# Integrated Hybrid Tweezer for Particle Trapping with Combined Optical and Acoustic Forces
## 1 Introduction  
Tweezers are tools that manipulate the positions and movements of very small objects. For particles with sizes in the micrometers and nanometers, there are many types of tweezers, such as optical tweezers (can be used in molecular sensing, precision molecular manipulation, and cell assembly [1; 2]), acoustic tweezers (can be used in particle separation, material manufacture, cell transportation, sorting, and enrichment [3]), magnetic tweezers (can be used in parallel single-molecule fluorescence detection measurements and cell transport [4; 5]), dielectrophoretic tweezers (can be used in medical diagnostics, material characterization, drug discovery, cell therapeutics, and particle filtration [6]), and plasmonic tweezers (can be used in biomanipulation, spectrographic sensing and imaging, and particle transport and sorting [7]), etc. Various methods based on optics [8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19], acoustics [20; 21; 22; 23; 24], magnetism [4; 5; 25], dielectrophoresis [6], and plasma [7; 26] for the remote driving of particles, have been developed. In 1986, [PERSON] proved that particles could be trapped by the gradient force generated by a light beam [27]. Optical tweezers are mainly divided into two categories, namely free-space optical tweezers [8; 9; 10] and near-field optical tweezers [11; 12; 13; 14; 15; 16; 17; 18; 19]. Free-space optical tweezers mainly include tweezers based on lens group [9], optical fiber tweezers [8], and optical tweezers based on metasurfaces [10]. In order to achieve complex optical manipulation, in 2017, [PERSON] et al. proposed optical fiber tweezers that can trap multiple particles [8]. In 2018, [PERSON] et al. implemented a vector beam holographic optical trap array based on holographic optical trap technology [9]. Due to the limited beam control ability of optical fibers, optical tweezers based on metasurfaces were proposed, and in 2020, [PERSON] et al. achieved polarization-sensitive particle manipulation using metasurfaces [10]. [PERSON] and [PERSON] were the first to realize the manipulation of polystyrene microspheres on optical waveguides [28]. Thereafter, manynear-field optical tweezers have been reported [11; 12; 13; 14; 15; 16; 17; 18; 19]. Near-field optical tweezers mainly include optical tweezers based on waveguides and optical tweezers based on resonant cavities. In 2018, [PERSON] et al. manipulated biological cells using optical waveguides [11], and [PERSON] et al. proposed a V-groove waveguide as an appropriate platform for nanoparticle trapping and transporting [12]. In these works, particles are pushed by optical scattering forces and moved forward with traveling optical waves along waveguides. In some other cases [29; 13], the positions of traps can also be effectively controlled by changing the wavelength or forming standing waves in waveguides. Resonant cavities can enhance optical fields. In 2020, [PERSON] et al. achieved the stability enhancement of resonance for particle capture based on a self-locked scheme [14]. In 2022, [PERSON] et al. achieved sufficient optical force for base-pair resolution measurements of multiple molecules by forming standing waves in microrings [15]. In 2022, [PERSON] et al. utilized photonic crystal cavities to manipulate viruses with large trapping areas [16]. To ease the observation of particles in some studies, photonic crystal cavities [30; 31] were used to establish a strong local light field to trap the particles at fixed positions. The use of acoustic methods to capture particles has been extensively studied as well. Since [PERSON] analyzed the acoustic force, controlling particle movement with an acoustic wave has been widely studied for objects with sizes ranging from nanometers to millimeters [3]. For acoustic tweezers, some studies on integrated acoustic tweezers used the acoustic radiation force [21] and streaming-induced drag force [22] to manipulate particles based on conventional interdigital transducers. Meanwhile, in 2019, [PERSON] et al.