Susceptibility cancellation of a microcoil wound with a paramagnetic-liquid-filled copper capillary

[Display omitted] •A microcoil wound with a copper capillary is presented.•Paramagnetic liquid is supplied inside the capillary.•Paramagnetic liquid cancels the susceptibility effect of the coil.•Liquid flow inside the capillary cools the coil and the circuit. Even though microcoils improve the sensitivity of NMR measurement of tiny samples, magnetic-field inhomogeneity due to the bulk susceptibility effect of the coil material can cause serious resonance-line broadening. Here, we propose to fabricate the microcoil using a thin, hollow copper capillary instead of a wire and fill paramagnetic liquid inside the capillary, so as to cancel the diamagnetic contribution of the copper. Susceptibility cancellation is demonstrated using aqueous solution of NiSO4. In addition, the paramagnetic liquid serves as coolant when it is circulated through the copper capillary, effectively transferring the heat generated by radiofrequency pulses.