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 Diamond watch components
18.06.2018 | Schweizerischer Nationalfonds SNF

nachricht Quick and safe laser joining of steel-aluminum mixed connections
05.06.2018 | Laser Zentrum Hannover e.V.

All articles from Process Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: Temperature-controlled fiber-optic light source with liquid core

In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.

Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Better model of water under extreme conditions could aid understanding of Earth's mantle

21.06.2018 | Earth Sciences

What are the effects of coral reef marine protected areas?

21.06.2018 | Life Sciences

The Janus head of the South Asian monsoon

21.06.2018 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>