Post Tagged with: "C&EN"

Light Powered Motor and Experiment Vlogging

Most of you probably read the last issue of C&EN with the spiffy carrot loving cover story (good for me because I love carrots, but have never tried those ugly-looking BetaSweets). Inside, however, there was an extremely interesting little article in the “Science and Technology Concentrates” about light-driven pulleys turning a plastic motor.

Now photo mobile polymer materials have been around for quite a while, at least from my perspective seeing as how I wasn’t even in highschool when the big Nature paper came out. Some might remember the Nature 1999 Sep 9;401(6749):152-5 Koumura et al. paper titled “Light-Driven monodirectional molecular rotor”. Although back then, the rotation was monodirectional around a C-C double bond in a chiral, helical alkene. It was activated by UV light or a change in temperature and the motor was based on light-induced cis-trans isomerizations that caused 180 degree rotations followed by thermally controlled helicity inversions, which basically nullified half a rotation. Four isomerizations resulted in 1 complete cycle.

Well this was pretty darn cool but we’ve come a long way since then. As expected, and as Koumura said, structurally modified chiral alkenes played the central role in the development of these molecular motors that were beginning to interest the MEMS people (MEMS stands for Micro-Electromechanical Systems…I am pretty sure).

In J Am Chem Soc. 2003 Dec 10;125(49):15076-86, ter Wiel MK et al. introduced the worlds smallest artificial light-driven motor using 28 carbon atoms and 24 hydrogen atoms.

Reprinted with permission from American Chemical Society: Journal of the American Chemical Society (Nov. 2003).

It also had a dramatic speed increase over the original designs, at a whopping 18s half-life at the fastest step. Even if it wasn’t going to be turning any relevant loads any time soon, it was a dramatic improvement over the original concept 4 years earlier. Still, even though some clever O-chem tricks made the motor better, it still operated on the same 4-step cycle that Koumura’s did back in 99′. Even recently, in Org. Biomol. Chem., 2008, 6, 507 – 512, DOI: 10.1039/b715652a, Pollard et al. report on substituting naphthalene moieties for phenyl moieties, in order to better control the speed of the motors, and to enable the design and synthesis of more complex systems.

Meanwhile, the MEMS people came up with interesting designs similar to this:

“A five micron wide resin structure, with a shape resembling a lawn sprinkler, rotates when illuminated by a laser beam. Tiny rotors like this one may someday power micromechanical systems (MEMS), or twist molecules to measure their mechanical properties.” Reported by: Péter Galajda; Pál Ormos, Applied Physics Letters, 8 January, 2001.

There was quite a bit of work done focusing on creating rotors that responded to laser light, although the practical applications of such devices aren’t as numerous as the devices that…well don’t require a coherent, collimated, polarized light beam to operate. Or at least they weren’t until Peidong Yang’s came around with his nanolasers.

Unfortunately, all of these motors share the drawback of being unidirectional. It was until recently, with Ikeda’s et al. paper in Angew. Chem. Int. Ed. 2008, 47, 4986, that a very cool and new method for directly converting light into mechanical work. Basically they drew on the fact that azobenzene derivatives, when incorporated into liquid crystals, can have an isotropic phase transition induced isothermally by irradiation with UV light to cause trans–cis photoisomerization, and that the reverse transition can be induced by irratiation with visible light to cause cis-trans back-isomerization. This photoinduced phase transition
led to successfully reversible deformations of liquid crystal elastomers containing azobenzene chromophores just by changing the wavelength of the incident light.

Now this by itself doesn’t a motor make. There was one large problem: the liquid crystal elastomer had to be made into a film or “belt” for a motor. However, the LCE film by itself wasn’t mechanically strong enough and tended to crack after short light irradiation at high intensities. So to fix this issue, they simply laminated the LCE film with flexible polyethylene sheets. I love this type of simple solution to what could have been a convoluted problem. This is very much like what Mitch and I tend to do.

