This paper aims to obtain an analytical expression for the ratio of unloading work of indentation (Wu) to total loading work of indentation (Wt) (work recovery ratio of indentation) in instrumented spherical indentation. The expanding cavity model and Lamé solution are used. Three typical stress–strain relations (elastic-perfectly plastic, linear hardening, and power-law hardening) are analyzed. The results of finite-element method coincide with the expressions. The expressions show that the work recovery ratio of indentation is just related to plastic parameters. Furthermore, elastic work (We) are obtained, and it is proved that We should be distinguished from Wu in spherical indentation.

All-polymer solar cells composed of binary blends of donor poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b]thiophene-)-2–6-diyl)] (PBDTTT-CT ), and acceptor polymers naphthalene diimide-selenophene copolymer (PNDIS-HD) and perylene diimide-selenophene copolymer (PPDIS) had power conversion efficiencies (PCEs) of 1.3 and 2.1%, respectively. Ternary blend solar cells composed of [PBDTTT-CT][PNDIS-HD]1−x[PPDIS]x at 75 wt% PPDIS had a PCE of 3.2%, which is about a 50%–140% enhancement compared with the binary blend devices. Equality of the ternary blend short-circuit current to the sum of those of the binary blend devices, among other results, provided evidence of a parallel-like bulk heterojunction mechanism in the ternary blend solar cells. These results provide the first example of enhanced performance in ternary blend all-polymer solar cells.

More than two decades of III-N materials research has led to the production of visible spectrum commercial light-emitting diodes (LEDs) and laser diodes (LDs). Commercial c-plane LEDs are currently limited by efficiency droop which describes the decline in efficiency with increasing input current density. Laser-based sources, however, provide peak efficiencies at much higher current densities and may circumvent efficiency droop limitations. The potential benefits of non-basal plane (NBP) orientations could accelerate the evolution of solid-state lighting from LED to LD sources. Here, we review the progress in long-wavelength (440–590 nm) NBP quantum well LD research and discuss applications in solid-state lighting, visible light communication and smart lighting.

This paper presents experimental results supporting a theory that electric fields accelerate the growth of tin (Sn) whiskers. We have rapidly (within one week) grown long (~100 µm) and dense (~300 mm−2) whiskers on thin Sn films. Humidity and an applied electric field are found to have a strong effect when applied together, making whiskers orders of magnitude longer and denser. An evidence of explosive whisker development is presented.

The remarkable optoelectronic and especially photovoltaic performance of hybrid organic–inorganic perovskite (HOIP) materials drives efforts to connect materials properties to this performance. From nano-indentation experiments on solution-grown single crystals we obtain elastic modulus and nano-hardness values of APbX3 (A = Cs, CH3NH3; X = I, Br). The Young's moduli are ~14, 19.5, and 16 GPa, for CH3NH3PbI3, CH3NH3PbBr3, and CsPbBr3, respectively, lending credence to theoretically calculated values. We discuss the possible relevance of our results to suggested “self-healing”, ion diffusion, and ease of manufacturing. Using our results, together with literature data on elastic moduli, we classified HOIPs amongst the relevant material groups, based on their elastomechanical properties.

The separation of oil–water mixtures is a widely utilized unit operation, used for handling a wide variety of mixtures from industry including: petroleum drilling and refining, fracking, waste-water treatment, mining, metal fabrication and machining, textile and leather processing, and rendering. Membrane-based methods have become increasingly attractive for the separation of oil–water mixtures because they are relatively energy-efficient, can be readily used to separate a variety of industrial feed streams, and provide consistent permeate quality. In this perspective, we discuss the design strategies for membranes with selective wettability i.e., membranes that are either selectively wet by, or prevent wetting by, the oil or water phase. The design strategies include the parameterization of two important physical characteristics: the surface porosity and the breakthrough pressure. We also discuss how they are related for membranes with a periodic geometry. On the basis of this understanding, we explore principles that allow for the systematic design of membranes with selective wettability. A review of the current literature on the separation of oil–water mixtures using membranes with differing wettabilities is also presented. Finally, we conclude by discussing the current challenges and outlook for the future of the field.

We report the use of electrospray to continuously deposit thin films, including patterned films, of a block copolymer (BCP). High substrate temperatures led to vertically oriented cylindrical microdomains at the film surface independent of the solvent composition and deposition rates utilized. Conversely, low substrate temperatures resulted in morphologies that were more sensitive to these parameters, with poorly ordered films of globular structures observed at the lowest temperatures considered. The deposition pattern is defined by spatially varying the electric field at the substrate using an underlying charged grid. These results open up new possibilities for patterned deposition of BCP films with morphological control.

A model with which to predict the effect of coplanar electrode geometry on diffraction uniformity in photorefractive polymer display devices was developed. Assumptions made in the standard use cases are no longer valid in the regions of extreme electric fields present in this type of device. Using electric-field induced second-harmonic generation through multiphoton microscopy, the physical response in regions of internal electric fields which fall outside the standard regimes of validity were probed. Adjustments to the standard model were made and the results of the new model corroborated through holographic four-wave mixing measurements.

