Current in vitro anti-tumor drug screening strategies are insufficiently portrayed lacking true perfusion and draining microcirculation systems, which may post significant limitation in reproducing the transport kinetics of cancer therapeutics explicitly. Herein, we report the fabrication of an improved tumor model consisting of bioprinted hollow blood vessel and lymphatic vessel pair, hosted in a threedimensional (3D) tumor microenvironment-mimetic hydrogel matrix, termed as the tumor-on-a-chip with bioprinted blood and lymphatic vessel pair (TOC-BBL). The bioprinted blood vessel was perfusable channel with opening on both ends while the bioprinted lymphatic vessel was blinded on one end, both of which were embedded in a hydrogel tumor mass, with vessel permeability individually tunable through optimization of the composition of the bioinks. We demonstrated that systems with different combinations of these bioprinted blood/lymphatic vessels exhibited varying levels of diffusion profiles for biomolecules and anti-cancer drugs. Our TOC-BBL platform mimicking the natural pathway of drug-tumor interactions would have the drug introduced through the perfusable blood vessel, cross the vascular wall into the tumor tissue via diffusion, and eventually drained into the lymphatic vessel along with the carrier flow. Our results suggested that this unique in vitro tumor model containing the bioprinted blood/lymphatic vessel pair may have the capacity of simulating the complex transport mechanisms of certain pharmaceutical compounds inside the tumor microenvironment, potentially providing improved accuracy in future cancer drug screening.

efficient/controllable photoexcited charge separation. [1,2] So far, the most commonly investigated SFPO is based on BiFeO 3 , [1,3] but its bandgap of ≈2.7 eV is not low enough to absorb the full spectrum of the visible light. The real potential of SFPO in photovoltaic applications significantly drives the exploring of new perovskite oxides with efficient visible light absorption. Recently, the realization of defect-driven-ferroelectricity and low bandgap states (even down to ≈1.1 eV) in perovskites (KNbO 3 ) 1−x (BaNi 1/2 Nb 1/2 O 3−δ ) x (KN-BNN) suggests that ferroelectricity and low bandgap can be simultaneously achieved by compositional modification. With two different transition-metal cations at the B-site in highly oxygen-vacancytolerable perovskite oxides, one cation (Nb 5+ ) provides off-center distortion and polarization, and the other (Ni 2+ ) decreases the difference in electronegativity within the perovskite BO bonds to create electronic states in the gap. The leaky conductivity associated with accommodation of Ni 2+ -oxygen vacancy combinations results in the loss of piezoelectricity especially at room temperature, which is generally the case for simple perovskite oxides. [4] Efforts have been taken to improve the tolerance of oxygen vacancies in order to keep the ferroelectricity, such as modifying the amount of BaNi 1/2 Nb 1/2 O 3−d (BNN) in the solid solution in order to decrease the concentration of oxygen vacancies, i.e., 0.98KN-0.02BNN, and 0.65PbTiO [5,6] or using more complex perovskite oxides with layered structure LaCoO 3 -mediated BiTiO 3 (E g = 2.65 eV). [7] However, an effective strategy to achieve an appropriate balance between the defect-induced low bandgap and defect-induced electrically leaky ferroelectricity is still currently lacking. Following the defect-engineered strategy, we present an efficient route to change the generally negative role of oxygen vacancies to be piezoelectrically/ferroelectrically friendly. Guided by the point-defect mediated large piezoelectricity in ferroelectric crystals, [8] defect-dipoles formed by dopant-oxygen vacancy pairs are preferentially coupled with the strong spontaneous polarization from host according to general symmetry-conforming property of point defects. [9][10][11] Moreover, both experiments and theoretical calculations provide strong evidence that the dopant-oxygen obtain low bandgap (i.e., 1.1-3.8 eV), the electrically leaky perovskite oxides generally lose piezoelectricity mainly due to oxygen vacancies. Therefore, the development of highly piezoelectric ferroelectric semiconductor remains challenging. Here, inspired by point-defect-mediated large piezoelectricity in ferroelectrics especially at the morphotropic phase boundary (MPB) region, an efficient strategy is proposed by judiciously introducing the gap states at the MPB where defect-induced local polar heterogeneities are thermodynamically coupled with the host polarization to simultaneously achieve high piezoelectricity and low bandgap. A concrete example, Ni 2+ -mediated (1...

The thermal-electric performance of Bi2O2Se can be significantly improved by application of tensile strain and the Bi2O2Se monolayer has great potential as thermoelectric (TE) material.

