University of Washington researchers 3D printed mechanical sensors and switches from standard plastic filament that can send data to Wi-Fi devices without using any electronics. As the engineers explain in this video, the plastic devices either reflect or absorb the ambient Wi-Fi signals and that effect is translated into a signal of zero or one. From the Printed Wi-Fi research page:
Specifically, we introduce the first computational designs that 1) send data to commercial RF receivers including Wi-Fi, enabling 3D printed wireless sensors and input widgets, and 2) embed data within objects using magnetic fields and decode the data using magnetometers on commodity smartphones. To demonstrate the potential of our techniques, we design the first fully 3D printed wireless sensors including a weight scale, flow sensor and anemometer that can transmit sensor data. Furthermore, we 3D print eyeglass frames, armbands as well as artistic models with embedded magnetic data. Finally, we present various 3D printed application prototypes including buttons, smart sliders and physical knobs that wirelessly control music volume and lights as well as smart bottles that can sense liquid flow and send data to nearby RF devices, without batteries or electronics.