Capture of Individual Micrometal Wires in Air by Ultrasonic Tweezers

In this paper, a strategy to capture individual micrometal wires in air by ultrasound is demonstrated. Curved and flattened tip of a vibrating needle excited by a sandwich-type transducer, operating at about 45.8 kHz, is employed to capture micrometal wires in air. A 40-μm-diameter copper wire with a length of 1-14 mm can be trapped stably by ultrasound and transferred through any 3-D path in air by moving the transducer. The trapping is caused by the acoustic radiation force. The trapping capability, which is defined by the maximum length of a trapped micrometal wire, increases with the increase of the needle vibration, and decreases when the needle vibration is too large. Decreasing the manipulating edge´s thickness of the needle´s tip and selecting proper material for the needle can enhance the trapping capacity. The shape of the needle´s tip also influences the trapping capacity. The manipulating tip has a temperature rise up to 38.5°C to trap the 40-μm-diameter copper wires with a length of 1-14 mm.