As the DiaCHIP relies on antibody-antigen interactions, the antigens first have to be synthesized and immobilized inside the device. Given that the whole device is a microfluidic system, it was most convenient to do this directly in the flow-chamber, where detection will finally take place. The flow-chamber consists of two surfaces separated by a gap that can be flushed with liquids. On the one surface DNA molecules providing the information for the antigens are attached and can be transcribed and translated into protein when a cell-free expression mix is flushed through the chamber. Proteins then diffuse until reaching the second surface that specifically captures the proteins encoded by the immobilized DNA. After several washing steps to remove remaining expression-mix the flow-chamber is coated with antigens and ready for detection.