Piezoelectric rotational mixer based on a first bending vibration mode

Area of Science:

• Microfluidics and MEMS (Micro-Electro-Mechanical Systems)
• Acoustic Engineering
• Biomedical Device Technology

Background:

• Manual mixing of small liquid volumes, such as blood samples, is common in medical testing but can be labor-intensive and prone to error.
• Existing automated mixing solutions may be too large or complex for certain point-of-care or microfluidic applications.
• Acoustic streaming, the fluid flow induced by acoustic waves, offers a non-contact method for fluid manipulation.

Purpose of the Study:

• To propose and experimentally validate a novel miniature piezoelectric mixer for generating rotational liquid flow.
• To investigate the feasibility of using acoustic streaming for automated mixing in millimeter-scale channels.
• To characterize the performance of the piezoelectric mixer by analyzing flow velocity under varying electrical parameters.

Main Methods:

• A miniature piezoelectric mixer (14 × 14 × 10 mm) with a 7 mm through-hole was designed and fabricated.
• Piezoelectric elements were bonded to the mixer's sides and excited with AC voltages to induce the first bending vibration mode.
• Experimental measurements were conducted to observe and quantify the induced rotational flow (acoustic streaming) within the through-hole, with a plastic test tube inserted to prevent contamination.

Main Results:

• The piezoelectric mixer successfully generated rotational liquid flow within the through-hole via acoustic streaming.
• The induced flow velocity was found to be dependent on the amplitude and frequency of the applied AC voltages.
• The prototype demonstrated effective mixing of liquid within an inserted test tube.

Conclusions:

• The miniature piezoelectric mixer effectively utilizes acoustic streaming for non-contact, rotational liquid mixing in millimeter-scale devices.
• This technology presents a viable solution for automating micro-volume liquid handling in applications such as medical diagnostics.
• Further optimization of voltage parameters can precisely control mixing efficiency.