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 Intelligent wheelchairs, predictive prostheses
20.12.2017 | Fraunhofer-Institut für Produktionstechnik und Automatisierung IPA

nachricht Jelly with memory – predicting the leveling of com-mercial paints
15.12.2017 | Fraunhofer-Institut für Produktionstechnik und Automatisierung IPA

All articles from Process Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Polymers Based on Boron?

18.01.2018 | Life Sciences

Bioengineered soft microfibers improve T-cell production

18.01.2018 | Life Sciences

World’s oldest known oxygen oasis discovered

18.01.2018 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>