot of trash made from expensive and non-biodegradable materials like highly purified silicon.

Now researchers from the University of Wisconsin-Madison have come up with a new solution to alleviate the environmental burden of discarded electronics. They have demonstrated the feasibility of making microwave biodegradable thin-film transistors from a transparent, flexible biodegradable substrate made from inexpensive wood, called cellulose nanofibrillated fiber (CNF). This work opens the door for green, low-cost, portable electronic devices in future.

A June 30, 2015 American Institute of Physics news release by Zhengzheng Zhang, which originated the news item, describes the research in more detail,

“We found that cellulose nanofibrillated fiber based transistors exhibit superior performance as that of conventional silicon-based transistors,” said Zhenqiang Ma, the team leader and a professor of electrical and computer engineering at the UW-Madison. “And the bio-based transistors are so safe that you can put them in the forest, and fungus will quickly degrade them. They become as safe as fertilizer.”

Nowadays, the majority of portable electronics are built on non-renewable, non-biodegradable materials such as silicon wafers, which are highly purified, expensive and rigid substrates, but cellulose nanofibrillated fiber films have the potential to replace silicon wafers as electronic substrates in environmental friendly, low-cost, portable gadgets or devices of the future.

Cellulose nanofibrillated fiber is a sustainable, strong, transparent nanomaterial made from wood. Compared to other polymers like plastics, the wood nanomaterial is biocompatible and has relatively low thermal expansion coefficient, which means the material won’t change shape as the temperature changes. All these superior properties make cellulose nanofibril an outstanding candidate for making portable green electronics.

To create high-performance devices, Ma’s team employed silicon nanomembranes as the active material in the transistor — pieces of ultra-thin films (thinner than a human hair) peeled from the bulk crystal and then transferred and glued onto the cellulose nanofibrill substrate to create a flexible, biodegradable and transparent silicon transistor.To create high-performance devices, Ma’s team employed silicon nanomembranes as the active material in the transistor — pieces of ultra-thin films (thinner than a human hair) peeled from the bulk crystal and then transferred and glued onto the cellulose nanofibrill substrate to create a flexible, biodegradable and transparent silicon transistor.

But to make portable electronics, the biodegradable transistor needed to be able to operate at microwave frequencies, which is the working range of most wireless devices. The researchers thus conducted a series of experiments such as measuring the current-voltage characteristics to study the device’s functional performance, which finally showed the biodegradable transistor has superior microwave-frequency operation capabilities comparable to existing semiconductor transistors.

“Biodegradable electronics provide a new solution for environmental problems brought by consumers’ pursuit of quickly upgraded portable devices,” said Ma. “It can be anticipated that future electronic chips and portable devices will be much greener and cheaper than that of today.”

Next, Ma and colleagues plan to develop more complicated circuit system based on the biodegradable transistors.

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

Microwave flexible transistors on cellulose nanofibrillated fiber substrates by Jung-Hun Seo, Tzu-Hsuan Chang, Jaeseong Lee, Ronald Sabo, Weidong Zhou, Zhiyong Cai, Shaoqin Gong, and Zhenqiang Ma.  Applied Physics Letters, Volume 106, Issue 26 or  Appl. Phys. Lett. 106, 262101 (2015); http://dx.doi.org/10.1063/1.4921077

This is an open access paper.

Storytelling for scientists only; self-erasing paper/ink; library news

Leave a reply

I checked out the (Canada) National Science and Technology Week (October 16-25, 2009) website yesterday and found more events (in BC) than the last time I checked in late July/early August. Oddly, one of the events, Storytelling for scientists, is not open to the public. I’m quite disappointed that I’m not allowed to attend as I think it’s a very promising sign of what I hope will be better outreach. ( I got my refusal from someone at the Geological Survey of Canada, which is quite a coincidence since the Survey was recently mentioned here by Preston Manning while discussing his recent speech about science and innovation  in Canada.)

After scanning the science (nanotechnology) news for the last three years, it seems to me that Canadian scientists have been lamentably slow to find ways and means to discuss their work in ways that are engaging and meaningful to people who don’t have a vested interest in the sciences. Yes, there are events for children but I haven’t seen anything much for adults.

Michael Berger over at Nanowerk has written up a very good description of a new technique for creating self-erasing pictures. It caught me eye because of the pop culture reference to Mission Impossible and then there was this,

“While writing with light can be both rapid and accurate, photochromic ‘inks’ are not necessarily optimal for transforming light-intensity patterns into color variations, because they have relatively low extinction coefficients, are prone to photobleaching, and usually offer only two colors corresponding to the two states of photoisomerizing molecules,” explains Bartosz A. Grzybowski, a Professor of Chemical and Biological Engineering and W. Burgess Chair in Physical Chemistry and Systems Engineering at Northwestern University.

I love the idea of ‘writing with light’ and, even better, the explanation of the technology has great clarity. (couldn’t resist the word play)

I have a longstanding interest and fascination with libraries and in light of the recent cuts to the library system here in BC (Canada) and my recent experiences at ISEA (International Symposium on Electronic Art), this item on the Shifted Librarian blog about the mobile devices, libraries, and policy session at the American Library Association (annual meeting?) caught my attention,

Question for Eli: when we talk about mobile devices, we mean digital content. is it a given we’re moving towards this licensing model for digital content, when libraries have traditionally purchased “things” and lending them under first sale doctrine? how do libraries maintain their rights under these threats of DMCA, etc.

Eli: this is really THE question for libraries in the 21st century; holding something of a copy that exists in 10,000 places in the world is worthless – that’s not the value; you have the whole world in your pocket
the rest of the world has skipped the 20th century and gone straight to the 21st; we no longer provide value by providing a copy of something that exists elsewhere
it’s what doesn’t exist anywhere else, which means creating it, which is usually letting your patrons create that
no longer bringing the world to your community, but bringing your community to the world and making it accessible
you’re (the library) the only one that cares about that content being out there
possible future where DRM triumphs & RIAA, etc. get everything they ever wanted and there’s no room for libraries
but could have an uprising against copyright and everything being free to everyone, although this is equally dangerous to libraries
will come down to digital ownership of rights
important not to forget that a major role of the library is to aggregate the buying power of the community and provide access
best thing we can do is produce and assist in the creation of new knowledge
don’t want to get involved in the DRM nightmare and find a value proposition that is meaningful to users in the networked 21st century

If you’re not familiar with the acronyms (I don’t know all of them either), DRM is Digital Rights Management, RIAA is Recording Industry Association of America, and (US) DMCA is Digital Millennium Copyright Act (I had to look up the last two).

This discussion provides an interesting contrast with the item about the cuts to the BC library system on the Think City website. Both are concerned with purchasing power and community access but one from the perspective of our mobile device future and one from the perspective of a 90-year old system that needs to be maintained.