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 Copper oxide photocathodes: laser experiment reveals location of efficiency loss
10.05.2019 | Helmholtz-Zentrum Berlin für Materialien und Energie

nachricht NIST research sparks new insights on laser welding
02.05.2019 | National Institute of Standards and Technology (NIST)

All articles from Process Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: The hidden structure of the periodic system

The well-known representation of chemical elements is just one example of how objects can be arranged and classified

The periodic table of elements that most chemistry books depict is only one special case. This tabular overview of the chemical elements, which goes back to...

Im Focus: MPSD team discovers light-induced ferroelectricity in strontium titanate

Light can be used not only to measure materials’ properties, but also to change them. Especially interesting are those cases in which the function of a material can be modified, such as its ability to conduct electricity or to store information in its magnetic state. A team led by Andrea Cavalleri from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg used terahertz frequency light pulses to transform a non-ferroelectric material into a ferroelectric one.

Ferroelectricity is a state in which the constituent lattice “looks” in one specific direction, forming a macroscopic electrical polarisation. The ability to...

Im Focus: Determining the Earth’s gravity field more accurately than ever before

Researchers at TU Graz calculate the most accurate gravity field determination of the Earth using 1.16 billion satellite measurements. This yields valuable knowledge for climate research.

The Earth’s gravity fluctuates from place to place. Geodesists use this phenomenon to observe geodynamic and climatological processes. Using...

Im Focus: Tube anemone has the largest animal mitochondrial genome ever sequenced

Discovery by Brazilian and US researchers could change the classification of two species, which appear more akin to jellyfish than was thought.

The tube anemone Isarachnanthus nocturnus is only 15 cm long but has the largest mitochondrial genome of any animal sequenced to date, with 80,923 base pairs....

Im Focus: Tiny light box opens new doors into the nanoworld

Researchers at Chalmers University of Technology, Sweden, have discovered a completely new way of capturing, amplifying and linking light to matter at the nanolevel. Using a tiny box, built from stacked atomically thin material, they have succeeded in creating a type of feedback loop in which light and matter become one. The discovery, which was recently published in Nature Nanotechnology, opens up new possibilities in the world of nanophotonics.

Photonics is concerned with various means of using light. Fibre-optic communication is an example of photonics, as is the technology behind photodetectors and...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

 
Latest News

Novel communications architecture for future ultra-high speed wireless networks

17.06.2019 | Information Technology

Climate Change in West Africa

17.06.2019 | Earth Sciences

Robotic fish to replace animal testing

17.06.2019 | Ecology, The Environment and Conservation

VideoLinks
Science & Research
Overview of more VideoLinks >>>