A LoC (Lab on a Chip) is described to analyze surface properties of fluid drops. Substrates with cavities near the edge are filled with fluids that have a contact angle greater than 90.degree.. The surfaces of two different drops can be brought in contact with one another by using Coulomb forces. Several experiments can be carried out while the drops are in contact: the concentration of the fluid in each drop can be altered, tangential and normal forces can be applied to the contact surface, voltage differences across and current flow through the contact surface can be monitored. MEMS pumps can be used to mix reagents or buffers with the fluid to determine the protein concentration or to extract DNA from whole cells, respectively. Substrates holding optical components can be used to align fibers with either lasers or receivers. The alignment is automatic and controlled by a control unit.