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Karl Heinrich Schneider,Benjamin J. Goldberg,Onur Hasturk,Xuan Mu,Marvin Dötzlhofer,Gabriela Eder,Sophia Theodossiou,Luis Pichelkastner,Peter Riess,Sabrina Rohringer,Herbert Kiss,Andreas H. Teuschl‑Wo 한국생체재료학회 2023 생체재료학회지 Vol.27 No.00
Background There is a great clinical need and it remains a challenge to develop artificial soft tissue constructs that can mimic the biomechanical properties and bioactivity of natural tissue. This is partly due to the lack of suitable biomaterials. Hydrogels made from human placenta offer high bioactivity and represent a potential solution to create animal-free 3D bioprinting systems that are both sustainable and acceptable, as placenta is widely considered medical waste. A combination with silk and gelatin polymers can bridge the biomechanical limitations of human placenta chorion extracellular matrix hydrogels (hpcECM) while maintaining their excellent bioactivity. Method In this study, silk fibroin (SF) and tyramine-substituted gelatin (G-TA) were enzymatically crosslinked with human placental extracellular matrix (hpcECM) to produce silk-gelatin-ECM composite hydrogels (SGE) with tunable mechanical properties, preserved elasticity, and bioactive functions. The SGE composite hydrogels were characterized in terms of gelation kinetics, protein folding, and bioactivity. The cyto- and biocompatibility of the SGE composite was determined by in vitro cell culture and subcutaneous implantation in a rat model, respectively. The most cell-supportive SGE formulation was then used for 3-dimensional (3D) bioprinting that induced chemical crosslinking during extrusion. Conclusion Addition of G-TA improved the mechanical properties of the SGE composite hydrogels and inhibited crystallization and subsequent stiffening of SF for up to one month. SGE hydrogels exhibit improved and tunable biomechanical properties and high bioactivity for encapsulated cells. In addition, its use as a bioink for 3D bioprinting with free reversible embedding of suspended hydrogels (FRESH) has been validated, opening the possibility to fabricate highly complex scaffolds for artificial soft tissue constructs with natural biomechanics in future.
Atomic-scale sensing of the magnetic dipolar field from single atoms
Choi, Taeyoung,Paul, William,Rolf-Pissarczyk, Steffen,Macdonald, Andrew J.,Natterer, Fabian D.,Yang, Kai,Willke, Philip,Lutz, Christopher P.,Heinrich, Andreas J. Nature Publishing Group, a division of Macmillan P 2017 Nature nanotechnology Vol.12 No.5
<P>Spin resonance provides the high-energy resolution needed to determine biological and material structures by sensing weak magnetic interactions(1). In recent years, there have been notable achievements in detecting(2) and coherently controlling(3-7) individual atomic-scale spin centres for sensitive local magnetometry(8-10). However, positioning the spin sensor and characterizing spin-spin interactions with sub-nanometre precision have remained outstanding challenges(11,12). Here, we use individual Fe atoms as an electron spin resonance (ESR) sensor in a scanning tunnelling microscope to measure the magnetic field emanating from nearby spins with atomic-scale precision. On artificially built assemblies of magnetic atoms (Fe and Co) on a magnesium oxide surface, we measure that the interaction energy between the ESR sensor and an adatom shows an inverse-cube distance dependence (r(-3.01+/-0.04)). This demonstrates that the atoms are predominantly coupled by the magnetic dipole-dipole interaction, which, according to our observations, dominates for atom separations greater than 1 nm. This dipolar sensor can determine the magnetic moments of individual adatoms with high accuracy. The achieved atomic-scale spatial resolution in remote sensing of spins may ultimately allow the structural imaging of individual magnetic molecules, nanostructures and spin-labelled biomolecules.</P>
Home-built sub-Kelvin scanning tunneling microscope with electron spin resonance capability
Jiyoon Hwang,Denis Krylov,Taehong Ahn,Lei Fang,Kyungju Noh,Andreas J. Heinrich,Yujeong Bae 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1
Scanning tunneling microscopy is a powerful tool to characterize the electronic and magnetic properties of atomic scale structures on a surface. Recent advances in increasing energy resolutions have been achieved functionalizing the STM tip by a well-characterized molecule [1,2] or integrating electron spin resonance with STM (ESR-STM) [3]. We present the design and performance of home-built STM with high frequency cabling, which is incorporated with a Joule-Thomson refrigerator and 2-axes vector magnets. Applying high frequency (microwave) electric fields to the STM junction through 50 Ohm coaxial cables causes significant loss of insertion power due to the impedance mismatch at the STM junction of ~1 GOhm, which limits the frequency range of applicable microwaves. To overcome this limitation, we introduced a microwave antenna and terminated the cable at 50 Ohm. Applying microwaves to the antenna rather than the STM tip allows us to reduce the formation of standing waves as well as to increase the transmission. Our work shows using the specially designed mechanical damper and optimizing the electrical noise levels provide the outstanding performance of STM for the single atom ESR experiment.
