Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Tiny machines need even tinier lubricants

30.03.2004


Tiny machines built as part of silicon chips are all around us, and their need for lubrication is the same as large machines such as automobile engines, but conventional lubricants, like oils, are too heavy for these micro electromechanical systems (MEMS), so Penn State researchers are looking to gases to provide thin films of slippery coating.

MEMS today are mostly found in automobile air bags as the sensor that marks sudden deceleration and triggers airbag use. They can also take the form of tiny motors that move mirrors to focus a beam of light, or tiny nozzles that provide minute droplets of ink in ink jet printers.

"Traditionally, the lubrication industry uses viscose liquids to lubricate – oils or oils and additives – to reduce friction and increase efficiency," says Dr. Seong H. Kim, assistant professor of chemical engineering. "However, oil-based lubricant use in MEMS causes a power dissipation that is unacceptable."



Because MEMS are so small, with parts about the width of a human hair, and exert so little force, from almost none to the equivalent of the Earth’s gravity on a thousand red blood cells, conventional lubricants simply do not work. Oil molecules are usually large and relatively heavy. They not only stop the MEMS dead in their tracks, but also cannot infiltrate the microscopic cracks and crevices of the machines.

The current trend in MEMS is to use solid lubricants -- thin-film coatings of diamond-like carbon or self-assembling monolayers of methylated or fluorocarbon compounds. While solids provide a thin enough layer, they do not always coat the entire mechanism. They are also subject to wear because of their thinness and are not self-healing or replenishing.

"The fact that the solid coatings work tells us that for lubrication, all we need is a thin film," Kim told attendees today (Mar. 29) at the 227th National Meeting of the American Chemical Society.

Kim and Dr. Kenneth Strawhecker, postdoctoral fellow in chemical engineering, investigated delivering a thin coating of liquid lubricant by condensing a gas onto the surface of the MEMS. The researchers investigated alcohols including ethanol, propanol, butanol and pentanol.

The researchers chose alcohols because they are both hydrophilic and hydrophobic, easily combining with water on one end and combining with other compounds on the other. At the incredibly low forces encountered in MEMS, alcohols, which are not generally considered good lubricants, work.

Solubility in water is an important characteristic in lubricating MEMS. Water is always present in the air as humidity and the water does condense on surfaces. For some devices, like the air bag sensor, water is why these MEMS are used only once. These sensors have two tiny strips of material that come into contact upon rapid deceleration. Any water on the strip surfaces causes the strips to stick in the closed mode. Surface tension of the water holds the material together in the same way two panes of glass with water between become stuck. However, alcohol as a lubricant would prevent water from causing the strips to attach.

"It might also be possible to use a gas delivered liquid thin film that would regenerate the sensors allowing recycling of the air bag mechanisms," says Kim.

The researchers tested the gas lubricants at various vapor pressures and find that they produce a thin film across a wide range. The small size of the alcohol molecules allows them to coat fine details of the tiny machines and the presence of gas around the MEMS makes the system self-repairing. As the thin layer wears away, more lubricant condenses to heal the area. The thin films do not interfere with either mechanical or electrical operation.


"The next research issue we have is how to encapsulate the MEMS so we can entrap the gas," says Kim. "A variety of delivery methods exist including possibly using a polymer that emits the alcohol as temperatures increase."

The researchers also want to look at other alcohols and other compounds as potential MEMS lubricants.


The National Science Foundation and the Pennsylvania State University supported this work.

A’ndrea Elyse Messer | EurekAlert!
Further information:
http://www.psu.edu/

More articles from Process Engineering:

nachricht New manufacturing process for SiC power devices opens market to more competition
14.09.2017 | North Carolina State University

nachricht Quick, Precise, but not Cold
17.05.2017 | Fraunhofer-Institut für Lasertechnik ILT

All articles from Process Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>