Micro-origami: Researchers fold up micrometer-scale 'voxels' for drug delivery

Researchers at the USC Information Sciences Institute have demonstrated a way to manufacture miniscule closed containers that might be used to deliver precise micro- or even nano-quantities of drugs.

According to ISI project leader Peter Will, who is also a research professor in the Viterbi School of Engineering, the new technique, described in a paper in the Journal of Micromechanics and Microengineering, is a two-step process.

Part one is the creation of flat patterns, origami, of exactly the fold up shapes familiar to kindergarten children making paper pyramids, cubes or other solids, except that these are as small 40 micrometers (µm) on a side. (1 inch = 25,400 µm)

Instead of paper, the USC researchers created the patterns in polysilicon sitting on top of a thin film of gold, using a well-established commercial silicon wafer process called PolyMUMPs. The next step was clearing the polysilicon off the hinge areas by etching.

When the blanks were later electrocoated with permalloy to make them magnetic, the photomask used left hinge areas uncoated, to make sure they were the places that folded.

Then the folding had to be accomplished. First the researchers bent the hinges by application of magnetic force to the permalloy. Water pressure and capillary forces generated by submerging the tiny blanks in water, and drying them off did the final folding into shape.

The experiments spend considerable time comparing various methods of controlling the closure effects of water drying with simple flaps designed to close over each other to form "envelops," the directing water from different directions sequence the closing. Varying the time of trying could produce tighter seams.

"Our experiments show" says the paper, that "the combination of partial folding of structures by magnetic actuation and liquid closure to bring the structures to their final closed state is an extremely promising technique for mass production of large arrays of micrometer size …voxels. Furthermore, we believe that future optimization of the voxel hinge geometry and composition should allow for extensions of our work to" much smaller voxels.

The Voxel team - consisting of Will, professor of chemistry Bruce Koel (who has since gone to Lehigh University), former post-doctoral researcher Alejandro Bugacov and former grad student (now graduate) Rob Gagler folded a number of different shapes, including four- and five-sided pyramids, pentagonal 'lotus' shapes, and also simple square plates that folded over each other to make flat mini-envelopes.

Will has been pursuing the idea of creating voxels for many years, "way back to my days in HP labs, when I was working in Medical and Chemical applications." The USC team designed the chips using MEMSPRO CAD software; the actual chip fabrication was done in France.

"The experimental work was done on campus," said Will, "since ISI doesn't have a wet lab."

The paper is "Voxels: volume-enclosing microstructures," J. Micromech. Microeng. 18 (2008) 055025.

Source: University of Southern California

Related stories:

Organizing an Earth Systems Science Agency
In an article published today in the journal Science, a group of former senior federal officials call for the establishment of an independent Earth Systems Science Agency (ESSA) to meet the unprecedented environmental and economic challenges facing the nation. They propose forming the new agency by merging the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Geological Survey (USGS).
New findings show a slow recovery from extreme global warming episode 55 million years ago
Most of the excess carbon dioxide pouring into the atmosphere from the burning of fossil fuels will ultimately be absorbed by the oceans, but it will take about 100,000 years. That is how long it took for ocean chemistry to recover from a massive input of carbon dioxide 55 million years ago, according to a study published this week in the journal Science.
At 2.8 km down, a 1-of-a-kind microorganism lives all alone
The first ecosystem ever found having only a single biological species has been discovered 2.8 kilometers (1.74 miles) beneath the surface of the earth in the Mponeng gold mine near Johannesburg, South Africa. There the rod-shaped bacterium Desulforudis audaxviator exists in complete isolation, total darkness, a lack of oxygen, and 60-degree-Celsius heat (140 degrees Fahrenheit).
Ripple effect: Water snails offer new propulsion possibilities
(PhysOrg.com) -- A UC San Diego engineer has revealed a new mode of propulsion based on how water snails create ripples of slime to crawl upside down beneath the surface.
'Fingerprinting' method tracks mercury emissions from coal
(PhysOrg.com) -- University of Michigan researchers have developed a new tool that uses natural "fingerprints" in coal to track down sources of mercury polluting the environment. The research is published in today's online issue of the journal Environmental Science & Technology.
Preserved by ice: Glacial dams helped prevent erosion of Tibetan plateau
The Tsangpo River is the highest major river in the world, starting at 14,500 feet elevation and plunging to the Bay of Bengal, scouring huge amounts of rock and soil along the way. Yet in its upper reaches, the powerful Tsangpo seems to have had little effect on the elevation of the Tibetan Plateau.
Circadian clock may be critical for remembering what you learn
(PhysOrg.com) -- The circadian rhythm that quietly pulses inside us all, guiding our daily cycle from sleep to wakefulness and back to sleep again, may be doing much more than just that simple metronomic task, according to Stanford researchers.
'Deadly dozen' reports diseases worsened by climate change
Health experts from the Wildlife Conservation Society today released a report that lists 12 pathogens that could spread into new regions as a result of climate change, with potential impacts to both human and wildlife health and global economies. Called The Deadly Dozen: Wildlife Diseases in the Age of Climate Change, the new report provides examples of diseases that could spread as a result of changes in temperatures and precipitation levels. The best defense, according to the report's authors, is a good offense in the form of wildlife monitoring to detect how these diseases are moving so health professionals can learn and prepare to mitigate their impact.

News discussion:

Technology news