# Integrated Hybrid Tweezer for Particle Trapping with Combined Optical and Acoustic Forces
## 1 Introduction
designed acoustic tweezers based on flat holographic transducers to selectively trap and move one particle independently [23]. In 2020, [PERSON] et al. designed acoustic tweezers based on circular, slanted-finger piezoelectric interdigital transducers to enable the dynamic and reconfigurable manipulation of micro-objects using multi-tone excitation signals [24]. Due to the high accuracy and selectivity of optical tweezers and the large-scale trapping ability of acoustic tweezers, it is meaningful to combine them to meet the requirement of accuracy and efficiency in the field of cell capture for biomedicine. Recently, some studies have tried to combine optical and acoustic tweezers for particle sorting [32] and trapping [33; 34; 35]. However, integrating both optical and acoustic tweezers on a chip remains unexplored. The state of the art of optical and acoustic tweezers are listed in Table 1. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Type of Tweezer** & **Tweezer Composition** & **Captured Particle** & **Type of Force** & **Feature** & **Reference** \\ \hline \multirow{4}{*}{Free-space optical tweezer} & The optical fiber & Yeast cells & Optical force & Multiple yeast cells 3D stable trapping & [6] \\  & The holographic lens group & 2 \(\upmu\)m diameter silica beads & Optical force & The 3D shape control of the optical forces & [9] \\  & The metasurface & Polystyrene particles with a diameter of 4.5 \(\upmu\)m & Optical force & Polarization-sensitive 2D manipulation & [10] \\ \hline \multirow{4}{*}{Near-field optical tweezer} & The strip and rib & \multirow{2}{*}{Red blood cells} & \multirow{2}{*}{Optical force} & Developing a methodology for quantitatively studying red blood cells & [11] \\  & waveguides & & & & \\ \cline{1-1}  & The V-groove waveguide & Polystyrene nanoparticles & Optical force & The much higher capability to trap nanoparticles & [12] \\ \cline{1-1}  & The one-dimensional (1D) & The polystyrene particle with a refractive index of 1.56 and a & Optical force & Efficient optical trapping and transportation in a peristaltic way & [13] \\ \cline{1-1}  & photonic crystal waveguide & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \cline{1-1}  & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The state of the art of optical and acoustic tweezers and the proposed tweezer. In this work, we propose an integrated hybrid tweezer that is capable of particle capturing, controlled reorientation, the separation of particles with significantly different refractive indices, and reducing the volume and cost to a certain extent. This integrated hybrid tweezer is capable of trapping particles of 5 \(\upmu\)m in diameter. The acoustic and optical forces generated by an interdigital transducer (IDT) and the evanescent optical field can be balanced to trap the particle. Trapping the particles with different refractive indices (\(n\) = 1.4, 1.5, and 1.6) and controlling their positions can be achieved by adjusting the optical power in the waveguide or the voltage applied to the IDT.