MIT Creates New Way to Incorporate Sensors Into 3D-printed Designs

3D printing has become one of the most important tools for engineers when it comes to rapidly prototyping ideas. While the concept has existed for almost half a century, it was only in the past decade that additive manufacturing has gained popularity thanks to widely accessible electronic components and dedicated online communities.

This article focuses on a more advanced implementation of 3D printing: a team of MIT engineers has developed a rotational mechanism with integrated sensing capabilities that can be printed from start to finish without intervention and within the same printable device.

 

In an experimental setup, one of the researchers places their hand at different heights on top of the rotating gear apparatus. Image used courtesy of MIT

 

Advanced 3D Printing

A traditional 3D printing setup typically uses a thermoplastic filament extruded into millimeter-scale layers on top of each other. Some more advanced implementations, however, use multiple extruders at the same time, allowing different types of materials to be used within the same print.

While this can mean filaments with different colors, it can also mean filaments with different properties. For example, water-soluble filaments allow for more complex interconnected moving parts to be printed as one unit because the support material can be rinsed off later on. Additionally, the combination of a conductive filament with a nonconductive filament can drastically impact a design, opening up the possibility of easily embedding circuits and components by printing them as a singular object.

These methods turn the tedious task of manually integrating different components together, especially rotating parts and supporting electronics, into a much simpler procedure. The result is a more stable final product with even more features, such as increased motion and a compact footprint.

 

Integrating Sensors Into a Rotational 3D-printed Mechanism

Recently, a team of MIT researchers led by mechanical engineering graduate student Marwa AlAlawi, published a paper detailing a novel type of rotational mechanism that incorporates sensors into gear systems.

Called a MechSense sensor, this device includes a 3D-printed gear with a portion of its interior built with a conductive material spun around a 3D-printed stationary component. This stationary component features three conductive patches that have the same area as the gear’s conductive segment, separated only by a couple of millimeters of non-conductive material. 

This system is based on capacitive sensing where the embedded conductive interior of the gear acts as one plate of a “capacitor.” Meanwhile, the three patches of the stationary component act as the capacitor plate of three different “capacitors.” The shell of the gear acts as the insulator in between the plates. 

 

Sensor layout of the MechSense sensor. Image used courtesy of MIT

 

As the gear rotates, the conductive patches on the stationary component gradually go from completely covered to completely uncovered by the gear’s conductive plate. This results in a change in the capacitance of all three “capacitors,” which can, of course, be detected through software. This software estimates the gear’s angular position, direction of rotation, and rotational speed.

The team built a system with a full 360 degrees of movement with no need for wires to obstruct its functionality. The entire system was encased in a single 3D-printable object that can be connected to additional control electronics.

 

Using MechSense

To streamline the process of building mechanisms with their system, the MIT engineers developed a software add-on for the computer-aided design application SolidWorks.

Using this software, a designer can specify their desired number of rotating and stationary components, and the software will automatically incorporate sensor patches into their model. The model can then be immediately 3D printed as a functional MechSense sensor-enabled prototype.

 

This distance-measuring wheel includes integrated sensing that measures irregular geometries and open spaces. Image used courtesy of MIT

 

According to the MIT team, this can be used to rapidly prototype devices such as turbines or motors as well as tangible rotating sensors for augmented and virtual reality interfaces. As a proof of concept, the researchers have already created a couple of devices using MechSense, such as a smart desk lamp and a planetary gearbox.

In the future, the team plans to test different materials to increase the stability of their system, make their sensors more resistant to external noise, and enable their system to be used with other types of moving mechanisms.

 

The Future of 3D Printing

3D printing opens new possibilities in both the prototyping and product manufacturing process. MIT's novel approach with its 3D-printed embedded electronics rotational systems gives both electrical and mechanical engineers the opportunity to create unique systems far quicker and with more functionalities and use cases than before.