title: Numerical study of acoustophoretic motion of particles in a PDMS microchannel driven by surface acoustic waves.
abstract: We present a numerical study of the acoustophoretic motion of particles suspended in a liquid-filled PDMS microchannel on a lithium niobate substrate acoustically driven by surface acoustic waves. We employ a perturbation approach where the flow variables are divided into first- and second-order fields. We use impedance boundary conditions to model the PDMS microchannel walls and we model the acoustic actuation by a displacement function from the literature based on a numerical study of piezoelectric actuation. Consistent with the type of actuation, the obtained first-order field is a horizontal standing wave that travels vertically from the actuated wall towards the upper PDMS wall. This is in contrast to what is observed in bulk acoustic wave devices. The first-order fields drive the acoustic streaming, as well as the time-averaged acoustic radiation force acting on suspended particles. We analyze the motion of suspended particles driven by the acoustic streaming drag and the radiation force. We examine a range of particle diameters to demonstrate the transition from streaming-drag-dominated acoustophoresis to radiation-force-dominated acoustophoresis. Finally, as an application of our numerical model, we demonstrate the capability to tune the position of the vertical pressure node along the channel width by tuning the phase difference between two incoming surface acoustic waves.
authors.affiliation: Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, PA 16802, USA. junhuang@psu.edu.
authors.forename: Nitesh
authors.initials: N
authors.lastname: Nama
authors.forename: Rune
authors.initials: R
authors.lastname: Barnkob
authors.forename: Zhangming
authors.initials: Z
authors.lastname: Mao
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Kähler
authors.forename: Francesco
authors.initials: F
authors.lastname: Costanzo
authors.forename: Tony Jun
authors.initials: TJ
authors.lastname: Huang
mesh_terms: D004129:Dimethylpolysiloxanes; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods*; D008962:Models, Theoretical; D009556:Niobium; D009757:Nylons; D010087:Oxides; D013016:Sound; D013499:Surface Properties
chemical_list: D004129:Dimethylpolysiloxanes; D009757:Nylons; D010087:Oxides; C085707:poly(dimethylsiloxane)-polyamide copolymer; D009556:Niobium; C091692:lithium niobate