3D printing technology is still under rapid development and we often see exciting new breakthroughs. Headlines sometimes announce material advancements, but the vast majority of 3D-printed objects are still plastic. Those are almost always mechanical parts and the electronic components, such as sensors or motors, get added later on. If some of those components' capabilities existed as part of the 3D-printed parts, designers could reduce costs and part counts. That's the idea behind MIT's new MetaSense concept, which integrates sensing capabilities into mechanical 3D-printed parts.
To understand how this technique works, imagine a typical example of an analog joystick. There are the mechanical parts, including the plastic stick itself, the housing, a joint, and springs. Then there are the electronic potentiometers that exhibit a measurable difference in resistance as the joystick pushes them — each in a single axis. A microcontroller monitors the potentiometers and calculates a vector representative of the two axes. The MetaSense joystick prototype is a single 3D-printed part that replaces all of the components listed above, with the exception of the microcontroller.
Designers can achieve these results using the MetaSense technique with any dual-extruder 3D printer. One extruder pushes out conductive filament while the other extruder pushes out non-conductive flexible filament, such as TPU. The technique relies on capacitive sensing and part geometry. A simple sensor for detecting compression, for example, would contain two conductive portions, the electrodes, connected by flexible spring-like segments. The electrodes connect to a microcontroller through standard wires. When a user pushes down on the sensor, the two electrodes get closer together and produce a detectable difference in capacitance.
Put four of those sensors together, arrayed in the cardinal directions around a central stick, and you have a joystick. Because these are capacitive sensors, they produce analog signals with strengths relative to the proximity of the two electrodes. That is in contrast to switches that have a binary on/off state. Many other devices, including an accelerometer, are also possible. Designers only need to determine where the 3D-printed part can flex and where to position the conductive portions.