Acoustic levitation forces can be used to manipulate small objects and liquid without mechanical contact or contamination. To use acoustic levitation for contactless robotic grippers, automated insertion of objects into the acoustic pressure field is necessary. This work presents analytical models based on which concepts for the controlled insertion of objects are developed. Two prototypes of acoustic grippers are implemented and used to verify the lifting of objects into the acoustic field experimentally. Using standing acoustic waves and dynamically adjusting the acoustic power, the lifting of high density objects (≥ 7 g/cm³) from acoustically transparent surfaces is demonstrated. Moreover, a combination of different acoustic traps is used to lift lower density objects from acoustically reflective surfaces. The provided results open up new possibilities for the use of acoustic levitation in robotic grippers, which have the potential to be applied in a variety of industrial applications.