In this work, a poly-Si0.35Ge0.65 microelectromechanical systems (MEMS)- based actuator was designed and fabricated using a CMOS compatible standard process to specifically strain a bi-layered (2L) MoS2 flake and measure its electrical properties. Experimental results of the MEMS-TMDC device show an increase of conductivity up to three orders of magnitude by means of vertical actuation using the substrate as the body terminal. A force balance model of the MEMS-TMDC was used to determine the amount of strain induced in the MoS2 flake. Strains as high as 3.3% is reported using the model fitted to the experimental data.

This work presents the synthesis of selenium-based nanoparticles via microwave-assisted heating and their subsequent characterization using UV-vis Spectroscopy (UV-Vis), high-resolution transmission electron microscopy (HRTEM), and energy-dispersive X-ray spectroscopy (EDX), techniques. Ongoing research includes the study of the nanoparticles capacity to generate reactive oxygen species (ROS).

Sintered tape-cast yttria-stabilized zirconia (YSZ) was evaluated for its elemental composition, crystal structure, and imaged with atomic force microscopy (AFM) and scanning electron microscopy (SEM). Human bone marrow stem cells (hBMSC) were cultured on the ceramic and differentiated into the osteoblast lineage; alkaline phosphatase (ALP) activity was tracked as a differentiation marker. The YSZ was composed of purely tetragonal grains with a median equivalent circular diameter of 283 nm. Zirconium, yttrium, oxygen, and adventitious carbon was detected on the substrate with no other elements in significant quantities detected. YSZ samples had an RMS roughness value of 27 nm, elastic modulus of 206 ± 14 GPa, and hardness of 14 ± 2 GPa. hBMSC were observed to attach and proliferate on the YSZ surfaces and had significantly increased ALP versus the undifferentiated control cultured on glass. This method for producing a YSZ ceramic yields a typical material of this type and supports attachment and differentiation of hBMSC; thus, making it useful as a bone implant material.

The patterning of gold and silver micro and nanostructures on rigid and flexible substrates is investigated by microcontact printed thiol based self-assembled monolayers. The aspect ratio of the noble metal micro and nanostructures is determined by interaction of the -SH head group of the CH3(CH2)19SH molecules and the surface of the noble metal. Silver micro and nanostructures with >10 times higher aspect ratios can be realized in comparison to commonly realized gold micro and nanostructures. The printing process is described, and the etching process is characterized in terms of etching window and etching selectivity. Potential electronic and photonic applications of the micro and nanostructures are discussed taking the boundary conditions of the printing process and the selected material system into consideration.

Based on wettability and reaction interfaces previously reported, as well as on thermodynamic considerations, a likely mechanism has been proposed for the chemical interaction taking place at the metal/ceramic interface during wettability experiments carried out by the so-called “sessile drop” method. The experiments involved three Ag-Cu-based brazing alloys [Cusil (Ag-28wt.%Cu), Cusil-ABA (Ag-34.6wt.%Cu-1.58wt.%Ti) and Incusil-ABA (Ag-26.6wt.%Cu-12.4wt.%In-0.89wt.%Ti)] and as polished and pre-oxidized pressure-less sintered silicon carbide (PLS-SiC), with a total holding time of 90 minutes at 850 °C, under a Zr sponge-gettered vacuum of 10-4/10-5 Torr.

Polyurea resins derived from tolyldiisocyante (TDI) and a reactive solvent-free nanofluid (NF-NH2) surface-decorated with propylamines can be tuned over three to five orders of magnitude in storage modulus (10 MPa to 10 GPa) and hardness modulus (6 kPa to 4 GPa) by varying weight fractions of components. The thermal properties of this NF-NH2 are similar to several other nanofluids reported using the same bulky anionic counterion that also imparts liquidity in the absence of any solvent. This tuning suggests applications ranging from opaque protective coatings to clearcoats to sealants to adhesives.

Tactile sense provides us with the necessary information and feedback to determined tasks. Within this context, haptic devices represent a growing and highly interesting field to be included in biomedical devices, teleoperation applications, and video games. These devices are usually developed with rigid materials, motors, and mechanisms to provide tactile feedback to individuals that corresponds to a defined task, producing pressure, tangential force or vibrations as stimuli on the skin. Here, we present a prototype of a soft pneumatic haptic device based on an inflatable hyperelastic membrane, that can provide two stimuli over skin such as pression and traction with only one input of energy. The device was fabricated using different types of silicone materials and membrane shapes. This exhibits experimentally a maximum vertical deformation of 13 mm and a tangential displacement of 10 mm at 7 kPa. These two mechanically programmed movements open the possibility of using this technology in mechano-tactile feedback for wearable devices, with low-cost hardware, soft interaction between devices and skin, and lightweight.

The research of high-performance flexible supercapacitors is urgent due to the rapid development of wearable and portable electronics. The key challenge is the preparation of flexible electrodes with high areal capacitance since electrodes are the most important part of supercapacitors. Compared to those conventional electrodes loading with typical flexible substrates such as textile, PET, paper et al, free-standing electrodes have many advantages such as more efficient capacity contribution, solidly embedded active materials and thinner thickness. Herein, we have successfully fabricated a novel sandwich-like structure free-standing MoO3-rGO (reduced graphene oxide) composite film electrode for flexible supercapacitors using simple vacuum filtration method followed by HI reduction process. The obtained MoO3-rGO composite film electrode shows excellent electrochemical performance, whose areal specific capacitance reaches 8972 mF·cm-2 (1.5 mA·cm-2). Here, MoO3 provides pseudocapacitance and rGO provides double-layer capacitance. After cycling for 2000 cycles, the capacity retention is 86.7%, showing good cycle stability. Besides, the as-prepared composite film has good flexibility and will not break easily during following bending, rolling, folding or twisting steps. This study has been approved to be an important step for the high-performance electrode design for free-standing flexible supercapacitors.