Beyond the traditional phase conversion or biphase mixing hybrid, we developed the dilute magnesium-doped wollastonite inks and three-dimensional (3D) printing approaches to fabricate the ultrahigh strength bioceramic porous scaffolds. The mechanical strength (>120 MPa) of the porous bioceramics was an order of magnitude higher than the pure wollastonite and other stoichiometric Ca–Mg silicate porous bioceramics. This abnormal but expected improvement in strength in bioceramic scaffolds is equivalent or even superior to the mechanical requirement in load-bearing bone defects. The breakthrough is totally unexpected, and it quickly opens the door for the 3D printing bioceramics manufacture and large-area segmental bone defect repair applications.

We demonstrate the fabrication by anodization of niobium oxide microcones, several microns long, from aqueous solutions of 1 wt% hydrogen fluoride (HF) with varied sodium fluoride (NaF) concentration (0–1 M). Raman spectroscopy and x-ray diffractometer analysis revealed the as-grown microcones to be crystalline Nb2O5−x with preferred (1 0 0) and (0 1 0) orientations. The overall Nb2O5−x formation rate increased with the increasing NaF concentration, and structures as tall as 20 μm were achieved in just 20 min of anodization at 1 M NaF. Rapid formation of niobia microcones was even observed in the absence of HF at this NaF concentration. Photocatalytic activity for water oxidation was highest for microcones grown under the highest NaF concentration.

We detail the influence of tapered interfaces on the nanoscale morphologies of ion-doped poly(styrene-b-oligo-oxyethylene methacrylate) block polymers (BPs). Most significantly, the location of double-gyroid network phase window was found in ion-doped normal-tapered materials, and a similar window was not detectable in the corresponding non-tapered and inverse-tapered BPs. Additionally, the effective interaction parameters, χeff, were reduced substantially in the tapered materials in comparison with their non-tapered counterparts. Overall, this work demonstrates that tapering between polymer blocks provides unique control over BP morphologies and improves the material processability (due to lower χeff), potentially facilitating the development of future ion-conducting devices.

A correction method for linear hardening materials is brought forward to obtain the true (or nearly true) modulus of cylindrical specimens with middle aspect ratios in compression tests. By considering the stress concentration near the interface between the specimen and the compression platen caused by slanted contact, a “sandwich” model is developed. A correction formula is derived and all parameters can be obtained from the tested stress–strain curve. Experiments were performed on Al 2024 specimens with four aspect ratios. The corrected results are closer to the intrinsic modulus than the tested values, which verify the effectiveness of the correction method.

Micromechanical testing of electroplated gold alloy films has been conducted using theta-like specimens. Specimens were formed by a standard combination of photolithography, electroplating, and deep reactive ion etching. Testing was performed using an instrumented indenter and the results interpreted using a finite-element model with a Ramberg–Osgood constitutive law to extract elastic and plastic material properties. The observed results were highly repeatable and appear to be sensitive to variations in both sample dimensions and material properties. These qualities suggest that the testing methodology may have significant value as a quality control technique in the fabrication of metal microelectromechanical systems.

Electronically active block polymers based on π-conjugated macromolecules have been investigated for applications where nanostructured electrodes are of prime import; however, controlling the nanoscale order of these materials has proven challenging. Here, we demonstrate that diblock copolymers that utilize a non-conjugated radical polymer moiety as the electronically active block assemble into ordered thin-film nanostructures. Specifically, the diblock copolymer polydimethylsiloxane-b-poly(2,2,6,6-tetramethylpiperidinyloxy methacrylate) (PDMS–PTMA) was synthesized via atom transfer radical polymerization to generate polymers with readily controlled molecular properties. Importantly, solvent annealing of the PDMS–PTMA thin films led to well-defined nanostructures with domain spacings of the order of ~30–40 nm.

Screen-printed organic electrochemical transistors (OECTs) were tested as glucose and lactate sensors. The intrinsic amplification of the device allowed it to detect metabolites in low molecular range and validation tests were made on real human sweat. The development of an organically modified sol–gel solid electrolyte paves the way for all printed OECT-based biosensors.

The emergence of methyl-ammonium lead halide (MAPbX3) perovskites motivates the identification of unique properties giving rise to exceptional bulk transport properties, and identifying future materials with similar properties. Here, we propose that this “defect tolerance” emerges from fundamental electronic-structure properties, including the orbital character of the conduction and valence band extrema, the charge-carrier effective masses, and the static dielectric constant. We use MaterialsProject.org searches and detailed electronic-structure calculations to demonstrate these properties in other materials than MAPbX3. This framework of materials discovery may be applied more broadly, to accelerate discovery of new semiconductors based on emerging understanding of recent successes.