A portable hemodialysis system is provided including a disposable cartridge and a reused dialysis machine. The first and second bilayers are joined together along perimeters of the first and second bilayer outer layers and first and second bilayer inner layers, respectively. The method disclosed for characterizing the sputter target material employs the phase change and amplitude magnitude data for calculating cleanliness factors and generating pareto histograms. The sensor senses a reflected light beam caused by movement of a user’s digit movement on the light pervious area at a velocity which can be sensed by the sensor.