Hematite (Fe 2 O 3 ) is a well-known oxide semiconductor suitable for photoelectrochemical (PEC) water splitting and industry gas sensing. It is widely known that Sn doping of Fe 2 O 3 can enhance the device performance, yet the underlying mechanism remains elusive. In this work, we determine the relationship between electronic structure, optical properties, and PEC activity of Sn-doped Fe 2 O 3 by studying highly crystalline, wellcontrolled thin films prepared by pulsed laser deposition (PLD). We show that Sn doping substantially increases the n-type conductivity of Fe 2 O 3 , and the conduction mechanism is better described by a small-polaron hopping (SPH) model. Only 0.2% Sn doping significantly reduces the activation energy barrier for SPH conduction from at least 0.5 eV for undoped Fe 2 O 3 to 0.14 eV for doped ones. A combination of X-ray photoemission, X-ray absorption spectroscopy, and DFT calculations reveals that the Fermi level gradually shifts toward the conduction band minimum with Sn doping. A localized Fe 2+ -like gap state is observed at the top of the valence band, accounting for the SPH conduction. Interestingly, different from the literature, only 0.2% Sn doping in Fe 2 O 3 significantly improves the PEC activity, while more Sn decreases it. The improved PEC activity is partially attributed to an increased band bending potential which facilitates the charge separation at the space charge region. The reduced activation energy barrier for SPH will facilitate the transport of photoexcited carriers for the enhanced PEC, which is of interest for further carrier dynamics study.

An equiatomic TiZrHfMoNb high-entropy alloy (HEA) was developed as a solar thermal energy storage material due to its outstanding performance of hydrogen absorption. The TiZrHfMoNb alloy transforms from a body-centered cubic (BCC) structure to a face-centered cubic (FCC) structure during hydrogen absorption and can reversibly transform back to the BCC structure after hydrogen desorption. The theoretical calculations demonstrated that before hydrogenation, the BCC structure for the alloy has more stable energy than the FCC structure while the FCC structure is preferred after hydrogenation. The outstanding hydrogen absorption of the reversible single-phase transformation during the hydrogen absorption–desorption cycle improves the hydrogen recycling rate and the energy efficiency, which indicates that the TiZrHfMoNb alloy could be an excellent candidate for solar thermal energy storage.

No abstract

For traditional piezoelectric sensors based on poled ceramics, a low curie temperature (Tc) is a fatal flaw due to the depolarization phenomenon. However, in this study, we find the low Tc would be a benefit for flexible piezoelectric sensors because small alterations of force trigger large changes in polarization. BaTi0.88Sn0.12O3 (BTS) with high piezoelectric coefficient and low Tc close to human body temperature is taken as an example for materials of this kind. Continuous piezoelectric BTS films were deposited on the flexible glass fiber fabrics (GFF), self-powered sensors based on the ultra-thin, superflexible, and polarization-free BTS-GFF/PVDF composite piezoelectric films are used for human motion sensing. In the low force region (1–9 N), the sensors have the outstanding performance with voltage sensitivity of 1.23 V N−1 and current sensitivity of 41.0 nA N−1. The BTS-GFF/PVDF sensors can be used to detect the tiny forces of falling water drops, finger joint motion, tiny surface deformation, and fatigue driving with high sensitivity. This work provides a new paradigm for the preparation of superflexible, highly sensitive and wearable self-powered piezoelectric sensors, and this kind of sensors will have a broad application prospect in the fields of medical rehabilitation, human motion monitoring, and intelligent robot.

Transparent ferroelectrics, with promising prospects in transparent optoelectronic devices, have unique advantages in self-powered photodetection. The self-powered photodetectors based on the photovoltaic effect have quicker responses and higher stability compared with those based on the pyroelectric effect. However, the ferroelectric ceramics previously applied are always opaque and have no infrared light-stimulated photovoltaic effect. Thus, it would be very meaningful to design photodetectors based on infrared light-stimulated photovoltaic effect and/or transparent ferroelectric ceramics. In this work, highly optical transparent pristine lead lanthanum zirconate titanate (PLZT) and band gap-engineered Ni-doped PLZT ceramics with excellent piezoelectric/ferroelectric properties were prepared by hot-pressing sintering. Stable and excellent photovoltaic performance was obtained for pristine PLZT and band gap-engineered PLZT. The value of short-circuit current density is at least 2 orders of magnitude larger than those in PLZT reported in previous works. The transparent PLZT and Ni-doped PLZT ferroelectric ceramics are applied as self-powered photodetectors for the first time for 405 nm and near-infrared light, respectively. The devices based on PLZT under 405 nm light exhibit high detectivity (7.15 × 10 7 Jones) and quick response (9.5 ms for rise and 11.5 ms for decay), and those devices based on Ni-doped PLZT, under near-infrared light filtered from AM 1.5 G simulated sunlight, also exhibit high detectivity (6.86 × 10 7 Jones) and short response time (8.5 ms), both presenting great potential for future transparent photodetectors.