The absence of physical interfaces creates challenges when interacting with touchscreen technology. This study aims to investigate an innovative haptic solution for interacting with graphical user interfaces. A motorized shape-changing rotary knob interface, HapKnob, has been developed, achieving seven distinctive shape configurations and various force feedback renderings. HapKnob presents a compact design and can provide additional configurations and combinations based on user needs. The anticipated results hold the potential to advance the development of future user interfaces, especially in situations where visual interaction is unavailable.