Quantity   Component name
1 × Curved touch arc (disk segment) 17 mm chord, 4.02 mm tall, mutual-capacitance electrodes on the curved face: 1 TX, 16+ RX, evenly spaced. Core.
1 × Linear resonant actuator (LRA) Smartwatch-class vibration motor, 12 × 5 × 3 mm, bonded to the flat face of the arc. Creates the detent clicks. Core.
1 × TI DRV2605L haptic driver Drives the LRA, with back-EMF sensing and auto-resonance tracking. Core.
1 × Azoteq IQS7211E touch controller Mutual-capacitance controller that reads finger position on the arc. Any equivalent controller works. Core.
1 × Silicone damping isolator 1 mm thick, 50–70 Shore A. Keeps vibration at the fingertip, not the palm rest. Core.
1 × Printed circuit board 0.6–1.6 mm thick. Carries the controller, driver, and optional accelerometer. Core
1 × Raspberry Pi Pico (RP2040) Bench prototype only. Sends scroll reports over USB HID. Not needed in a laptop, which uses its existing controller.
1 × Bosch BMA530 accelerometer Optional, for tilt-to-horizontal-scroll only. Senses board flex, at least 2 mm from the post anchor.
1 × Metal post with silicone sleeve Optional, for tilt-to-horizontal-scroll only. Transfers side pressure from the arc to the PCB.