This work showed that respec�ve rates in compe�ng ac�va�on processes can be tuned using the poly-L-lysine immobilized on the surface of a microfluidic channel. Challenges encountered in the experimental realiza�on of robust steady-state output in CRNs o�en relates to finding the balance between the reac�on rates of various feedback loops in the network. We explored the poten�al of using a surface-coupled reac�on to create compe�ng ac�va�on processes around a very simple acid-base equilibrium. We demonstrated that the obtained output signals are not only tunable and robust, but also applicable for informa�on processing purposes. The incorpora�on of other func�onal groups in the reac�ve layer, or the fabrica�on of devices with a greater control over the surface-to-volume ra�o, could maximize the poten�al of PLL-coated surfaces in the design of chemical feedback systems.to extend this approach to many other chemical reac�ons. We envision that the applica�on of reac�ve surfaces in microfluidic devices as demonstrated here will enable the design of novel CRNs with feedback loops capable of local regula�ons of biochemical reac�ons.