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Improved microfluidic channels in MEMS devices are playing a key role in the next generation of biomedical applications, according to Abe Lee, a professor at the Center for Biomedical Engineering at the University of California, Irvine.
New advances in silicon and other materials have brought forth much better and tinier microchannels for fluid applications.
Lee sees these advances as closing the loop between in vitro (test tube) diagnostics and in vivo (inside the body) therapies for medical problems using microfluidic drug-delivery systems.
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A microfluidic channel is a structure fabricated in silicon, glass, or polymer on a chip. It allows the flow of liquids and gases that can be manipulated and controlled through valves and switches. This is instrumental in sample preparation, detection, analysis and delivery of a wide range of drugs in point-of-care, patient-monitoring and therapeutic applications. It is also key to the advancement of minimally invasive therapy, precision surgery and biosensing.
Lee’s optimism is not without some impressive market projections, though some are more bullish than others. For example, UBS Warburg LLC forecasts a $28.8 billion U.S. market for drug delivery by 2005, up from $14.4 billion in 2000, a compound annual growth rate of about 17 percent.
The European microsystems organization NEXUS estimates a $10 billion worldwide market for bioMEMS by next year. NEXUS worked with Roger Grace, a MEMS market expert, to produce a June 2000 market study that forecast a major market growth area for medical/biomedical MEMS that will grow at a compound annual rate of 32.5 percent.
The idea of microfluidic channels in silicon has been around for more than two decades but only recently have rapid gains been made in understanding and improving these channels thanks largely to biomedical applications.
Microfluidics are playing a role in diagnosing and treating a number of diseases and conditions:
Cancer
Cancer is a costly disease with a large market potential for microfluidic analysis and drug-treatment systems. John Santini Jr., president and chief scientific officer at MicroCHIPS Inc., of Cambridge, Mass., estimates worldwide drug sales for cancer therapy alone at $31 billion in 2004, up from $20 billion in 1999. His firm is developing an implantable bioMEMS drug-delivery system.
Carl Grove, president of iMEDD Inc., Columbus, Ohio, said drug sales for just cancer chemotherapy account for $20 billion annually. He described a proprietary microengineered drug-delivery product iMEDD is working on. And Lee is developing microfluidic brain microcontrols, which it has now licensed to Target Therapeutics of Fremont, Calif., for the in-vivo treatment of inoperable brain tumors.
At the Lawrence Livermore National Laboratory in California, a microfluidic programmable processor is under development for both in-vivo and in-vitro treatment of cancer. The MD Anderson Cancer Center is the lead member on this DARPA-sponsored effort.
Coronary diseases
Professor Michael Reed at the University of Virginia’s Department of Electrical and Computer Engineering in Charlottesville, sees a worldwide market for coronary stents of $5 billion by 2005, up from $2 billion last year.
Stents are implanted in more than 80 percent of patients with coronary atherosclerosis. Some 30-50 percent of these stents, over time, typically suffer from scar tissue growth, which forces the stent to close and restrict blood flow in the arteries.
Reed hopes to integrate microprobes in microfluidic packages to pierce, in-vivo, compressed artery plaque. His approach is said to have longer-term efficacy than present local drug-delivery means, which are limited to seven to 28 days. He’s working on this project with the Pittsburgh Vascular Institute, Carnegie Mellon University, GE Medical Systems, the University of Texas at San Antonio, and Setagon Inc.
The brain
Integrating microfluidics with other devices like valves, pumps, switches, relays and microprocessors will reduce the end cost of biomedical analysis systems and provide higher-quality patient care. Applications such as mimicking the signaling of neural synapses on a single silicon will become possible, leading to a better understanding of the human brain and neural system. In fact, Lee foresees the access of MEMS and later nanotechnologies to the human brain as “the last frontier” of biomedical science.
Professor Ken Wise, of the University of Michigan’s department of electrical engineering and computer science, is putting his world-renowned neural-implant experience to use to develop dense recording/stimulating electrode array probes for building an in-vivo electronic interface to the brain. The project is one of two test beds at the school’s Engineering Research Center and is being supported by Cochlear Corp., of Englewood, Colo., and Advanced Bionics, of Sylmar, Calif.
The probes can deliver drugs at the cellular level using microfluidic channels. Integrated on each probe is a complete closed-loop fluidic control system, including flow meters, microvalves, and micropumps. The flow meters have been demonstrated and the valves and pumps are still in development.
A few more years
But no matter how optimistically researchers view their work, they caution that it will take at least a few more years to bear fruit commercially. They predict that future miniaturized fluidic channels and reservoirs will feature high surface-to-volume ratios that will allow fluidic reactions to increase in speed. This will reduce the cost of chemical reagents and the levels of power consumption needed for processing different liquids. More precise mixing and dosing of drugs will also result.
Many of the microfluidic systems in development will work inside catheters. Catheter-based integrated microfluidic systems can provide a big boost to reducing health care costs by eliminating stroke recovery times. The cost for treating strokes and rehabilitating patients presently accounts for more than $30 billion a year in the United States according to Lee.
“Microfluidics is a platform with the potential that parallels electronics” he says. He predicts bioMEMS will close the loop between patient diagnostics and treatment. “Biotechnology will require microfluidics platforms to monitor and control cellular machinery and their functions” he added.
He cautioned that for all of this to occur, “we need to train a new breed of researchers capable of crossing the bio/info/nano/boundaries.”