Jisoo Yu,Franklin H. Cho,Luciano Colazzo,Yejin Jeong,Juyoung Park,Junjie Liu,Arzhang Ardavan,Giovanni Boero,Andreas J. Heinrich,Fabio Donati 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1
Electron spin resonance (ESR) spectroscopy is a powerful tool for establishing the quantum coherence of molecular spin qubits [1]. In order to determine their performance as quantum bits for quantum information processing, it is important to integrate them into solid-state substrates and characterize their interaction with the electrons of the substrate. However, this characterization requires tailored spectrometers with sufficient surface sensitivity. Here, we utilize α, γ-bisdiphenylene-β-phenylallyl (BDPA) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) thin film as samples to characterize a home-built surface-sensitive ESR spectrometer. Both molecules are traditional standards in the ESR technique and have different characteristics on the surfaces [2], [3]. The spectrometer operates in the X band (10 GHz) in both continuous wave and pulsed mode in a wide range of temperature (2.5-300 K) and magnetic field (0-3.2 T). To maximize the microwave field in a 2D spin system, we developed a coplanar-type resonator, on whose surface we deposited the molecular films. We demonstrate a spin sensitivity of 1012 spins / G · √Hz in continuous wave mode at room temperature, allowing ESR measurements down to a single layer of molecular spins.
Reading and writing single-atom magnets
Natterer, Fabian D.,Yang, Kai,Paul, William,Willke, Philip,Choi, Taeyoung,Greber, Thomas,Heinrich, Andreas J.,Lutz, Christopher P. Macmillan Publishers Limited, part of Springer Nat 2017 Nature Vol.543 No.7644
<P>The single-atom bit represents the ultimate limit of the classical approach to high-density magnetic storage media. So far, the smallest individually addressable bistable magnetic bits have consisted of 3-12 atoms(1-3). Long magnetic relaxation times have been demonstrated for single lanthanide atoms in molecular magnets(4-12), for lanthanides diluted in bulk crystals(13), and recently for ensembles of holmium (Ho) atoms supported on magnesium oxide (MgO)(14). These experiments suggest a path towards data storage at the atomic limit, but the way in which individual magnetic centres are accessed remains unclear. Here we demonstrate the reading and writing of the magnetism of individual Ho atoms on MgO, and show that they independently retain their magnetic information over many hours. We read the Ho states using tunnel magnetoresistance(15,16) and write the states with current pulses using a scanning tunnelling microscope. The magnetic origin of the long-lived states is confirmed by single-atom electron spin resonance(17) on a nearby iron sensor atom, which also shows that Ho has a large out-of-plane moment of 10.1 +/- 0.1 Bohr magnetons on this surface. To demonstrate independent reading and writing, we built an atomic-scale structure with two Ho bits, to which we write the four possible states and which we read out both magnetoresistively and remotely by electron spin resonance. The high magnetic stability combined with electrical reading and writing shows that single-atom magnetic memory is indeed possible.</P>
Electrically controlled nuclear polarization of individual atoms
Yang, Kai,Willke, Philip,Bae, Yujeong,Ferró,n, Alejandro,Lado, Jose L.,Ardavan, Arzhang,Ferná,ndez-Rossier, Joaquí,n,Heinrich, Andreas J.,Lutz, Christopher P. Nature Publishing Group 2018 Nature nanotechnology Vol.13 No.12
Single atomic spin sensing of magnetic interactions in a tunnel junction
Jinkyung Kim,Won-jun Jang,Thi Hong Bui,Deung-Jang Choi,Christoph Wolf,Fernando Delgado,Yi Chen,Denis Krylov,Soonhyeong Lee,Sangwon Yoon,Christopher P. Lutz,Andreas J. Heinrich,Yujeong Bae 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1
Single spins are widely regarded as a leading candidate for realizing next-generation quantum devices for sensing and quantum information processing. Detection and coherent control of single spins require to localize single spins and characterize its magnetic surroundings. Scanning tunneling microscopy in combination with electron spin resonance (ESR-STM) technique [1] enables a direct access to the quantum states of single magnetic atoms or molecules on surfaces. Using ESR-STM, we investigated spin resonance of hydrogenated Ti (TiH) atoms adsorbed on bridge binding site of MgO in a two-dimensional vector magnetic field. Here, the spin 1/2 TiH atom with no magnetic anisotropy was employed as a probe of magnetic environments at the tunnel junction. We found both ESR frequency and amplitude change as a function of the angle of vector magnetic fields. The resonance frequency varied by different vector magnetic fields indicates an anisotropy of the g-factor, resulting from the variation of angular momentum contributions due to the crystal fields. We developed a stereoscopic way to unravel the g-factor along the three principal axes. Moreover, ESR amplitude dependence on the direction of magnetic fields provides the further understanding of ESR mechanisms, which results from two factors, tunneling magnetoresistance (TMR) effect at the spin-polarized STM junction and the transverse magnetic field to drive ESR. Our results will enable to predict ESR active spin centers on different substrates as well as in other quantum-nanoscience platforms.
Hyperfine interaction of individual atoms on a surface
Willke, Philip,Bae, Yujeong,Yang, Kai,Lado, Jose L.,Ferró,n, Alejandro,Choi, Taeyoung,Ardavan, Arzhang,Ferná,ndez-Rossier, Joaquí,n,Heinrich, Andreas J.,Lutz, Christopher P. American Association for the Advancement of Scienc 2018 Science Vol.362 No.6412
<P>Taking advantage of nuclear spins for electronic structure analysis, magnetic resonance imaging, and quantum devices hinges on knowledge and control of the surrounding atomic-scale environment. We measured and manipulated the hyperfine interaction of individual iron and titanium atoms placed on a magnesium oxide surface by using spin-polarized scanning tunneling microscopy in combination with single-atom electron spin resonance. Using atom manipulation to move single atoms, we found that the hyperfine interaction strongly depended on the binding configuration of the atom. We could extract atom-and position-dependent information about the electronic ground state, the state mixing with neighboring atoms, and properties of the nuclear spin. Thus, the hyperfine spectrum becomes a powerful probe of the chemical environment of individual atoms and nanostructures.</P>