BAW-based Acoustic Tweezers For Patterning And Encapsulation Of Micro-nano Particles

The research and application of micro-nano manipulation technology have become essential disciplines of science and technology today.They have led to significant progress and even revolutionary breakthroughs in other fields of science and technology.At present,micro-nano manipulation technologies are mainly divided into contact and non-contact.Acoustic tweezers,a representative manipulation technique in the non-contact category,have proven to be an essential tool for micro-nano particle assembly due to their versatility,non-invasiveness,and biocompatibility.Acoustic tweezers utilize two physical effects of ultrasound fields:acoustic radiation force and acoustic streaming to achieve aggregation,separation,alignment,and patterning of micro and nanoparticles.There are two types of standing wave acoustic tweezers,standing surface acoustic wave(SSAW)and bulk acoustic wave(BAW)based standing wave acoustic tweezers.Compared with SSAW acoustic tweezers,BAW acoustic tweezers can handle high throughput liquids and are more suitable for preparing composite materials and assembling microstructures.Therefore,aspects of BAW acoustic tweezer micro-nano-particle patterning manipulation and encapsulation are investigated.In this paper,we address the process of assembling patterned micro and nanostructures by standing wave acoustic tweezers,build a bulk acoustic wave standing wave acoustic tweezer manipulation platform,and observe and analyze the particle assembly process by a high-speed camera.By adjusting the acoustic field parameters such as phase difference,acoustic intensity,frequency,and radiation time,the effects of acoustic radiation force on the assembly process of patterned micro-nano structures and the patterned size shape and ordered structure are investigated.The dynamic information and laws of the assembly characteristics of patterned arrays with the change of external field are found..The transient evolution of patterned micro-nano-structures assembled by standing wave acoustic tweezers was clarified.The principle of standing wave acoustic tweezers manipulation for assembling patterned micro-nano-structures was obtained.The liquid metal Ga,with excellent mobility and high electrical conductivity,is selected as the target patterned particles.The arrangement behavior of liquid metal Ga particles under different acoustic field parameters is investigated using a visualized BAW acoustic tweezer manipulation platform build independently.Piezoelectric excitation achieves deformable dynamic patterning manipulation of particles with different orientations to form one-dimensional and two-dimensional standing wave fields,thus arranging liquid metal Ga particles into nodal line and dot matrix patterns.In the past decade,gallium-based liquid metals and their alloys have been used in flexible wearable devices due to their high electrical conductivity and infinite deformation that can meet the needs of soft electronic applications.Building electronic devices requires the ability to pattern materials into individual electronic components,i.e.liquid metals need to be patterned for use in stretchable and soft electronic devices,hence the growing emphasis on patterning techniques for particles.In order to pattern the particles more efficiently and encapsulate the patterns in an elastic matrix to fabricate more economical,flexible devices.This paper proposes a new particle patterning and encapsulation method by combining the current liquid metal encapsulation technology and theoretical methods of particle manipulation by BAW acoustic tweezers.The magnetic liquid metal in the PDMS precursor medium is patterned and encapsulated using a one-dimensional BAW and magnetic field coupling by improving the manipulation platform of standing-wave acoustic tweezers.The feasibility of the method is experimentally demonstrated.