where, r1 and r0 are the entrance radius and exit radius of the needle, respectively; P is the pressure exerted and θ is the angle between the needle and the deposition surface. In addition, τy, n, and K are the yield stress, flow index, and viscosity index, respectively. Note that n and K are related to temperature and θ is related to the length of the needle. As previously analysed by extruding-based bioprinting for pressure drop within nozzle diameter Ds and nozzle length L[39], the flow rate can be determined by the following equation: