Trapping of biomolecules using bulk acoustic wave resonators

Abstract

Introduction Developing micro/nano scale devices for biosensing applications have triggered a lot interests in recent years. Miniaturizing the transducer size often increases the limit of detections (LOD) of the biosensor which is largely benefited by its high surface to volume ratio. However, fundamental limitations for further improvement of the LOD of micro/nano scale biosensors are the mass transport and binding affinity limitations. Active methods are required to enhance the transportation rate of the target analytes to the sensor surface. Dielectriphoretices (DEP), optical tweezers (OT) and acoustical tweezers (AT) have been demonstrated to manipulate different types of cells, proteins and DNAs [1-3]. However, these methods either limited to larger bioparticles (AT), charge states of the targets (EDP) or required expensive tools (OT). In this work, we developed a universal method to manipulate biomolecules based on microfabricated Bulk Acoustic Wave Resonators (BAW) which is regardless of the sizes, charges and shapes of the targets. The resonators can trigger microvortices in liquids and further trap biomolecules to the stagnation region of the microvortices, thus, enhancing the transportations of the targets and improves the LOD of the biosensing. To understand the mechanism of the trapping induced by BAW, we calculate the velocity and the force element by finite element modeling simulations. The trapping effects are demonstrated by 5 um polystyrene microspheres and fluorescent labeled human IgGs which are less than 10 nm. It shows that the hydrodynamic force combined with acoustic trapping have great potential to manipulate a wide range of biomolecules and facilitate the biosensings.