A technique for manufacturing microscale machines may enable creation of machines with three-dimensional, freely moving parts.

These machines---implantable microelectromechanical systems (iMEMS)--are constructed using biocompatible hydrogels. They can be fine-tuned to perform a wide range of functions, and are wirelessly controllable.

iMEMS magnetic drive mechanism. Credit: Sia Lab/Columbia UniversityThe manufacturing technique addresses several basic considerations for these devices, developers say. The moveable components have to be biocompatible, rather than the usual less-compatible silicon. The power source cannot be a toxic battery. And communications with the device must be wireless and must work without an implanted battery. (Watch a video.)

Sam Sia of Columbia University’s College of Engineering in New York led a team that addressed these requirements. To form their test machines, the team polymerized sheets of hydrogel and incorporated a stepper mechanism to control the z-axis. By polymerizing one layer at a time and controlling the z-axis, they were able to include complex composite structures in individual layers. Structures that needed more stiffness, such as gears, required the researchers to fine-tune the polymerization and assembly process.

Magnetism, a non-toxic power source, solved the second and third requirements. Magnetic iron particles incorporated in the hydrogel sheets power moving parts and provide control.

Working with Francis Lee, a Columbia orthopedic surgeon, the team ran a proof-of-concept test. An iMEMS device delivered chemotherapy adjacent to the cancerous tumor, limiting tumor growth with one-tenth the toxicity of traditional chemotherapy.

Sia foresees multiple medical applications of these machines, in addition to drug delivery systems. Potential uses include catheters, pacemakers, and soft robotics.