NanoPropulsion

Stephen J. Ebbens

Jonathan Howse

The current state of the art in nanopropulsion devices was recently reviewed by Ebbens and Howse in an article last Friday.^[SoftMatter] A short summary of the nano- systems is presented below with video action shots when I could find them.

The Whitesides

Catalyst: Pt
Fuel: H₂O₂
Propulsion: Bubble propulsion
Terrain: Aqueous meniscus
Max Speed: 2 cm/s
Mitch’s Name: The Karl Benz (since it was the first)
Article: Autonomous Movement and Self-Assembly

The Sen-Mallouk-Crespi

Catalyst: Pt
Fuel: H₂O₂
Propulsion: Self electrophoresis/Interfacial tension
Terrain: Settled near boundary in aqueous solution
Max Speed: 6.6 um/s
Mitch’s Names: The Ford Mustang of nanopropulsion. (It is a hot rod, get it?)
Article: Catalytic Nanomotors: Autonomous Movement of Striped Nanorods

The Jones-Golestanian

Catalyst: Pt
Fuel: H₂O₂
Propulsion: Pure self diffusiophoresis
Terrain: Free aqueous solution
Max Speed: 3um/s
Mitch’s Name: The Volkswagen Beetle
Article: Self-Motile Colloidal Particles: From Directed Propulsion to Random Walk

The Mano-Heller

Catalyst: Glucose oxidase and Biliruben oxidase
Fuel: Glucose
Propulsion: Self electrophoresis
Terrain: Aqueous meniscus
Max Speed: 1 cm/s
Mitch’s Name: The Komatsu Truck (because it is huge)
Article: Bioelectrochemical Propulsion

The Feringa

Catalyst: Synthetic catalse
Fuel: H₂O₂
Propulsion: Bubble/interfacial
Terrain: Acetonitrile solution
Max Speed: 35 um/s
Mitch’s Name: The F150 (has some exhaust issues)
Article: Catalytic molecular motors: fuelling autonomous movement by a surface bound synthetic manganese catalase

The Sen-Mallouk

Catalyst: Pt (CNT) (+cathodic reactions at Au)
Fuel: H2O2/N2H4
Propulsion: Self electrophoresis
Terrain: Settled near boundary in aqueous solution
Max Speed: 200 um/s
Mitch’s Names: The Ford Mustang GT (has more kick than the regular version)
Article: Bipolar Electrochemical Mechanism for the Propulsion of Catalytic Nanomotors in Hydrogen Peroxide Solutions

The Feringa v2

Catalyst: Glucose oxidase and catalse
Fuel: Glucose
Propulsion: Local oxygen bubble formation
Terrain: Free aqueous buffer solution
Max Speed: 0.2–0.8 um/s
Mitch’s Name: The Chevrolet Nova (more hot rod action)
Article: Autonomous propulsion of carbon nanotubes powered by a multienzyme ensemble

The Gibbs-Zhao

Catalyst: Pt
Fuel: H₂O₂
Propulsion: Bubble release mechanism
Terrain: Aqueous solution
Max Speed: 6 um/s
Mitch’s Name: The Rover
Article: Autonomously motile catalytic nanomotors by bubble propulsion

The Bibette

Engine: External magnetic field
Propulsion: Flagella
Terrain: Aqueous solution
Max Speed: unknown
Mitch’s name: The BMW Mini E (because there is no such thing as a magnetic car)
Article: Microscopic artificial swimmers

The Sagués

Engine: External magnetic field
Propulsion: Doublet rotation coupling with boundary interactions
Terrain: Settled near boundary in aqueous solution
Max Speed: 3.2 um/s
Mitch’s Name: The Smart ED
Article: Magnetically Actuated Colloidal Microswimmers

The Fischer

Engine: External magnetic field
Propulsion: Propeller drive
Terrain: Aqueous solution
Max Speed: 40 um/s
Mitch’s Name:
Article: Controlled Propulsion of Artificial Magnetic Nanostructured Propellers

The Najafi-Golestanian

Engine: Conformation changes in linking units
Propulsion: Time irreversible translations
Terrain: Free solution
Max Speed: ?
Mitch’s Name: The Eternal Concept Car
Article: Propulsion at low Reynolds number

Some devices that were not included by the authors of the review article, but should definitely be included in any list like this are below:

