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-mu m-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 degrees C to trap the 40-mu m-diameter copper wires with a length of 1-14 mm.