Majorana fermion (MF) whose antiparticle is itself has been predicted in condensed matter systems. Signatures of the MFs have been reported as zero energy modes in various systems. More definitive evidences associated with MF's novel properties are highly desired to verify the existence of the MF. Very recently, theory has predicted MFs to induce spin selective Andreev reflection (SSAR), a novel magnetic property which can be used to detect the MFs. Here we report the first observation of the SSAR from MFs inside vortices in Bi 2 Te 3 /NbSe 2 hetero-structure, in which topological superconductivity was previously established. By using spin-polarized scanning tunneling

A rapidly formed supramolecular polypeptide-DNA hydrogel was prepared and used for in situ multilayer three-dimensional bioprinting for the first time. By alternative deposition of two complementary bio-inks, designed structures can be printed. Based on their healing properties and high mechanical strengths, the printed structures are geometrically uniform without boundaries and can keep their shapes up to the millimeter scale without collapse. 3D cell printing was demonstrated to fabricate live-cell-containing structures with normal cellular functions. Together with the unique properties of biocompatibility, permeability, and biodegradability, the hydrogel becomes an ideal biomaterial for 3D bioprinting to produce designable 3D constructs for applications in tissue engineering.

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The incorporation of molecular switches in organic structures is of great interest in the chemical design of stimuli-responsive materials that mimic the complex functions of living systems. Merocyanine dyes that convert to spiropyran moieties upon exposure to visible light have been extensively studied as they can be incorporated in hydrated covalent networks that will expel water when this conversion occurs and induce a volumetric shrinkage. We report here on a sulfonate-based water-soluble photoswitch that, in contrast to the well-known systems, triggers a volumetric expansion in hydrogels upon exposure to photons. Contraction is in turn observed under dark conditions in a highly reversible manner. The novel behavior of the photoswitch incorporated in the covalent network was predicted by coarse-grained simulations of the system’s chemical structure. Using pH control and polymeric structures that differ in lower critical solution temperature, we were able to develop hydrogels with highly tunable volumetric expansion. The novel molecular function of the systems developed here led to materials with the negative phototaxis observed in plants and could expand the potential use of hydrogels as sensors, soft robots, and actuators.