I won’t go into too much detail because the instrument I am currently developing is patent-protected. Although I am not the patent holder, I signed a confidentiality agreement when I joined the company, so I cannot disclose the key technologies. However, I can give a brief overview since the underlying principles have already been published. I am not the first postdoc responsible for this project; before me, a PhD graduate also worked on developing this instrument.

First, there is a microfluidic channel—or in our case, we use a capillary. This microfluidic channel or capillary is attached to a piezoceramic device (piezo), which converts electrical signals into sound waves. The input electrical signal is generally a sinusoidal wave.

We introduce particles into the microfluidic channel, using either a pressure pump or a syringe pump (personally, I prefer the pressure pump because it provides higher precision). Normally, under the flow of the fluid, particles are somewhat focused toward the center of the channel; this is called hydrodynamic focusing, though the focusing effect is not always optimal.

If we turn on the piezo at this point, the sound waves interact with the particles and fluid, causing the particles to focus more precisely at the center of the channel. This is known as acoustic focusing.

Acoustic focusing not only keeps particles flowing along the center of the channel but also stretches them. Once particles are stretched, they produce interference under a laser, forming fringes. By analyzing the characteristics of these fringes, such as the number of fringe rings, we can determine the mechanical properties of the particles.

Of course, this project is currently at the development stage. Even at my current stage, I can only acquire partial data, so I have not yet been able to analyze it.