*Note that they did do a study of increasing light intensity and it’s correlation to the mechanical force generated by the film. They found that “the maximum force and the increment rate of the generated force are enhanced with an increase of the light intensity.”*

So what happened? Well check this out:

Thats right. That is an actual light-driven motor NOT on the micro-scale. The diameter of those pulleys are 10mm on the left and 3 mm on the right. Sure it isn’t going to be competing in any races at the moment, but it could still be amazingly useful in the future. Light, straight to DC? That would be pretty darn awesome.

PS. Tomorrow is the first day of the experiment Mitch and I are running. Since we can, we will be broadcasting the first live cyclotron experiment out over the interweb. This may be one of the first live nuclear physics experiments broadcasted. Other then that, it is just cool. SO we will have it up all 24 hours as a “live vlog”.

Feel free; hell feel obligated to stop by, leave a comment, chat, ask questions, offer constructive or destructive criticism, whatever. Maybe ACS will pick this up as a new way to present new research: present it as it happens! Live!!!

European Chemistry Commercials

This video was recently mentioned at the C&EN blog: Chemistry As A Party. The video feels overtly corny, but those wacky Europeans can have a strange taste in humor. 😉 Anyways, have a look for yourself.

Chemistry Can Be Fun

Other Coverage: Creative Review Blog, BoingBoing-Chemistry Party science education video, Practical Transmutations, Mad Chemist Chick-From Around the Web
Video Commissioned by: Marie Curie Actions


By May 17, 2008 15 comments Uncategorized

Undergrads finally have a reason to join ACS

When approached by undergraduates whether they should join ACS, I usually advise them to save their money. In the current setup, student members are 2nd class members of the ACS hierarchy. The benefits for being an undergraduate member are none, I really can’t think of any and I’ve been a student member for awhile. At the recent ACS-New Orleans meeting a rules change was passed to give undergraduates and graduate students almost full membership status. The only limitation, from perusing the bylaws, is they can’t hold an elected national office.

It’ll be interesting to see if this has the effect of incorporating student members into the governance structures of ACS. Being a graduate student I still find it impossible to get onto any ACS committees. Which is understandable, why would a division committee want none PhDs. We’ll see if this really changes anything.

C&EN coverage by Linda Raber: Council Approves Membership Overhaul
Constitution and Bylaws affected: Petition on Membership Categories & Requirements


Update: Here is a list of councilors that voted against Student Members. 😉

Ex Officio Councilors: Gordon L. Nelson; Attila E. Pavlath
Agricultural & Food Chemistry: Michael J. Morello, Sara J. Risch
Analytical Chemistry: Alanah Fitch
Biological Chemistry: Felicia A. Etzkorn
Chemical Health & Safety: Kathryn G. Benedict
Environmental Chemistry: Martha J. M. Wells
History of Chemistry: Mary Virginia Orna
Industrial & Engineering Chemistry: Spiro D. Alexandratos; Kenneth L. Nash
Medicinal Chemistry: Peter R. Bernstein; Gunda I. Georg; Richard A. Gibbs
Physical Chemistry: Paul W. Jagodzinski
Professional Relations: John K. Borchardt
Rubber Division: Robert A. Pett
California: Rollie J. Myers Jr.; James M. Postma
Central North Carolina: Robert A. Yokley
Central Texas: Barry J. Streusand
Central Utah: Steven A. Fleming
Central Wisconsin: C. Marvin Lang
Chattanooga: Maurice R. Smith
Chicago: Mark C. Cesa; David S. Crumrine; Herbert S. Golinkin; Russell W. Johnson; Barbara E. Moriarty
Cleveland: Samina Azad
Colorado: Sandra J. Bonetti; Susan M. Schelble
Columbus: Theresa A. Huston
Connecticut Valley: Tyson A. Miller; Ronald J. Wikholm
Detroit: Walter O. Siegl
Idaho: Charles A. Allen
Inland Northwest: Jeffrey A. Rahn
Kalamazoo: Lydia E. M. Hines
Kentucky Lake: S. K. Airee
Louisiana: Jack H. Stocker
Louisville: James F. Tatera
Maryland: Charles F. Rowell
Minnesota: Lynn G. Hartshorn; Sarah M. Mullins; Wayne C. Wolsey
Nebraska: Michael D. Mosher
North Carolina: James L. Chao; Alvin L. Crumbliss
North Central Oklahoma: Joe D. Allison
North Jersey: Michael M. Miller
Northeastern: Patrick M. Gordon; S. B. Rajur; Alfred Viola
Pensacola: Allan M. Ford
Portland: Angela Hoffman
Rock River: Dennis N. Kevill
Santa Clara Valley: Linda S. Brunauer; Ferenc Makra
Savannah River: Christopher J. Bannochie
Sioux Valley: Jetty L. Duffy-Matzner
South Central Missouri: Frank D. Blum
South Jersey: Guenter Niessen
Southeastern Pennsylvania: James Foresman
Southern California: Rita R. Boggs; Stanley H. Pine
Upper Peninsula: Ann L. Kemppainen
Wabash Valley: Frank A. Guthrie
Western Michigan: Mark Thomson