The Gracias

Engine: External magnetic field
Propulsion: Brute Force
Terrain: Aqueous solution
Max Speed: ?
Mitch’s Name: The Truck Cranes
Article: Tetherless thermobiochemically actuated microgrippers

Tetherless Microgrippers Grabs Tissue Sample – Watch today’s top amazing videos here

The Nelson

Engine: External electromagnetic fields
Propulsion: Flagella
Terrain: ?
Max Speed: 18 um/s
Mitch’s Name: The Tesla Roadster (simply awesome)
Article: Characterizing the Swimming Properties of Artificial Bacterial Flagella

Artificial Sperm – Watch more funny videos here

Link to Review Article: In pursuit of propulsion at the nanoscale

Mitch

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Long-term Experiments

I recently read this Nature article, where is described what is probably one of the longest experiments ever to be conducted. A population of E. coli was kept for 20 years (!) in a nutrient solution (low on glucose), and samples were taken and deep-frozen after 2000, 5000, 10000, 15000, 20000 and 40000 generations. The authors sequenced the genome of the sample bacteria to investigate the rate of mutations.

Up to generation 20K, the number of mutations grew steadily to a total of 45. The adaptation to the environment, however, only increased strongly in the beginning. It was concluded that the most beneficial mutations were the first to occur. After generation 20K, a change in the mutT gene caused a rapid increase in the mutation rate to result in 653 mutation at generation 40K, but with a neutral signature, i.e. no further adaptation.

What I find most fascinating about this extreme long-term experiment is the confidence of the researchers that it would be possible to analyze the genes at a later point; this was not at all self-evident in the late ’80s! In addition, some work had to be done each day, for twenty years. What if the power had failed for a week or so? Of course, this unique opportunity to watch evolution as it happens is very intriguing.

An experiment that took even longer was awarded this year’s Ig Nobel Prize in medicine: Donald L. Unger of Thousand Oaks, CA, cracked the knuckles of his left hand, but not his right hand, every day for 50 years to see if knuckle-cracking leads to arthritis. After this time, both hands were fine, so he concluded: “While a larger group would be necessary to confirm this result, this preliminary investigation suggests a lack of correlation between knuckle cracking and the development of arthritis of the fingers.” Apparently, the experiment must be repeated.

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Joking in a Nature journal?

Was reading this earlier this evening on the hobby science forum Sciencemadness.org –it’s amusing.

Read the letter carefully.

Well, let’s hope this is a joke.

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Condensed Print Format

My boss has pointed out this piece of news covered by C&EN. Apparently, starting from July, all ACS journals will be printed in a “rotated and condensed” format, that is two pages on one printed page in landscape format. This is an effort to reduce printing and distribution costs.

In my opinion, this change is just one further step towards purely electronic journals that are not printed at all. I think this will deeply affect the way we present our data and how we look at formatting. Preparing a manuscript in a way meant for printing is different from one which will never appear in print. Some may welcome this change because it saves paper, others will probably miss the possibility of flicking through a new issue of JACS. Although I rarely go to the library to pick up a printed journal, I admit to reading printouts very often (see this post).

Update: Apparently, in 2010 the print versions will stop completely, with the exception of JACS, Acc. Chem. Res. and Chem. Rev. See also Nature News.

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Scientific Misconduct

This nature article discusses the results of a survey about scientific misconduct, while an editorial makes some comments.

Quote: “The 2,212 researchers we surveyed observed 201 instances of likely misconduct over a threeyear period. That’s 3 incidents per 100 researchers per year. A conservative extrapolation from our findings to all DHHS-funded researchers predicts that more than 2,300 observations of potential misconduct are made every year.” Almost 9% of the respondents had witnessed some sort of misconduct, and 37% of those incidents went unreported.

The authors conclude that, besides protecting the whistleblowers better, it is necessary “to create a zero-tolerance culture”. The editor, however, holds the opinion that one also needs to take a look at “the environment that has allowed misconduct to flourish”. In his opinion, there should be the possibility of finding a solution without ruining the career of a scientist, especially in mild cases.

I tend to follow the editor’s reasoning. In my opinion, the zero-tolerance culture already exists to a certain extent, because a scientist convicted of, e.g. faking data, can forget about his career. But the result of such a policy is clear: no-one wants to blow the whistle on a colleague, because they don’t want to end somebody else’s career and because they will make themselves very unpopular. The real problem is the way misconduct is treated at the moment: we want to identify the guilty scientist, and punish him/her.

