An ultrasound transducer unit (12), e.g. probe, is configured with a friction guiding function. The transducer unit comprises a vibration generating means at a tissue contact area, and has means for sensing a sliding direction of the transducer unit across a tissue surface (42) at which the contact area is incident. The tissue surface may be an external skin surface or an internal tissue surface, e.g. in case of a catheter. A control means is operable to control the vibration of the vibration generator to adjust a level of friction at the tissue contact area. This is used by the control means to implement a friction guiding function for guiding a user in sliding the unit across the incident surface, e.g. toward a target location (44), based on controlling the friction level responsive to the sensed sliding direction, for instance providing lower friction when sliding is in a target direction, while leaving other directions with relative higher frictional resistance.
