As a biomedical engineering student at Brown University, Sangeeta Bhatia often walked past the medical school's Artificial Organs Laboratory. One day in 1989 she knocked on the door and boldly asked if she could work there.

"I was interested in the idea that you could engineer organs," says Bhatia, who would later become a highly regarded innovator in tissue engineering, biomedical microdevices, and nanobiotechnology. "I told them, 'I'm small, I won't take up much room!'" Her energy and enthusiasm were persuasive, and the lab's director invited her to work there for the summer.

That early experience working in a research lab made a lasting impression on Bhatia. After graduating from Brown, Bhatia set her sights on earning a Ph.D. degree—a necessary requisite for the kind of job she wanted as a tissue engineer. She enrolled in the joint Harvard-MIT Health Sciences Technology graduate program, and she soon became intrigued by the considerable hurdles facing scientists who were trying to grow liver cells in the lab. At the same time, she was taking courses at Harvard Medical School. "I fell in love with the human body," she remembers. "I decided I wanted to finish the medical degree as well."

Bhatia now directs the Laboratory for Multiscale Regenerative Technologies at the Massachusetts Institute of Technology, where she is a professor of electrical engineering and computer science and of health sciences and technology, and is a biomedical engineer in the department of medicine at Brigham and Women's Hospital.

For years, many labs have tried to grow liver cells. Bhatia painstakingly figured out that one reason the liver cells did not thrive was because they were not in the right microenvironment. For example, they were missing contact with their neighboring cells. With that new knowledge in hand, she and her colleagues set about designing novel ways to provide liver cells in the laboratory with the critical factors they need to survive.

One of her long-term goals is to generate a complete implantable liver. Bhatia and her colleagues have designed tools—based on miniaturization methods used in making semiconductors—that they have used to create tiny colonies of human liver cells that model aspects of the full-size human organ. Through a process known as micropatterning, the bioengineers use a stencil to "print" liver cells onto glass in tiny islands, each 500 micrometers (millionths of a meter) in diameter. They surround each island of liver cells with supporting cells, providing a balance of "self" and "nonself" neighbors. The miniature livers can survive for up to six weeks and carry out the multiple functions of the natural organ, such as secreting albumin, transporting bile, and producing enzymes that metabolize toxins.

Practical applications are already emerging. "We think we can use human liver tissues to study whether a drug will be toxic in patients," she says. A test-drive showed that the system correctly flagged a number of drugs that were known to be toxic to the liver. This shortcut could reduce the costs of drug development and yield safer drugs, says Bhatia. Lately, Bhatia is particularly interested in using liver cell cultures to test live attenuated vaccines to ensure that they do not create a risk of causing disease.

Another major effort in Bhatia's lab is the development of nanoparticles designed to diagnose and treat cancer. One strategy makes use of nanoparticles that can sneak into blood vessels that feed tumors and then merge in clumps large enough to be detected by magnetic resonance imaging scans and reveal fast-growing cancer "hot spots."

Longer term, Bhatia envisions novel cancer treatments. In one scenario, nanoparticles would enter the patient's circulation, assemble themselves into tiny drug-dispensing machines, and then travel to tumors where physicians would trigger them by remote control to release their cancer-fighting payloads. Some of her recent research includes creating "nanorods" made of gold that can be targeted to tumors and heated by infrared light to kill cancer cells.

The stream of ideas seems endless. "They come to me at funny times and in unpredictable places," says Bhatia, who nevertheless says she spends a lot of time being "a regular person" with her two little girls, a book group, yoga, and lots of support from her scientist husband and nearby parents. She's also involved in mentoring and efforts to bring more women into the engineering field. "I'll say one thing—I'm never bored!"