James Tyrrell: December 2008 Archives

Tree

Happy holidays and see you again next year. For dates, check out the MRS website.

nanotechweb.org print supplement

Pick up your free nanotechweb.org print supplement packed with our most popular content by visiting the IOP Publishing booth #104 at this year's MRS Fall meeting.

Asylum's Cypher makes its debut

Walking up and down the aisles, I must have counted well over a dozen scanning probe microscope (SPM) makers from across the globe with products to promote. What started as a "home built" instrument has matured into a plug-and-play piece of product design.

At the exhibit, most of the SPMs on show are more than just display items. More and more firms are encouraging attendees to turn up with a sample for imaging, which makes the MRS fall meeting a great opportunity to find out which SPM works best for you.

When it comes to flattening vertically aligned carbon nanotubes (CNTs), the diameter of the "rolling pin" is critical. As Sameh Tawfick explained in his talk yesterday afternoon, if the pin is too large then it buckles the CNTs and destroys the alignment. If the roller is too small then it gets caught up in the forest of nanotubes and leads to patchy densification.

The team's goal is to prepare a well defined sheet of the material that can then be used for contact printing structures such as interconnects. And who would be interested in this? Well, Intel for one, if the author affiliations provide a clue.

Some more facts and figures just in - Tawfick revealed that a 0.6 mm pin is ideal for a 1 mm high CNT forest. Once flattened, the structures are dipped in solvent to further densify the material before transfer printing.

Related story -

Inventors roll out nanotube paper
http://nanotechweb.org/cws/article/tech/33089

Aisle 600

Show floor area 600 has been dubbed the "Nano" aisle at this year's exhibit. Attendees taking a stroll in this direction are treated to super plush carpeting and can stop by at the open seminar area. Here, industry experts take turns to give advice on a range of nano-related topics such as image analysis, AFM probe selection and new tools for extreme environments, all in easy-to-handle 25 minute slots. The snappy tag line for the presentations, which run from Tuesday - Thursday, is "No selling - just information on how does it work and can I make use of it?"

Room 302, Hynes convention centre

Room 302 was the venue for Zhong Lin Wang's explanation of nanopiezotronics - the use of piezoelectric nanowires in electronics.

Wang showed the audience how semiconducting nanowires can be configured to form a piezoelectric diode, a humidity sensor, a piezoelectric transistor and a nanogenerator. What's more, if you make the nanowire out of CdS then the nanogenerator becomes light sensitive, providing power only when illuminated.

Related stories -

Entwined nanowires generate electricity
http://nanotechweb.org/cws/article/tech/32882
Nanowires promise battery free power
http://nanotechweb.org/cws/article/indepth/32144

Workout

I've already seen a few attendees snoozing in the hotel lobby. So, I'm going to pitch in with a couple of MRS survival tips. Number one, don't neglect the body. The conference runs for five days, or six if you signed up to the workshops on Sunday. Number two, drink lots of coffee.

Symposium T

Sitting in on symposium T, it was time to find out more about mobile energy - specifically, batteries that can be bent.

Pritesh Hiralal from Cambridge University, UK, is part of a team working on all-solid thin-film batteries for portable applications, or as he phrased it - flexible batteries for flexible electronics.

Hiralal's approach is to redesign a standard zinc-carbon cell layer-by-layer and the latest prototype features a combination of electrospun carbon fibre cloth, single-walled carbon nanotubes and ceramic nanoparticles.

There's more work to be done, but the initial results are encouraging and show that the flexible cell is able to withstand several bending cycles.

Howard Wang of Binghampton University, US, gave an update on the performance of sintered metal nanoparticles. The team is pulling together technology to realize high-performance roll-to-roll electronics and has been successful in using inkjet-printed metal nanoparticles to interconnect devices on the flexible and often temperature sensitive substrates.

Wang sources his particles from NanoMas - a supplier of silver nanoparticles measuring 2 nm in diameter. The reduction in melting point with particle size means that the researchers can run their sintering process at just 100 degC, which opens the door to a wide range of roll-to-roll compatible films.

Related stories on nanotechweb.org -

Electrical sintering joins up nanoparticles
http://nanotechweb.org/cws/article/tech/33932
Laser sintering strikes gold with nanoparticle ink
http://nanotechweb.org/cws/article/tech/19932

Earlier in the day, I caught up with Anita B. Miller, manager of marketing and member services at the MRS (and more importantly for me, the distributor of badges to members of the press) and it sounds like the organizers are expecting well over 5000 attendees this year's event.

There's certainly plenty to see once you get here with 45 technical symposia, a staggering 4,700 oral and poster presentations and a show floor packed with 225 international exhibitors. But, if that sounds like a lot then wait until next year. "In 2009, we're planning to hold 50 technical symposia," Miller told me. "You're going to need roller skates to see it all."

Rogers' colleague at the University of Illinois at Urbana-Champaign, Heung Cho Ko wrapped up the morning session with the story behind the group's electronic eye camera. The name comes from the fact that the imaging device features a curved detector just like the eye - a geometry that can produce great picture quality from a simple lens.

You've probably already guessed, but the structures behind the shaped image sensor are none other than silicon nanoribbons.

I spoke with Heung Cho Ko after the presentation to find out a bit more about the group's prototype device, which he had placed on display. Ko hopes that the simple lens configuration will lead to extremely affordable imaging systems such as cameras in the near term and then vision-based robotics as the technology matures.

Related story -
Silicon camera goes curvilinear
http://optics.org/cws/article/research/35340

Symposium G

The technical program got off to a flying start as John Rogers captured the audience's imagination with the idea of making stretchy silicon.

First, you've got to thin the silicon down to make it flexible. "There are basic etching tricks to do this," he said, revealing SEM images to back up the claim. "What you end up with is a large quantity of nanoribbons."

Next, you use a stamping process to move the thin strips of silicon into position on a substrate. "The wafer becomes an inking pad," explained Rogers. "And you dry transfer print the nanoribbons on to your device substrate."

Saving the best until last, he popped up a slide showing wavy silicon ribbons rising up and down across a rubbery PDMS film. The secret to creating the structure is to stamp the nanoribbons on to a pre-stretched substrate. When the surface is allowed to relax and shrink in size, the silicon buckles into a springy network that can be both stretched and compressed by as much as 50%. According to Rogers, in tests the substrate will often rupture before the silicon.

The team has already used the technique to make simple CMOS circuits, which leads me nicely on to my next post...