While this makes sense for the worst cases of fraud, in milder cases one should try and ask the question *why* the misdeed was done. Take, for example, the way hospitals treat mistakes nowadays: they try to find out how it could happen, and how it can be avoided in the future. This is very sensible, because it treats the problem in a proactive way: instead of reacting to the incident by punishing somebody, future incidents are reduced by tackling the things that cause them in the first place.

If there is a lot of pressure to produce as much data as possible in a research group, it is tempting to cut a corner once in a while. Can this not partly be considered the prof’s fault? In a similar way, one should address the working atmosphere in the group in question. The problem with the academic system is that there is no informal institution to turn to, besides your boss, if you are to witness a case of scientific misconduct. So we fall back to the old issue: the only person you can contact in case of problems has all the power over you.

At the University of Toronto, a “Graduate Student Oath”, similar to the Hippocratic Oath, has been tried as a means to strengthen scientific ethics (Science). Although this is an interesting idea, I doubt it will change the behaviour of people very much.

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Discovery of Mg-40, Al-42, and Al-43

Baumann et al. have recently reported the discovery of three new isotopes ⁴⁰Mg, ⁴²Al, and ⁴³Al. The discovery is notable for producing an isotope that neither the finite range droplet model (FRDM) nor the Hartree-Fock-Bogoliubov (HFB-8) predicted should be bound.

Of the 3 isotopes, the discovery of ⁴²Al is an unexpected surprise and thusly the most fascinating. As we all know from undergraduate nuclear chemistry the Weizsäcker’s formula contains a pairing term (d) approximately equal to 34*A^-3/4 MeV. The term increases the binding energy for an even number of protons (Z) and neutrons (N), decreases it for an odd Z and N, and of course is zero for an odd atomic number (A). ⁴²Al contains 13-protons and 29-neutrons, lies on the extreme neutron-rich side, and thus was not predicted to exist in a bound state.

Theory can be seen to be in contradiction from experimental data as seen below.

Reprinted by permission from Macmillan Publishers Ltd: Nature 449, 1022 – 1024 (25 Oct 2007).

To the immediate left of the ⁴³Al dot is the collection of ⁴²Al events. The ⁴³Al event had a probability of ~2 x 10^-3 of arising from the Al-42 cluster of events.The tantalizing conclusion of this work is that the neutron-drip line may reside further than even the next generation nuclear facilities could explore for Z>12.

Link to article: http://dx.doi.org/10.1038/nature06213

Mitch

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ACS Boston 2007: Free Alcohol and Free Stuff

Free Alcohol
Saturday there was free food and alcohol at the Marriott for the Younger Chemist Committee (YCC). It was sponsored by the ACS web team. Fortunately, there weren’t many people there so I got more than my share of egg rolls and free booze. That night at the poster session, there was also free alcohol and free turkey which is an interesting combination of food and drink when its already late at night and you’ve been looking at talks all day.

Monday I will be trying to score some more free food and drink at the CHED poster session 2:30-4, I don’t know whether there will be anything, but I’ll shortly find out. The Nuclear division has their social hour at 7-9pm tonight, and there should be plenty of free alcohol there. Since, scimix is from 8-10, I’ll be there from 9 on.

Free Stuff
Monday is the first day the exposition opens up to us regular folk. The best booths by far have been the following.

Elsevier: Free personal fan that lights up and says, “I’m hot”. Which is also true… thermally at least.

Corning: Free M&Ms in their new 200mL plastic vessel

Strem: Which has a nice periodic table for your desk. The best thing about it, it’s actually up to date with the newest transactinides (i.e. Roentgenium).

ACS pubs: Free issue of ACS Nano. I dropped by and was hoping to catch an editor there, but the very cute girl from marketing that was managing the desk said they all went home for the day. Mind you, I was there at 10:30AM and the exposition only opened at 9:00AM. However, I did see Ivan there, but he looked overly excited about Hoffman’s poetry reading, which in my book is a red flag and signaled it was time to move on.

Nature: Free issue of Nature and Nature Nanotechnology: I went to that booth to try to meet some of their editors. But, no one there knew where they were or what time they were going to show up.

Mitch

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