NMRduino

Many students, researchers and hobbyists will be familiar with the open-source-electronics ecosystem “Arduino”, which provides an extraordinarily simple way to interface sensors (or other input devices) and actuators (output) with logic programs, e.g. C code, to create a wide variety of standalone control devices termed embedded systems. An NMR spectrometer can be regarded as one specific type of embedded system: the output is a magnetic field produced by a coil, the input is a magnetic field (detected and recorded by a digitizer), and a pulse programmer keeps timing and data in order.

The “NMRduino” is a magnetic resonance spectrometer based on (but we must stress, not endorsed or supported by) Arduino that we have developed over recent years to study hyperpolarized NMR systems, NMR relaxation, high-resolution spectroscopy, and coherent control at low magnetic fields, as well as teach basic principles of magnetic resonance to student beginners

Main features are:

1. Compact, plug-and-play hardware. A credit-card-sized circuit board contains all electronic components and connects to any laptop, desktop or raspberry Pi computer via USB. Includes pulse programmer and analog sampling up to 100 kHz.
2. Transparent, intuitive control interface. User-specific pulse sequences (2 us time resolution) can be written to control both DC and AC magnetic fields up to several hundred kHz. Open access to low-level programming interface for advanced users.
3. Flexibility. Can be connected to conventional rf-inductive pickup coils, or alternative sensors such as atomic magnetometers.

Use in recent research:

1. Real-time nuclear spin polarimetry of hyperpolarized liquids. We have used NMRduino to non-destructively quantify nuclear spin polarization of hyperpolarized spin tracers (e.g. [1-13C]-pyruvate) used in NMR and in vivo MRI [1]. In a background field of ~30 nT we use a high sensitivity 87Rb magnetometer to measure the field generated by the sample (<1 nT), as it is driven by a windowed dynamical decoupling pulse sequence that both maximizes the nuclear spin lifetime (T1 = 25 s) and modulates polarization for easy detection.
2. Hyperpolarization of 13C spins in small molecules via adiabatic level crossings. NMRduino can produce DC field sweeps for parahydrogen-induced polarization in microtesla fields.
3. Fast-field cycling NMR. NMRduino has been used to study of spin dynamics photo-CIDNP, porous materials[2], scalar relaxation pathways[3] in liquid-state samples over magnetic fields of nT to 100 mT.
4. Wide error-tolerant excitation in low-field NMR and benchmarking of an original class of DC composite pulses. NMRduino shows that so-called “meridional composite pulses” [4] perform with high-fidelity using rudimentary coils, opening a path to ultra-portable and inexpensive NMR systems, useful “in the field” or in education.

References:

[1] Mouloudakis et al., Real time polarimetry of hyperpolarized 13C nuclear spins using an atomic magnetometer, The Journal of Physical Chemistry Letters 14, 1192-1197 (2023). https://doi.org/10.1021/acs.jpclett.2c03864
[2] Bodenstedt et al., Fast-field-cycling ultralow-field nuclear magnetic relaxation dispersion Nature Communications 12, 4041 (2021) https://doi.org/10.1038/s41467-021-24248-9
[3] Bodenstedt et al., Decoupling of spin decoherence paths near zero magnetic field, The Journal of Physical Chemistry Letters 13, 98 (2022) https://doi.org/10.1021/acs.jpclett.1c03714
[4] Bodenstedt et al., Meridional composite pulses for low-field magnetic resonance, Physical Review A 106, 033102 (2022) https://doi.org/10.1103/PhysRevA.106.033102