The prototype uses a TTP223 capacitive touch sensor as input, an Arduino UNO as the controller, and an MG90S servo as the actuator. The servo drives the rack-and-pinion mechanism, which transfers rotational motion into vertical rack movement. This movement then pushes and pulls the folded paper structure to create contraction and expansion.
A separate 5V battery pack powers the servo for more stable motor operation, while Arduino handles touch detection, timing control, and the transition between idle and active breathing rhythms.
The interaction is designed as a speed change, not a change in movement range: the servo keeps the same sweep range, while the cycle shifts from a slow idle rhythm to a clearer active rhythm.
The prototype brings together a folded paper ball, a rack-and-pinion movement, a capacitive touch pad, and a wooden base. The paper structure is anchored at the bottom and driven from the top, allowing it to shift between contraction and expansion. This physical movement turns the folded form into a visible breathing rhythm that users can follow through touch.
This project revealed the difficulty of turning a folded paper structure into a controlled breathing interface. The paper ball could express contraction and expansion visually, but its movement depended heavily on precise alignment between the fixed base, the vertical rack, and the upper contact point. The idle and active states also required careful pacing: the motion had to be visible enough to guide breathing, while remaining subtle enough to feel calm. Future iterations could focus on improving the rack stability, refining the device finish, hiding technical components more cleanly, and testing whether users can intuitively follow the paper rhythm in waiting scenarios.