Manufacturing Bits: Sept. 4
SOI Prevents Dropped Calls
Tired of dropped calls or slow Internet service on cell phones?
One enabling technology is the development of more precise filter components. For example, Purdue University has devised a nanoelectromechanical resonator, based on silicon-on-insulator (SOI) technology.
Resonant nanoelectromechanical systems (NEMS) could be used in mass sensing, signal processing and field detection applications. The nanoresonators from Purdue were shown to control their vibration frequencies better than other resonators.
This image from a scanning electron microscope shows a tiny mechanical device, an electrostatically actuated nanoresonator, that might ease congestion over the airwaves to improve the performance of cell phones and other portable devices. (Purdue University image)
The key part of Purdue’s device is a silicon beam, which is attached at two ends. The beam, which vibrates in the center, has a 130nm feature size. Applying a current to the beam causes it to vibrate side-to-side or up and down. The beam can be adjusted or tuned.
These devices are made on an SOI substrate using a top-down fabrication technique. It can be integrated with CMOS transistors, enabling the development of devices with highly tunable, nonlinear frequency response characteristics.
“We are not inventing a new technology, we are making them using a process that’s amenable to large-scale fabrication, which overcomes one of the biggest obstacles to the widespread commercial use of these devices,” said Jeffrey Rhoads, an associate professor of mechanical engineering at Purdue University.
The new SOI resonators could provide higher performance than current components and MEMS systems. “It is very difficult to make a good tunable filter with transistors, inductors and other electronic components, but a simple nanomechanical resonator can do the job with much better performance and at a fraction of the power,” said Saeed Mohammadi, an associate professor of electrical and computer engineering at Purdue.
“Because the devices are tiny and the fabrication has almost a 100 percent yield, we can pack millions of these devices in a small chip if we need to,” Mohammadi said. “It’s too early to know exactly how these will find application in computing, but since we can make these tiny mechanical devices as easily as transistors, we should be able to mix and match them with each other and also with transistors in order to achieve specific functions. Not only can you put them side-by-side with standard computer and electronic chips, but they tend to work with near 100 percent reliability.”
SOI Enables Flexible Electronics
Wayne State University has developed a SOI technology for use in making flexible electronic products.
Researchers from Wayne State have fabricated CMOS circuits onto SOI wafers. They also incorporate two layers of a polymer called Parylene C. One of the layers is perforated in order to bond it to a flexible substrate.
The parylene layer is use to protect the substrate from environmental moisture. Parylene is the trade name for a variety of chemical vapor deposited poly(p-xylylene) polymers.
“The ultimate goal is to develop flexible and stretchable systems integrated with electronics, sensors, microfluidics, and power sources, which will have a profound impact on personalized medicine, telemedicine and health care delivery,” said Yong Xu, associate professor of electrical and computer engineering in the College of Engineering at Wayne State.
The technology could result in retinal prostheses. Other applications include balloon catheters, stents and other products.
Researchers Devise Twisted Lasers
The University of Liverpool has developed new technique for laser micro-machining for use in semiconductor, industrial and medical applications.
Typically, lasers have linear polarizations, where the beam is vertical. Using twisted wave-fronts to transform the electric field, Liverpool has devised a laser with radial and azimuthal polarizations. In this technology, there is a directional change of the electric field.
Researchers used a 100 femtosecond-pulse laser source and a spatial light modulator in order to change the polarization. “This technology and these new modes of polarization enabled us to achieve significant gains in processing speed and quality,” said Olivier Allegre, who is in the School of Engineering at Liverpool University.
The team used twisted wave-fronts to transform the electric field. Source: University of Liverpool.
“We will now study how this new technique could improve the processing of various materials, such as semiconductors and dielectrics. The technique is also significant for improving image detail in microscopy, and could benefit fluorescence-based imaging of biological samples,” he added.
Tags: nanomechanicalelectrical systems, NEMS, Purdue University, SOI, twisted lasers, University of Liverpool, Wayne State