Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

UCSD Chemists Develop Self-Assembling Silicon Particles

26.08.2003


A First Step Toward Robots the Size of a Grain of Sand


Image of smart dust particles surrounding a drop of hydrophobic liquid in water
Credit: Jamie Link, UCSD



Chemists at the University of California, San Diego have developed minute grains of silicon that spontaneously assemble, orient and sense their local environment, a first step toward the development of robots the size of sand grains that could be used in medicine, bioterrorism surveillance and pollution monitoring.

In a paper to be published in September in the Proceedings of the National Academy of Sciences, which will appear in the journal’s early on-line edition this week, Michael Sailor, a professor of chemistry and biochemistry at UCSD, and Jamie Link, a graduate student in his laboratory, report the design and synthesis of tiny silicon chips, or “smart dust,” which consist of two colored mirrors, green on one side and red on the other. Each mirrored surface is modified to find and stick to a desired target, and to adjust its color slightly to let the observer know what it has found.


“This is a key development in what we hope will one day make possible the development of robots the size of a grain of sand,” Sailor explains. “The vision is to build miniature devices that can move with ease through a tiny environment, such as a vein or an artery, to specific targets, then locate and detect chemical or biological compounds and report this information to the outside world. Such devices could be used to monitor the purity of drinking or sea water, to detect hazardous chemical or biological agents in the air or even to locate and destroy tumor cells in the body.”

To create the smart dust, the researchers use chemicals to etch one side of a silicon chip, similar to the chips used in computers, generating a colored mirrored surface with tiny pores. They make this porous surface water repellent, or hydrophobic, by allowing a chemical that is hydrophobic to bind to it. They then etch the other side of the chip to create a porous reflective surface of a different color and expose the surface to air so that it becomes hydrophilic, or attractive to water.

Using vibrations, they can break the chip into tiny pieces, each about the size of the diameter of a human hair. Each piece is now a tiny sensor with opposite surfaces that are different colors, with one attracted to water and one repelled by water and attracted to oily substances.

When added to water, the “dust” will align with the hydrophilic side facing the surface of the water and the hydrophobic side facing toward the air. If a drop of an oily substance is added to the water, the dust surrounds the drop with the hydrophobic side facing inward. In addition to this alignment, which will occur in the presence of any substance that is insoluble in water, a slight color change occurs in the hydrophobic mirror. The degree of this color change depends on the identity of the insoluble substance. The color change occurs as some of the oily liquid enters the tiny pores on the hydrophobic side of the silicon particle.




PNAS

Sailor Research Group

UCSD Department of Chemistry

Prior UCSD Research






“As the particle comes in contact with the oil drop, some of the liquid from the target is absorbed into it,” Sailor explains. “The liquid only wicks into the regions of the particle that have been modified chemically. The presence of the liquid in the pores causes a predictable change in the color code, signaling to the outside observer that the correct target has been located.”

The hydrophilic side of the chip behaves in a similar way; it changes color according to the identity of the hydrophilic liquid it contacts. While each individual particle is too small to observe the color code, the collective behavior of the particles facilitates the detection of the signal.

This research effort, funded by the National Science Foundation and the Air Force Office of Scientific Research, builds on previous work by the Sailor group to develop various types of sensing devices from silicon chips. A year ago, the group reported the development of silicon particles with a single sensing surface.

Link, the first author on the paper, says the dual-sided particles have the additional benefit of being able to collect at a target and then self-assemble into a larger, more visible reflector that can be seen from a distance. “The collective signal from this aggregate of hundreds or thousands of tiny mirrors is much stronger and more easily detected than that from a single mirror,” she points out. “The tendency of these particles to clump together will therefore enable us to use this technology for remote sensing applications.”

Sherry Seethaler | UCSD
Further information:
http://ucsdnews.ucsd.edu/newsrel/science/smartdust.htm

More articles from Life Sciences:

nachricht Are there sustainable solutions in dealing with dwindling phosphorus resources?
16.10.2017 | Leibniz-Institut für Nutzierbiologie (FBN)

nachricht Strange undertakings: ant queens bury dead to prevent disease
13.10.2017 | Institute of Science and Technology Austria

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

Im Focus: New nanomaterial can extract hydrogen fuel from seawater

Hybrid material converts more sunlight and can weather seawater's harsh conditions

It's possible to produce hydrogen to power fuel cells by extracting the gas from seawater, but the electricity required to do it makes the process costly. UCF...

Im Focus: Small collisions make big impact on Mercury's thin atmosphere

Mercury, our smallest planetary neighbor, has very little to call an atmosphere, but it does have a strange weather pattern: morning micro-meteor showers.

Recent modeling along with previously published results from NASA's MESSENGER spacecraft -- short for Mercury Surface, Space Environment, Geochemistry and...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

Conference Week RRR2017 on Renewable Resources from Wet and Rewetted Peatlands

28.09.2017 | Event News

 
Latest News

A single photon reveals quantum entanglement of 16 million atoms

16.10.2017 | Physics and Astronomy

The melting ice makes the sea around Greenland less saline

16.10.2017 | Earth Sciences

On the generation of solar spicules and Alfvenic waves

16.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>