No one ever gets anywhere by setting the bar low — so it's exciting to see that researchers are dreaming big when it comes to the next class of medical devices. Actually, they're tackling two challenges at once: devices that are not only tiny, but also self-powered. Just as Hollywood challenges its stars to be triple threats (singing, dancing, and acting), the medical industry is increasingly challenging its devices to be double threats: small and self-powered. Take a look at two examples that offer glimpses of the future of self-propelled, miniature medical devices that could open doors for everything from targeted drug delivery to minimally invasive surgery.
Engineers at the University of California, San Diego , are developing a nanomotor, also dubbed a "microrocket," that can propel itself through acidic environments such as the human stomach. In acidic environments, the microrocket spontaneously produces bubbles of hydrogen gas, which propels it to move farther than 100 times its 0.0004-inch length in just one second. The interior is lined with zinc, which is more biocompatible and "greener" than other materials, and leads to the generation of the hydrogen bubbles. The team also developed a version with a magnetic layer, enabling them to better guide the movement of the microrockets toward desired locations in the body. The nanomotors could hold applications in targeted drug delivery or diagnostic imaging.
Although implantable medical devices have been around for a long time, developing a lasting, self-powered implantable device that eliminates the need for cumbersome batteries or wires remains a challenge. Ada Poon, an assistant professor at the Stanford School of Engineering , is developing a class of self-propelled medical devices that can be implanted or injected into the human body and powered wirelessly using electromagnetic radio waves.
One key to her progress has been an unconventional way of viewing the conductivity of human tissue. Scientists who have long been working on models of how high-frequency radio waves travel through human tissue have assumed that human muscle, fat, and bone were generally good conductors of electricity. However, Poon realized that since human tissue is actually a poor conductor of electricity, it can be viewed as a dielectric — a type of insulator. In a dielectric, the signal is conveyed as waves of shifting polarization of atoms within cells. Since it is a "low-loss" dielectric, little of the signal gets lost along the way. This revelation was what led Poon to develop an antennae for the medical device that could be 100 times smaller and deliver the same power as previous attempts; it is just two millimeters square, small enough to travel through the bloodstream.
Although much progress undoubtedly lies ahead for researchers on the forefront of this technology, it's getting easier than ever to envision that the medical devices of the future will not only be smaller, but also more energy-efficient than ever before.
