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12/14/2014 MicroWindmills: From Lab to Market
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MicroWindmills: From Lab to Market
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Tue, 12/09/2014 4:40pm
by Meaghan Ziemba, Editor, @MZiembaWDD
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Microwindmill, energy harvesting platforms help make sensorsmore power independent.Not all design engineering ideas begin as sketches on a restaurant napkin. Some designs start inthe labs at the most prestigious engineering schools around the world, such is the story of JungChih (J.C.) Chiao and Smitha Rao’s microwindmill that generates wind energy.
More than 11 years ago, Chiao, an electrical engineering professor at the University of Texas inArlington, was focusing his research on microelectromechanical systems (MEMS), when he andRao had the idea of putting something moveable, like a windmill, on silicon chips.
“There were obvious reasons to do this,” says Chiao. “One was energy harvesting, because inmost computers and electronics there is a lot of heat gradient, and we thought maybe we coulduse the design to harvest the airflow in the module system.
We could then take that harvested energy and use it as a fan to cool down the system like acomputer cooling fan, but much smaller and more efficient.”
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Microwindmills have the potential to be charging platforms to provide power in areasthat it is not available. Photo Credit: University of Texas, Arlington
The team was usingconventional silicon MEMSfabrication techniques, sothe silicon layer ended upbeing very thin. “Silicon is avery strong material, but atthe same time, it’s verybrittle with a micrometerthickness,” explains Chiao.“Anytime there was a verylight wind, the wind turbineoperated fine, but when thewind speed picked up, thesilicon couldn’t take theforce and shattered.”
After several trials with nosuccess, Chiao admitted thatthe team sort of gave up anddidn’t revisit the idea until2012 when they connectedwith Taiwanbased, companyWinMEMS.
Back from the DeadThe WinMEMS CEO was a former classmate of Chiao’s, and after a class reunion, he explained toChiao that he thought they could work together. WinMEMS uses different materials, such as nickelalloy, to create MEMS devices. Chiao explained how they started making very small surgical tools,micro gears, and micro inductors using WinMEMS’ fabrication process. “It wasn’t until the end ofthe design process for that project that my research associate, Rao, suggested we revisit thewindmill idea using the materials from WinMEMS.”
No available literature or tools existed to help start the design process because WinMEMS’fabrication procedures have not been standardized with respect to design rules, layout functions,and building blocks. Chiao and Rao only had intuition from the past twelve years of experience tohelp guide them through the design process.
“We had to think about how to make the blades moveable while keeping the main structure stableand robust while the wafers pass through harsh chemical and mechanical processes. We usedmicromachining techniques with sacrificial layers to create a 3D structure from several platedlayers of nickel alloy,” says Chiao. “In laymen’s terms, it’s like making a cake. We had fivestructural layers with four sacrificial layers in between. When the entire wafer was done withdeposition, we soaked it in an etchant solution remove the sacrificial layers. 3D hinges andinterconnects were formed to allow mechanical motion. There is no assembly required.”
This particular technique is new, but the basic principles are exactly the same as in MEMSfabrication, providing the advantages of low cost, mass production, waferscale batch
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manufacturing, and integration with complementary metal–oxide–semiconductor (CMOS) circuitry.However no commercial software has adopted this particular technique, Chiao and his team had towork from layers of 2D drawings, visualizing what it would look like in the 3D world.
“WinMEMS has developed devices used for integrated circuit probes that have displayedrobustness, owning to mechanical elasticity in the alloy,” says Chiao. “In general, it has not beenstatistically demonstrated that it can be used for a long period of time in regards to the MEMSfields, so that is what we are focusing on now.”
Research That Has Never Been Done BeforeChiao and his team faced various challenges when designing microwindmills, however they viewthem as research opportunities. First, the idea stems from research on something that has neverbeen done before – no standards to consider, or previous designs to reference.
From a design perspective, this process is new to MEMS engineers, so there are no design orsimulation tools to help with the fabrication process. The microwindmills also involve electricaland mechanical design, so the team had to create a new modeling tool that would incorporateboth.
“The second main challenge is the physics within the micro scale structures, the knowledge wehave on large windmills does directly apply to what we’re trying to do. For example, in a biggerwindmills, we wouldn’t care too much about dust.
However, in a microwindmill, dust could ruin the smaller parts,” says Chiao. “The deformation ofblades from pressure in bigger windmills is also a lot different in microwindmills, so we need tofind solutions to these types of issues.”
The third challenge that the team faces is application. Chiao believes that the research will enableideas for many different applications in wireless sensors for the Internet of Things, because thesensors can be placed at remote locations communicating with the Cloud with selfsustainingpower. “If we invent just one thing for one particular application, then that’s not a very goodinvestment of our research in the university,” says Chiao.
Other challenges involve the researchers thinking about issues that they normally would notconsider, such as mass production and cost. Chiao claims that the team is not solving theseparticular issues in a traditional fashion. “Traditionally, cost issues would be solved by looking atdetails in the manufacturing processes. We don’t really know what the manufacturing processeswill be for these types of devices in the future, so we implement device architectures with onlymassproducible batch fabrication in the front end.” For example, the team is trying to keep thedesign simple while maintaining an optimal performance level, which presents yet anotherobstacle.
In a conventional design of a windmill, the hinge is a small portion because the blade takes upmost of the space. At the microscale, the blade has to be small, which means the hinge needs tobe even smaller. When the windmill interacts with wind, there is debris, dust, and moisture in theair. The moisture can create stiction, which is when the water molecules start to become glue,binding the materials together. This may be resolved with some sort of lubricant, but according to
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Chiao, the lubricant for metal MEMS devices could be completely different from what is being usedin larger ones.
Commercial PotentialChiao’s team anticipates a lot of commercial potential for their idea, including a charging platformfor energy harvesting to provide power in areas that it is not available. They also believe it couldbe used to power wireless sensors in monitoring systems for bridges, highways, and buildings.
“Right now the United States is facing an infrastructure problem, and one structure requires ahundred or more sensors to monitor the environmental issues. It’s not a good idea to sendsomeone once a year to replace all the batteries within all the sensors,” says Chiao. “This microwindmill, energy harvesting platform would make the sensor more power independent by allowingit to continuously operate. This is also an enabler for wireless sensors used for the Internet ofThings. Imagine millions of wireless sensors that can be independently placed in remote locations,around cities, and around us to communicate with the cloud so we can quickly assess theenvironments, disaster scenarios, or infrastructure health by getting a more complete picturefrom a big data network.”
Since their announcement, Chiao has received a lot of responses for potential applications.Several companies have approached them with ideas, and they have even gained internationalrecognition from Germany, Taiwan, and Korea.
“The idea can also be applied to different industries, such as computers, portable electronics,sensors, and automotive,” says Chiao. “People see the potential and like to know more.”
According to Chiao, his goal is to try and establish a platform that will inspire interesteverywhere.
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• Reply •
Bob G • 4 days ago
Sounds like another scam similar to sweat batteries or RF harvesting, probably generatingpower in the useless subfemtowatt range. Should the article not include some specificsregarding actual or predicted performance?
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• Reply •
The Old Soldering Gunslinger • 4 days ago
Hmmm...w=0.625 A (v cubed) where w= Watts, 0.625 is a constant based upon standard airdensity(15 degrees C at Sea Level), A= the area of the rotor in square meters and v= windvelocity in meters / secondPerhaps femtoWatts is a bit optimistic...but a whold bunch of femtowatt wind generators canbecome...perhaps...whole watts!I remain,The Old Soldering Gunslinger
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