3D-Printed Device for Efficient Packing of Semisolid Samples in 3.2-mm Rotors Used in Cryoprobe Systems.

We present a compact, 3D-printed device designed to facilitate the efficient packing of semisolid or highly viscous samples into 3.2-mm rotors compatible with cryogenic solid-state NMR probes. The tool enables sample loading by centrifugation under standard laboratory conditions, significantly improving packing reproducibility and minimizing sample loss. In contrast to previously reported designs for conventional rotors, this device is optimized for the expanded volume and geometrical constraints of 90-μL rotors used in the Bruker CPMAS cryoprobe. A complementary unloading tool is also described to recover samples or enable rotor reuse. Both tools are compatible with standard benchtop centrifuges and are fully customizable. Their implementation improves sample handling for biological or material samples with limited availability or challenging rheological properties. Open-access 3D design files are provided to support broad adoption and future adaptation to other rotor sizes or sample formats. These devices represent a scalable solution for routine use and may inspire further development of customized tools for challenging sample types.