Micro-feeding of nanoparticles under ultrasonic vibration

Understanding the collective flow of nanoparticles is important for handling the storing, dosing, and conveying of nanoparticles. We experimentally studied the discharge characteristics of nanoparticles from the hopper through a microchannel under ultrasonic vibration. Results show that ultrasonic vibration can effectively trigger the flow of jammed nanoparticles, which flows in the form of aggregates at a controllable discharge rate as low as 0.1 mg/s. The aggregate properties were obtained from high-speed image processing technology. The multi-stage flow mechanism was revealed: particle re-arrangement at low amplitude and wall slip at high amplitude. Given this, the discharge rate model was developed by introducing an exponential function G(Fr) into the traditional Beverloo equation. The modified model describes both the self-organized behavior at low amplitudes and velocity scaling caused by acceleration at high amplitudes, successfully predicting the discharge rate within +/- 10% errors.