In this article, we demonstrate a manufacture of the lab-on-paper device. The paper presents a technology of laser thermal transfer of stearine, into a porous paper often used in chemistry. Such a rapid, one-step technology was developed to obtain a paper-based analytical device with using only paper, stearine disc and CO2 laser plotter. Melted in stearine makes hydrophobic surface which is microfluidic wall for analyzed fluids. The results show that paper-based analytical device is a cheap pH tester for a one-time use. Moreover, the whole device can be integrated with much more advanced chemicals or simple electronic for image analysis.