Amorphous Si (a-Si) is used for fabrication of commercial low-cost flat panel image detectors for radiographic applications such as computed tomography (CT) imaging. a-Si photodiodes are known to exhibit a rapid decrease in quantum efficiency near 750nm. While crystalline Si does not suffer from such an early decline, the large-area and low-cost constraints of medical imagers make it challenging and costly to use crystalline Si for such devices. In this work, we report on the development of a sensitive layer for upconversion from 785 nm to green region of the spectrum, which nearly matches the peak quantum efficiency of a-Si detectors. Various host materials have been extensively studied in literature with rare earth ions such as Er3+(emission: green+red), Tm3+(emission: blue), Ho3+(emission: red+green) along with Yb3+ as a sensitizer for upconversion to the visible regime at high incident optical power (∼100 mW) for colloidal solutions. We carried out a thermal decomposition synthesis of NaYF4:Yb(18%),Er(2%),Gd(15%) at moderate temperature (∼320°C), resulting in a nearly pure hexagonal phase material. This is confirmed by powder X-ray diffraction (PXRD) of the unannealed sample with a lattice constant (∼5.17 Å). High-resolution transmission electron microscopy (HRTEM) measurements reveal the formation of nearly spherical nanoparticles. The observed plane ([100]) inferred from lattice fringes in TEM data with a visibly estimated interplanar distance (4.4±1.6 Å) is in reasonable agreement with standard data (∼5.17 Å) for comparable NaYF4-based materials. Excitation (785 nm) of the deposited thin films of Gd-doped unannealed material at relatively low incident power (∼0.4 mW) exhibits a PL response in green (539 nm) and red (665 nm) region of the spectrum. Gd-based upconversion material based thin films are thus a feasible photonic material for potential effective extension of high quantum efficiency range in a-Si for flat panel image detectors.

Organic light emitting diodes (OLEDs) have drawn great attention owing to their potential applications in high-quality flat display panels and smart solid-state lighting. Over the last three decades, numerous approaches have been made on material design and device physics to achieve high-efficiency and long-lifespan. Herein, we report a novel tactic to employ solution-processed hybrid metal oxide, molybdenum trioxide-tungsten trioxide (MoO3:WO3), as an efficient and stable hole injection/transport (HIL/HTL) and electron blocking layer for efficient OLEDs. By using phosphorescent orange-red emitter tris(2-phenylquinoline)-iridium(III) Ir(2-phq)3, MoO3:WO3 HIL based OLED device exhibits a power efficiency of 27.7 lm W-1 and 22.9 lm W-1 at 100 and 1000 cd m-2, respectively, which are 89% and 157% higher than that of conventional OLED device consisting of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) as an HIL. Moreover, the resulted device also displays 1.6 times lower turn-on voltage and 3.0 time higher brightness as compare to other counter part. The higher device performances of OLED device may be attributed to robust hole transporting ability, balanced charge carrier in the recombination zone and non-acidic nature of designed HIL. Our results demonstrate that a novel alternative approach based on transition metal oxide hybrid HIL/HTL as a substitute to PEDOT:PSS for high-efficiency solution process OLEDs.

Here we present the results of the exciton states study in WSe2 and MoS2 monolayers. Thin WSe2 and MoS2 films obtained by CVD technique were studied by optical methods. The films two-dimensionality and homogeneity were confirmed by the methods of atomic force microscopy and luminescence spectroscopy. The second harmonic generation (SHG) spectroscopy technique was used for the exciton states study at room temperature in the pump photon energy range of 0.8-1.05 eV. The sevenfold SHG intensity resonance amplification was found for the 1.62 eV and 1.87 eV SHG photon energy for the WSe2 and MoS2 films, respectively, that corresponds to the exciton transition energy. These resonance peaks belong to optical A excitons with 1s energy level.

The degradation of organic molecules in an aqueous medium using heterogeneous photocatalysis depends on the chemical composition and concentration of the organic compound, the crystalline and morphological nature of the photocatalyst, the pH of the dye dilution, and the reaction temperature. Since photocatalytic degradation is a process that occurs on the surface of the catalytic material, it is desirable to induce maximum adsorption of the organic compound. One strategy to achieve this is to functionalize the surface of the catalyst to retain the molecule of interest. In this work, we studied the interaction of acid orange 7 (AO7) with commercial TiO2-anatase powder catalyst, and with a catalyst synthesized in house using titanium tetrachloride and ethanolamine (TiO2-et). Our results indicate that there is no adsorption of the AO7 dye on the TiO2-et particles. The infrared spectrum of the TiO2-et particles is presented.

The implantation and controlled release of growth factors can enhance the proliferation and differentiation of cells that promote new bone formation at defect sites. Therefore, chitosan polymer microspheres were prepared by the water-in-oil emulsion (W/O) method and solvent freeze-drying, using glutaraldehyde as an ionic crosslinker, along with the lyophilization of solvents, to microencapsulate growth factors, preventing denaturation. The microspheres were loaded with recombinant bone morphogenetic protein 2 (Rh-BMP-2). They were spherical in shape, with a rough surface ranging in particle size from 0.4 to 1.6 μm. The yield percentage with respect to the polymer was 70% and the BMP-2 load was regulated by the initial protein dose. BMP-2 release experiments were performed for 7 days in PBS solutions at pH 4 and 7.4. The results showed that the protein release rate was only 2% lower at pH 7.4. BMP-2/chitosan microspheres were compatible with the MG-63 cell line (ATCC®CRL-1427™Homo sapiens bone osteosarcoma) and could be considered drug delivery vehicles in bone tissue engineering applications.