Programming layer-by-layer liquid phase epitaxy in microfluidics for realizing two-dimensional metal-organic framework sensor arrays

Detection of small molecules such as phthalates is a persistent challenge in current point-of-care sensors technology for environmental applications. Here, owing to their porous crystalline lattice and tuneable molecular specificity, two-dimensional metal-organic frameworks (2D MOFs) present unique opportunities as an emerging class of transducers. Addressing the challenges of efficient nanomaterial design and device prototyping based on MOFs, this work demonstrates programmable liquid-phase epitaxy (LPE) growth of a Nickel(II) and 2-aminoterephthalic acid (BDC-NH2) based 2D MOF in modular microfluidic circuits on chip. Fully automated layer-by-layer (LbL) LPE yields homogeneous growth of crystalline 2D Ni-BDC-NH2 or Ni-MOF of thicknesses ranging from 2 to 25 nm on Si/SiO₂ substrate. Employing specially designed chips with metal microelectrode arrays (MEAs) as substrates, LbL-LPE approach is successfully used to carry out scalable integration of 2D Ni-MOF sensor arrays with high reproducibility. Using electrochemical impedance spectroscopy (EIS), the sensor chips are deployed for detection of diisobutyl phthalate (DiBP), one of the plasticizers linked to serious illnesses of the endocrine system, in concentration range from 1 to 20 µg/mL.