Bench Press

Having read and watched a fair amount of science fiction during my formative years, I’ve always been enamored with the concept of nanobots being used within the human body to help maintain our health. While the reality of microscopic machines moving to normally inaccessible areas of the human body and performing life saving tasks is still decades away, researchers led by Professor James Friend at Australia’s Monash University have demonstrated a proof of concept piezoelectric ultrasonic motor that could be a crucial step in providing locomotion for the nanosurgical robots of tomorrow.

In the abstract of their paper they describe their concept as:

A motor for in vivo microbot propulsion is presented with a stator diameter of 250 µm, demonstrating the potential to directly drive a flagellum for swimming at up to 1295 rpm with a torque of 13 nN m. The motor uses coupled axial-torsional vibration at 652–682 kHz in a helically cut structure excited by a thickness-polarized piezoelectric element.

Piezoelectric ultrasonic motors like the one designed by the team are built to harness special materials that exhibit the piezoelectric effect. Materials like lead zirconate titanate, thanks to the piezoelectric effect, are capable of producing electricity when stress is applied as well as the converse, producing stress when an electrical field is applied. This effect is already used in a variety of everyday applications, such as electric guitar pickups as well as auto-focus in reflex cameras. The motor (seen below), called the Proteus, designed by Friend’s team is made up of three main components: the piezoelectric element, the stator, and the rotor.

The team began to design the Proteus by utilizing computer models (seen below) to produce a novel robust stator design. They determined a helically cut stator would serve best in transferring stress and turning the rotor. The group hopes to improve their model in future work by incorporating further criteria and motor components.

After utilizing computer models to design the stator a prototype was fabricated for physical tests. Various tests were run to ascertain the potential of the Proteus. The group’s tests are promising as they found the “output power [is] on the order of what is necessary to navigate small human arteries.” In addition to the promising power output, the stator design is currently “70% smaller than the smallest design produced so far”.

While the design of a small motor is still just a small first step towards in vivo swimming surgical nanobot I can’t help but think about the possibilities this innovation will lead to. Maybe Professor Friend can contact Dr. Gracias at John Hopkins about working on a swimming microgripper next.

All graphics and quotes from:

B Watson, J Friend and L Yeo 2009. Piezoelectric ultrasonic resonant motor with stator diameter less than 250 µm: the Proteus motor. Journal of Micromechanics and Microengineering.