Gallium nitride (GaN) is a compound semiconductor which has advantages to generate new functionalities and applications due to its piezoelectric, pyroelectric, and piezo-resistive properties. Recently, surface acoustic wave (SAW) based acoustic tweezers were developed as an efficient and versatile tool to manipulate nano- and micro-particles aiming for patterning, separating and mixing biological and chemical components. Conventional piezoelectric materials to fabricate SAW devices such as lithium niobate suffers from its low thermal conductivity and incapability of fabricating multiphysical and integrated devices. This work piloted the development of a GaN-based Acoustic Tweezer (GaNAT) and its application in manipulating micro-particles and biological cells. For the first time, the GaN SAW device was integrated with a microfluidic channel to form an acoustofluidic chip for biological applications. The GaNAT demonstrated its ability to work on high power (up to 10W) with minimal cooling requirement while maintaining the device temperature below 32C. Acoustofluidic modelling was successfully applied to numerically study and predict acoustic pressure field and particle trajectories within the GaNAT, which agree well with the experimental results on patterning polystyrene microspheres and two types of biological cells including fibroblast and renal tumour cells. The GaNAT allowed both cell types to maintain high viabilities of 84.5% and 92.1%, respectively.