Resonances in ultracold collisions involving heavy molecules are difficult to understand, and have proven challenging to detect. Here we report the observation of magnetically tunable Feshbach resonances in ultracold collisions between 23 Na 40 K molecules in the rovibrational ground state and 40 K atoms. We prepare the atoms and molecules in various hyperfine levels of their ground states and observe the loss of molecules as a function of the magnetic field. The atommolecule Feshbach resonances are identified by observing an enhancement of the loss rate coefficients. We have observed three resonances at approximately 101 G in various atom-molecule scattering channels, with the widths being a few hundred milliGauss. The observed atom-molecule Feshbach resonances at ultralow temperatures probe the three-body potential energy surface with an unprecedented resolution. Our work will help to improve the understanding of complicated ultracold collisions, and open up the possibility of creating ultracold triatomic molecules.Understanding collisions involving molecules at the quantum level has been a long-standing goal in chemical physics [1]. Scattering resonance is one of the most remarkable quantum phenomena and plays a critically important role in the study of collisions. It is very sensitive to both the long-range and short-range parts of the molecule interaction potential, and thus offers a unique probe of the potential energy surface (PES) governing the collision dynamics. Although scattering resonances are well known and have been the main features in ultracold atomic gases and nuclear collisions [2], they have proven challenging to observe in molecule systems. Recently, significant progress has been achieved in experimentally studying resonances in cold molecular collisions involving the light particles, e.g., H 2 , HD molecule or He atom, by means of molecular beam techniques. In the crossed-beam or merged-beam experiments, shape resonances or Feshbach resonances have been observed in atom-molecule chemical reactions [3][4][5][6][7][8], atom-molecule inelastic collisions [9][10][11], and molecule-molecule inelas- * These authors contributed equally to this work. tic collisions [12,13]. However, in these experiments, the collision energies are still high (at Kelvin or sub Kelvin), and thus a few partial waves contribute to the scattering cross sections.Ultracold molecules offer great opportunities to study molecular collisions in the quantum regime. At ultralow temperatures, the de Broglie wavelength of the collision partners is much larger than the range of molecular interaction potential, and only the lowest possible partial wave dominates the collision process [14,15]. Consequently, the collisions at ultracold temperatures are highly quantum mechanical. Due to the anisotropy of the PES, the collisions involving ultracold molecules may support many resonances that are contributed by the rotational and vibrational excited states [16,17]. Therefore, it is expected that scattering resonances can be routinely obse...

Over the past few decades, there has been an increasing interest in the fabrication of complex high-resolution three-dimensional (3D) architectures at micro/nanoscale. These architectures can be obtained through conventional microfabrication methods including photolithography, electron-beam lithography, femtosecond laser lithography, nanoimprint lithography, etc. However, the applications of these fabrication methods are limited by their high costs, the generation of various chemical wastes, and their insufficient ability to create high-aspect-ratio 3D structures. High-resolution 3D printing has recently emerged as a promising solution, as it is capable of building multifunctional 3D constructs with optimal properties. Here we present a review on the principles and the recent advances of high-resolution 3D printing techniques, including two-photon polymerization (TPP), projection microstereoLithography (PµSL), direct ink writing (DIW) and electrohydrodynamic printing (EHDP). We also highlight their typical applications in various fields such as metamaterials, energy storage, flexible electronics, microscale tissue engineering scaffolds and organ-on-chips. Finally, we discuss the challenge and perspective of these high-resolution 3D printing techniques in technical and application aspects. We believe that high-resolution 3D printing will eventually revolutionize the microfabrication processes of 3D architectures with high product quality and diversified materials. It will also find applications in a wide scope.

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