Super-thin membranes clear the way for chip-sized pumps

October 28, 2013

The ability to shrink laboratory-scale processes to automated chip-sized systems would revolutionize biotechnology and medicine. For example, inexpensive and highly portable devices that process blood samples to detect biological agents such as anthrax are needed by the U.S. military and for homeland security efforts. One of the challenges of "lab-on-a-chip" technology is the need for miniaturized pumps to move solutions through micro-channels. Electroosmotic pumps (EOPs), devices in which fluids appear to magically move through porous media in the presence of an electric field, are ideal because they can be readily miniaturized. EOPs however, require bulky, external power sources, which defeats the concept of portability. But a super-thin silicon membrane developed at the University of Rochester could now make it possible to drastically shrink the power source, paving the way for diagnostic devices the size of a credit card.

"Up until now, electroosmotic pumps have had to operate at a very high voltage--about 10 kilovolts," said James McGrath, associate professor of biomedical engineering. "Our device works in the range of one-quarter of a volt, which means it can be integrated into devices and powered with small batteries."

McGrath's research paper is being published this week by the journal Proceedings of the National Academy of Sciences.

McGrath and his team use porous nanocrystalline silicon (pnc-Si) membranes that are microscopically thin--it takes more than one thousand stacked on top of each other to equal the width of a human hair. And that's what allows for a low-voltage system.

A porous membrane needs to be placed between two electrodes in order to create what's known as electroosmotic flow, which occurs when an electric field interacts with ions on a charged surface, causing fluids to move through channels. The membranes previously used in EOPs have resulted in a significant voltage drop between the electrodes, forcing engineers to begin with bulky, high-voltage power sources. The thin pnc Si membranes allow the electrodes to be placed much closer to each other, creating a much stronger electric field with a much smaller drop in voltage. As a result, a smaller power source is needed.

"Up until now, not everything associated with miniature pumps was miniaturized," said McGrath. "Our device opens the door for a tremendous number of applications."

Along with medical applications, it's been suggested that EOPs could be used to cool electronic devices. As electronic devices get smaller, components are packed more tightly, making it easier for the devices to overheat. With miniature power supplies, it may be possible to use EOPs to help cool laptops and other portable electronic devices.

McGrath said there's one other benefit to the silicon membranes. "Due to scalable fabrication methods, the nanocrystalline silicon membranes are inexpensive to make and can be easily integrated on silicon or silica-based microfluid chips."
-end-


University of Rochester

Related Silicon Articles from Brightsurf:

Single photons from a silicon chip
Quantum technology holds great promise: Quantum computers are expected to revolutionize database searches, AI systems, and computational simulations.

For solar boom, scrap silicon for this promising mineral
Cornell University engineers have found that photovoltaic wafers in solar panels with all-perovskite structures outperform photovoltaic cells made from state-of-the-art crystalline silicon, as well as perovskite-silicon tandem cells, which are stacked pancake-style cells that absorb light better.

Surprisingly strong and deformable silicon
Researchers at ETH have shown that tiny objects can be made from silicon that are much more deformable and stronger than previously thought.

A leap in using silicon for battery anodes
Scientists have come up with a novel way to use silicon as an energy storage ingredient.

Flexible thinking on silicon solar cells
Combining silicon with a highly elastic polymer backing produces solar cells that have record-breaking stretchability and high efficiency.

No storm in a teacup -- it's a cyclone on a silicon chip
University of Queensland researchers have combined quantum liquids and silicon-chip technology to study turbulence for the first time, opening the door to new navigation technologies and improved understanding of the turbulent dynamics of cyclones and other extreme weather.

Black silicon can help detect explosives
Scientists from Far Eastern Federal University (FEFU), Far Eastern Branch of the Russian Academy of Sciences, Swinburne University of Technology, and Melbourne Center for Nanofabrication developed an ultrasensitive detector based on black silicon.

2D antimony holds promise for post-silicon electronics
Researchers in the Cockrell School of Engineering are searching for alternative materials to silicon with semiconducting properties that could form the basis for an alternative chip.

Silicon technology boost with graphene and 2D materials
In a review published in Nature, ICFO researchers and collaborators report on the current state, challenges, opportunities of graphene and 2D material integration in Silicon technology.

Light and sound in silicon chips: The slower the better
Acoustics is a missing dimension in silicon chips because acoustics can complete specific tasks that are difficult to do with electronics and optics alone.

Read More: Silicon News and Silicon Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.