Coffee Ring-Inspired Approach toward Oriented Self-Assembly of Biomimetic Murray MOFs as Sweat Biosensor

The emergence of metal-organic frameworks (MOFs) has sparked intensive attention and opened up the possibility of "crystal engineering." However, low conductivity, slow diffusion of guest molecules, as well as powder forms always hinder the development of MOF application, especially for biosensors and bioelectronics. Herein, a coffee ring-inspired strategy toward oriented self-assembly of a biomimetic MOF film following Murray's law is proposed, which can effectively reduce the transfer resistance. The approach includes two types of self-assembly, evaporation-driven and heteroepitaxy self-assembly, and endows the centimeter-expanded MOF film with oriented macropores, mesopores, and micropores. The Murray MOF network enables greatly enhanced electrons and mass transfer efficiency for electrochemical sensing. Also, the newly discovered lactate and glucose sensing abilities in a wide pH hold striking potential in new generation of wearable sweat biosensors, miniature bioelectronics, and lab-on-a-chip devices.