July 26, 2006

Engineers’ New Process Revolutionizes Micro Medical Devices

  — Research opens door to new dimension in customization and mass production of tiny medical devices for drug delivery

Using this micropositioning system to manipulate a laser, Dr. Yuan-Shin Lee and Dr. Roger Narayan are able to create a three-dimensional microstructure such as a microneedle. (Photo: Jennifer Weston)

Imagine a world in which tiny devices can cure diseases and correct defects in the human body. That’s the goal of research being conducted by engineering researchers at North Carolina State University and the University of North Carolina at Chapel Hill (UNC-CH). They are designing novel applications of microstructures and nanostructures to create medical devices that may one day revolutionize human medicine.

Dr. Roger Narayan, associate professor of biomedical engineering in the joint Department of Biomedical Engineering at NC State and UNC-CH, in collaboration with researchers at Laser Zentrum Hannover in Germany, developed a two photon polymerization (2PIP) process to produce three-dimensional microstructured medical devices using Ormocer®, an organic-inorganic hybrid material currently used in dentistry. The process opens new possibilities for micro and nano devices that are customized for specific biomedical purposes.

Once the new process was developed, the researchers contacted Dr. Yuan-Shin Lee, professor of industrial and systems engineering at NC State, who is internationally recognized as a pioneer in the field of computational design and manufacturing. Lee’s modeling work uses computer-aided molecular modeling and molecular design to create optimal specifications for each tiny device according to its specific use. He has developed a new modeling and design process that allows the researchers to test the limits of the hybrid materials by varying the structure of the devices and changing the elasticity along a greater range.

“Modeling at the molecular level represents a new dimension of modeling and analysis,” said Lee. “Since the physical properties of materials at the microscale are very different from the physical properties at the macroscale, we must design a modeling process that is highly specific. Using molecular modeling and computer-aided molecular design, we can manipulate the material properties to optimize performance.”

Currently the team is working to design and produce microneedles with a variety of specifications and modeling the penetration of the needles in skin to improve geometry and design. The designs are being tested and validated in the Biomechanics Laboratory at NC State with the help of Dr. Peter Mente, assistant professor of biomedical engineering.

The two photon induced polymerization (2PIP) process can produce these microneedles using Ormocer®. (Figures courtesy Dr. Roger Narayan)

“The conventional microneedles are not mass producible,” says Narayan. “What we are able to do is produce needles with unique geometrics tailored with optimal skin penetration and fracture resistance properties. Our goal is to be able to customize and mass-produce these microneedles. Dr. Lee’s modeling work will help us find the most efficient and effective way to manufacture the devices using this new laser technique.”

In the 2PIP process laser pulses are delivered in femtosecond (one millionth of a nanosecond) pulses to break chemical bonds on photoinitiator molecules. These molecules react with the Ormocer® monomers to create radicalized polymolecules. (Monomers are single molecules that have the ability to combine with similar molecules in a process called polymerization.) The lasers are manipulated in three dimensions using a micropositioning system to create a three-dimensional microstructure such as a microneedle. This new process opens the doors for the development of nano and micro devices that will have a wide variety of applications from painless injections to orthopedic, prosthetic and cardiovascular devices.

“What initially attracted me to this type of research is the possibility that we may someday have tiny machines that can function within the human body to repair and heal the body,” said Lee. “There is beauty in the machine that can do what your hands cannot do and see what your eyes cannot see. This is the direction I see that engineering should go.”

Lee’s vision of a micromachine that heals or helps the human body may not be that far-fetched. He and Narayan already envision that their modeling and fabrication process may one day develop a tiny device that can reside in the body of a diabetic and not only monitor blood sugar levels but also deliver proper doses of insulin. The device would combine the microneedles they are currently designing with a microelectromechanical system (MEMS) and a nanosensor that remains viable in the human body. Essentially the diabetic would no longer have to prick a finger, inject insulin or wear an external insulin pump. Materials with antimicrobial properties may be incorporated so that the risk of infection, a serious concern for diabetics, would be all but eliminated.

“The tiny system that can go inside the body and make repairs will probably not be developed in my lifetime,” says Lee. “But it is satisfying to know that we are working in that direction.”

— weston —

Technical contacts:
Dr. Yuan-Shin Lee, (919) 515-7195, yslee@ncsu.edu
Dr. Roger Narayan, (919) 696-8488, roger_narayan@unc.edu

Media contact:
Jennifer Weston, (919) 515-3848, weston@ncsu.edu

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