Molecularly Imprinted Polymer Sensors

An interdigitated electrode sensor was designed and microfabricated for measuring the 11 changes in the capacitance of three phosphate selective molecularly imprinted polymer (MIP) 12 formulations, in order to provide hydroponics users with a portable nutrient sensing tool. The 13 MIPs investigated were synthesised using different combinations of the functional monomers 14 methacrylic acid (MAA) and N-allylthiourea, against the template molecules diphenyl phosphate, 15 triethyl phosphate and trimethyl phosphate. A cross-interference study between phosphate, nitrate 16 and sulfate was carried out for the MIP materials using an inductance, capacitance and resistance 17 (LCR) meter. Capacitance measurements were taken applying an alternating current (AC) with a 18 potential difference of 1 V root mean square (RMS) at a frequency of 1 kHz. The cross-interference 19 study demonstrated a strong binding preference to phosphate over the other nutrient salts tested 20 for each formulation. The size of template molecule and length of the functional monomer side 21 groups also determined that a combination of a short chain functional monomer in combination 22 with a template containing large R-groups produced the optimal binding site conditions when 23 synthesising a phosphate selective MIP. 24