# A Slanted-Finger Interdigitated Transducer Microfluidic Device for Particles Sorting

## TL;DR

This paper introduces a new microfluidic device that uses slanted-finger transducers to sort particles of different sizes with high efficiency and purity.

## Contribution

The novel slanted-finger interdigitated transducer design enables a wider frequency range and adjustable operating frequencies for particle sorting.

## Key findings

- The device achieves sorting efficiency and purity exceeding 96% for mixed polystyrene microspheres.
- The operating frequencies generate a standing wave acoustic path of approximately 200 μm.
- The device can sort microspheres of various sizes in a label-free and high-purity manner.

## Abstract

Sorting particles or cells of specific sizes in complex systems has long been a focus of many researchers. Acoustic surface waves, which generate acoustic radiation forces on particles or cells and, thus, influence their motion, are commonly used for the non-destructive separation of particles or cells of specific sizes. In previous studies, the frequency of acoustic surface wave generation has been limited by the interdigitated transducer (IDT). To extend the effective operating frequency range of the IDT, a slanted-finger interdigitated transducer (SFIT) with a wide acoustic path and multiple operating frequencies was designed. Compared with traditional acoustic sorting devices, which suffer from a limited frequency range and narrow acoustic paths, this new design greatly expands both the operating frequency range and acoustic path width, and enables adjustable operating frequencies, providing a solution for sorting particles or cells with uneven sizes in complex environments. The optimal resonance frequency is distributed within the 32–42 MHz range, and the operating frequencies within this range can generate a standing wave acoustic path of approximately 200 μm, thus enhancing the effectiveness of the operating frequencies. The microfluidic sorting device based on SFIT can efficiently and accurately sort polystyrene (PS) with particle sizes of 20 μm, 30 μm, and 50 μm from mixed PS microspheres (5, 10, 20 μm), (5, 10, 30 μm), and (5, 10, 50 μm), with a sorting efficiency and purity exceeding 96%. Additionally, the device is capable of sorting other types of mixed microspheres (5, 10, 20, 30, 50 μm). This new wide-acoustic-path, multi-frequency sorting device demonstrates the ability to sort particlesin a high-purity, label-free manner, offering a more alternative to traditional sorting methods.