Wearable biosensors are critical for enabling real-time and continuous health monitoring and disease management.

Geothermal energy offers the potential to provide continuous baseload renewable energy. Unlike conventional geothermal approaches, emerging closed-loop geothermal can employ specialized fluids that improve thermal energy recovery and expand the range of applications. However, the requirements for candidate fluids are challenging. The fluids must be physically and chemically stable under high-temperature, -pressure, and -shear conditions. Their effective heat capacity must be high and their viscosity must also be low, factors that motivated us to use a high-latent heat phase change material within a low-viscosity carrying fluid. Here, we prepare the microencapsulated phase change material-based slurries (PCSs) and perform a comprehensive thermal and hydrodynamic characterization to assess their suitability for use in a closed-loop geothermal operation. The thermophysical properties of the PCSs show promising results with minimal change in onset temperature (2.14 °C) and low supercooling (2.21 °C) during charging and discharging, respectively. A suitably low viscosity (in the range 0.01–0.05 Pa·s at 300 s–1) could be obtained with PCS concentrations in the range 20–30 wt %. Higher concentrations resulted in higher viscosities that would incur pumping energy costs exceeding the potential thermal storage benefits. At 30 wt % PCM, this fluid offers the potential for approximately 30% more stored energy than water alone for the 80 °C system. With respect to robustness under combined thermal and shear stresses, a PCS with 30 wt % phase change material showed no visible separation ratio and no shell rupturing or chemical changes when cycled 10× from 20 to 80 °C while being sheared at operation-relevant rates of 10–300 s–1. This study delineates and de-risks PCSs as geo-fluids, exploiting both sensible and latent heat storage with physical and chemical stability.

The complexation of Mg II with adenosine 5'-triphosphate (ATP) is omnipresent in biochemical energy conversion, but is difficult to interrogate directly. Here we use the spin-1 = 2 β-emitter 31 Mg to study Mg II -ATP complexation in 1-ethyl-3methylimidazolium acetate (EMIM-Ac) solutions using β-radiation-detected nuclear magnetic resonance (β-NMR). We demonstrate that (nuclear) spin-polarized 31 Mg, following ion-implantation from an accelerator beamline into EMIM-Ac, binds to ATP within its radioactive lifetime before depolarizing. The evolution of the spectra with solute concentration indicates that the implanted 31 Mg initially bind to the solvent acetate anions, whereafter they undergo dynamic exchange and form either a mono-( 31 Mg-ATP) or di-nuclear ( 31 MgMg-ATP) complex. The chemical shift of 31 Mg-ATP is observed up-field of 31 MgMg-ATP, in accord with quantum chemical calculations. These observations constitute a crucial advance towards using β-NMR to probe chemistry and biochemistry in solution.

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