By May 5, 2008 3 comments Uncategorized

Irradiation to enhance food safety

Does anyone remember the E. Coli breakout back in 2006? I do. There has never been a quicker way to convince a 19-year-old to eat vegetables until you take lettuce out of their sandwiches for a couple of months.

According to the LA Times report[1], these greens are washed in potent chlorine bath, often up to three times, before they are bagged and shipped to the retailer. This standard procedure has a reported 90% effectiveness in killing the microorganisms that may cause harmful effects to the human body.

I don’t know about you, but I would rather not take that 10% chance to get sick. In the single breakout of E. Coli due to cross contamination with the cattle back in 2006, 200 people became ill and three lost their lives. That’s the 10% chance that nobody should have to take.

This past month at the ACS National Meeting in New Orleans, researchers from the USDA presented their findings and results of radiation treatment of fresh produces. Irradiation of high energy beams of photons or electrons, said the scientist, can disrupt the DNA of these pathogens. While the chlorine rinse offers a 90% effectiveness in killing bacterias on the surface of the leaves, it is not able to penetrate beneath the surface. Irradiation method has a reported >99.9% effectiveness in wiping out pathogens such as E. coli, salmonella and listeria, and the high energy beams allows penetrating power that works inside and outside the leaves.

Some members of the scientific community are calling irradiation one of the “few intervention steps that indeed can penetrate the leaf surface and kill microorganisms.”

Irradiation for enhancement of food safety is permitted for some hamburger meat, poultry and spices, but not for fruits and vegetables. However, there has not been any health problems associated with eating irradiated food. So why is FDA steering away from adopting an improved method that could potentially save lives?

Consumer experts and food safety researchers offer some of their speculations:

1. Irradiation may damage the apparence of the product, which may not be as appealing to the customers
2. Nobody would buy lettuce from a bag with a radiation sticker
3. The treatment could shorten shelf lives of the products
4. Technically, irradiated produces cannot be certified organic

Though reasonable, it is hard to believe that the above mentioned points would stop either FDA or independent research institutes from further investigating in a method that could possibly be so much more potent in eradicating pathogens than the existing practice. Perhaps these novel ideas would not suffer as much if we could deliver more transparent and correct ideas regarding the applications of radiation.

Using innovative ideas to improve the quality of our everyday lives, isn’t that what science is all about?


[1] USDA scientists say irradiation could be key to food safety

P.S. True to scientific spirit and for the benefit of the minorities out there, I will summarize and translate my discussion in lolcat. I can has radeashuns: on ur vegitablez, keelin ur baktiriaz.

Edit: Originally mentioned by Bethany Halford and Lisa Jarvis in Chemistry Newsbytes.

By April 22, 2008 9 comments nuclear chemistry, science news