This is a laboratory activity where the students make their own printed sensors and perform a calibration curve so they can be used in a real context. It will give an idea of how sensors can be made and how generally a physical variation of temperature, relative humidity or UV can be indirectly determined by measuring the electrical resistance or current variation. Depending on the number of students, the “class” can be divided in several groups of three students or it can be performed in small groups of two-to-five so everyone can be able to print at least one of the layers required in this activity.