Idea

SensorSnaps are low-power wireless sensor nodes that seamlessly integrate into caps of fabric snap fasteners. SensorSnaps provide a new technique to quickly and intuitively augment any location on the clothing with sensing capabilities. SensorSnaps securely attach and detach from ubiquitous commercial snap fasteners. Using inertial measurement units, the SensorSnaps detect tap and rotation gestures, as well as track body motion.

Details in UIST paper below

SensorSnaps: Integrating Wireless Sensor Nodes into Fabric Snap Fasteners for Textile Interfaces. Proc of UIST'19

See the video here:

Bluetooth sensor nodes

We designed a custom 4-layer PCB to minituarize the design. We use a powerful nRF52832 chip as the microcontroller and Bluetooth tranceiver. To improve the power consumption and data rate, we use the uVision IDE from ARM. Alterntively, Arduino could be used on the microcontroller.

Mechanical enclosure

The enclosure was printed using Form 2 SLA printer. We used SLA, as the feature size were too small for an FDM printer.

Attachment to fabric

SensorSnaps are attached to the off-the-shelf snaps with a screw. This allows for a quick and removable connection. We tested with the innexpensive plastic snaps kit, found on Amazon, such as this one.

Applications

We present applications in which the SensorSnaps are used as gestural interfaces for a music player controller, cursor control, and motion tracking suit.

Music player

As a basic functionality, SensorSnaps can replace snap fastener caps on off-the-shelf clothing. We replaced cufflinks on a dress shirt with SensorSnaps. The SensorSnap was connected to a music controller Android app running on a mobile phone (Google Pixel 2) through Bluetooth. The app permitted choosing an audio file (i.e., song, podcast, audiobook), and using the tap gesture to either play or pause the audio file. The rotation gesture allowed to change the volume of the audio being played. Direction of rotation increased or decreased the volume level. The angle controlled the magnitude of the volume change. Double-tapping allowed to change between volume and time modes. In the time mode, the rotation gesture is reused for either fast-forwarding or rewinding of the audio. Direction of rotation triggers fastforward or rewind. The angle of the rotation controlled the speed of the fast-forwarding or rewinding.

Motion tracking

Motion tracking can provide useful information for sports, medicine and gesture-controlled devices. Traditionally, optical motion tracking is done by tracking reflective markers with multiple cameras. Using 9-axis IMUs attached to different body parts, motion tracking can be done without external cameras. Currently, the IMU approach is still cumbersome and requires a special suit equipped with IMUs. The SensorSnaps could be added to off-the-shelf clothing to enable motion tracking on demand. We attached SensorSnaps to the arm, forearm and torso and quaternion orientation data is continuously sent to the computer

Assistive Device

The SensorSnaps could be potentially useful as interfaces for Augmentative and Alternative Communication. Users with motor impairment might have different capabilities from what standard interfaces allow. The SensorSnaps could be placed anywhere on the clothing. The number and the location of the SensorSnaps could be tailored to individuals’ needs. In this application we imagine an individual with limited or no finger control, making it hard to use standard hand-controlled input interfaces. We added a SensorSnap to the shirt’s cuff. By supination and pronation of the forearm, and movement, flexion, and extension of the arm, the SensorSnap was used as a pointing device for a computer screen (Figure 13). The x-coordinate would move proportional to changes in the x- axis, while the y-coordinate to changes in the y-axis of the gyroscope.