This paper reports on a compact new cross-flow 3D mixer that is integrated with a gradient generator into one device for toxicology applications. The device has two parts: the first mixes two solvents while the second generates gradients of the obtained solutions. The outlet of the 3D cross-flow mixer is integrated with a linear channel that aids in achieving this gradient by changing flow rates. The dye-visualization test confirm the functionality of mixer and gradient. The mesh structure of the mixer provided excellent mixing regime and is confirmed by experimental and simulation results. The compact size (25 × 25 × 3 mm) and the reduced cost ($1.5) of the device enable the device to be disposable. We aim to study doxorubicin drug at different concentration generated by the device to culture human embryonic kidney (HEK) from the 293-cell line enabling the devices to be used for cellular studies. The carefully designed geometry of the device finds applications in drug toxicology testing devices, micro-total analysis systems (μ- TAs),and other lab-on-chip devices.