Liquid detection sensors are attached to both sides of a robotic arm end effector of a semiconductor wafer process system. The sensor mechanism or probe is situated on the front side and backside of the end effector, designed with electrical lines that are traced onto a polyester base material. The electrical lines are positioned in a serpentine formation. The high conductance of the sulfuric acid in the copper sulfate solution acts as the conductor between the traced lines. When the conductive liquid comes in contact with the traced lines, the lines short and the sensor activates or turns on.