Single-Chip Dynamic Nuclear Polarization Microsystem

Abstract

Integration of the sensitivity-relevant electronics of nuclear magnetic resonance (NMR) and electron spin resonance (ESR) spectrometers on a single chip is a promising approach to improve the limit of detection, especially for samples in the nanoliter and subnanoliter range. Here, we demonstrate the cointegration on a single silicon chip of the front-end electronics of NMR and ESR detectors. The excitation/detection planar spiral microcoils of the NMR and ESR detectors are concentric and interrogate the same sample volume. This combination of sensors allows one to perform dynamic nuclear polarization (DNP) experiments using a single-chip-integrated microsystem having an area of about 2 mm2. In particular, we report 1H DNP-enhanced NMR experiments on liquid samples having a volume of about 1 nL performed at 10.7 GHz­(ESR)/16 MHz­(NMR). NMR enhancements as large as 50 are achieved on TEMPOL/H2O solutions at room temperature. The use of state-of-the-art submicrometer integrated circuit technologies should allow the future extension of the single-chip DNP microsystem approach proposed here up the THz­(ESR)/GHz­(NMR) region, corresponding to the strongest static magnetic fields currently available. Particularly interesting is the possibility to create arrays of such sensors for parallel DNP-enhanced NMR spectroscopy of nanoliter and subnanoliter samples.

Microfluidic Overhauser DNP Chip for Signal-enhanced Compact NMR

“…ADF5610), and Anders et al 43 have demonstrated a CMOS chip oscillator reaching 14 GHz that yields sufficient power for the EPR excitation of a 200 µl sample, and enough sensitivity for detection. Very recently the Boero group 44 presented a CMOS based single-chip DNP system for experiments inside an electromagnet. The authors conclude that employing an all planar topology is limited in terms of NMR excitation homogeneity and confirm that the pronounced EM coupling between the MW and RF resonant structures in their setup represents a major technical challenge.…”

Recent advances in microfluidics-based bioNMR analysis

“…, DNP) to overcome this limitation. 49,93,94 DNP was first proposed by Albert Overhauser, 95 which can transfer the large magnetic moment of electron spins under microwave (MW) irradiation to nuclear spins and thus enhance the NMR signal intensity by up to 2 orders of magnitude. 96 To explore the feasibility of Overhauser DNP (ODNP) for improving the sensitivity of a low-field NMR system, Korvink and co-workers developed a miniaturized probe head (including a MW resonator, a microfluidic chip, electrical shims and an RF transceiver coil) mounted inside a palm-sized permanent magnet (Fig.…”

Challenges and Advances in the Application of Dynamic Nuclear Polarization to Liquid-State NMR Spectroscopy

“…Planar microcoils are easier to fabricate down to nL volumes and find applications in on-chip NMR devices . Recently, Sahin Solmaz et al have demonstrated a silicon-chip-based device for DNP NMR of aqueous solutions of the TEMPO radical at room temperature . A sample volume of about 1 nL is contained in a capillary that is placed over the double NMR/EPR microcoils.…”