On-chip mixing of several biochemical fluids with a specified ratio of concentration factors is a challenging problem in automating biochemical laboratory protocols on a digital microfluidic biochip. The performance of a mixing algorithm depends on resource allocation, e.g., the placement of mixer modules, storage units, boundary reservoirs or dispensers on the chip floor. With a limited number of resources, mixing of a large number of fluids may be slowed down because of the stalls arising out of fluidic constraints during droplet transportation. In this paper, we propose a routing-aware resource allocation technique which can be adopted with two basic mixing algorithms. Simulation results show that on an average, the proposed scheme can reduce the number of droplet crossing paths by 75.4% or by 89.7%, depending on the underlying basic algorithm used for mixture preparation.