Universities across the U.S. have moved to various virtual teaching models in response to the health threats caused by the COVID-19 pandemic. When converting to an online-only mode, STEM and related fields face additional challenges over the lab portion of courses because laboratory courses and active-learning projects frequently require specialized equipment and manual dexterity interactions. In this paper, we report the results of a study on students’ perceptions about online learning during the initial phase of the pandemic at a public university in California, U.S. We focus on the overall reaction to the rapid conversion to online, the negative impressions created, “structural” concerns that would be difficult to mitigate, concerns readily amenable to mitigation, and side effects such as impact on equity. Twenty-five recommendations for those factors deemed improvable are provided.

Croconic acid (CA) is the first organic ferroelectric with a spontaneous polarity in bulk samples comparable to its inorganic counterparts. As a natural extension of study, ultrathin CA films (similar to nm scale) were investigated to reveal ferroelectric effects in films on different substrates for their fundamental and industrial significance. However, the void defect at the interface between the film and substrate is presumed to interfere with surface effects. In this work, a non-invasive technique, a slow positron beam, coupled with Doppler broadening energy spectroscopy (DBES), is applied to study the void defects within the interfacial layer between CA films and Si and SiO2 substrates. The effect of external electric field on defect formation is also investigated and an underlying mechanism is proposed.y

The NSF-CREST Center for Advanced, Functional Materials, CAFM, at California State University San Bernardino (CSUSB) has greatly increased the number of quality research opportunities for undergraduates from multiple institutions, at multiple sites. At the same time, this project promotes research advancement in materials science well beyond what was pursued before CAFM. In this chapter we overview how we used the new CAFM Center and CREST funds to maximize opportunities for undergraduate research (UR), in a new interdisciplinary area, including evaluation of the UR experiences. The program builds on other successful projects by various members of the team, including early research experiences funded by the NSF PRISM program, more focused research funded previously by DoD and NASA, and the growing impact of our campus Office of Student Research.

Recent advances provide new opportunities in the field of polymer piezoelectric materials. Piezoelectric materials provide unique insights to the fundamental understanding of the solid state. In addition, piezoelectric materials have a wide range of applications, representing billions of dollars of commercial applications. However, inorganic piezoelectric materials have limitations that polymer ferroelectric materials can overcome, if certain challenges can be addressed. This mini-review is a practical summary of the current research and future directions in the investigation and application of piezoelectric materials with an emphasis on polymeric piezoelectric materials. We will assume that the reader is well versed in the subject of polymers, but not as familiar with piezoelectric materials. (c) 2018 Society of Chemical Industry

A novel method for fabricating ultra-thin croconic acid (CA) films with a very low surface roughness on Si wafers is reported. With a thickness of approximately 20 nm and surface roughness of +/- 2.0 nm, the film obtained far exceeds the quality and smoothness of previously reported CA thin films. The film is prepared by applying a high electric field in situ during thermal vapor deposition, promoting alignment of the CA molecules due to their high dipole moment. The result is compared with that of the best-reported film produced via a combination of thermal evaporation at low substrate temperature with subsequent slow heating, to demonstrate the greatly enhanced uniformness of the film. In addition, the film's ferroelectric behavior is demonstrated using piezoresponse force microscopy measurements. A mechanism for film formation under electric field assisted deposition is proposed. (C) 2017 Elsevier B.V. All rights reserved.

We are implementing a materials genome strategy to discover or create new organic advanced functional materials. We are most interested in ferroelectric, piezoelectric and related properties. The three main components of the research are theory, synthesis, and measurement. The two main thrusts of the theory component are first-principles calculations, and data mining of archives such as the Cambridge Crystallographic Database (CCD) for organic compounds of interest. Novel formulations, including thin films, and new co-crystals of known electroactive organic components are also being investigated. Organic chemistry has historically not been as concerned with the electrical and mechanical properties of organic structures. This gives substantial weight to functional properties as a guide to the synthetic approach. Using this approach, we have identified several candidates. Of these, we have been able to successfully identify two new organic materials, both with electromechanical responses.

Croconic acid is the first single molecular organic ferroelectric material exhibiting very high spontaneous polarization (~ 20 μC/cm2) at room temperature. Maximizing polarization depends on minimizing void defects in croconic acid crystals. In this experiment, the change in void defects upon the thermal treatment is characterized using positron annihilation lifetime spectroscopy. Both defect void size and intensity are measured, and their dependence upon the thermal treatment duration is studied. In addition, the relation between the void defect and ferroelectric hysteresis of croconic acid is established.

Hodge's formulization of the Tool-Narayanaswamy-Moynihan (TNM) equation from the Adam-Gibbs (AG) theory was re-evaluated. The non-linearity parameter (x) and the apparent activation energy (Δh*) of the TMN equation were re-derived. Compared with the original derivations, the revised values of x and Δh* were better correlated with experimental results. Of particular importance, the revised theoretical x correctly predicts the experimental trend of x for the cooling rate of polystyrene, whereas the original derivation predicted an opposite trend. Furthermore, the new derivation establishes a strong relationship between the fragility coefficient (m) and the x of a material. The relationship correlates well with the experimental values for a wide range of materials. Ultimately, the revised equations for x and Δh* more precisely reveal the theoretical foundation of the phenomenological TNM equation, as it relates to structural relaxation of polymeric materials.

Morphing wing technologies provide expanded functionality in piloted and robotic aircraft, extending particular vehicle mission parameters as well as increasing the role of aviation in both military and civilian applications. However, realizing control surfaces that do not void the benefits of morphing wings presents challenges that can be addressed with microfiber composite actuators (MFCs). We present two approaches for realizing control surfaces. In one approach, flap-like structures are formed by bonding MFCs to each side of a metal substrate. In the other approach, MFCs are bonded directly to the wing. Counter intuitively, the flap approach resulted in larger voltage actuation curvatures, with increased mass load. Actuation performance, defined as the ratio of curvature per applied voltage, was as large as 5.8±0.2×10−4 (kV·mm) −1 . The direct bonding approach reveals that at zero wing pressure, up to 63±3 μ m of displacement could be realized.

The structure and cooperative proton ordering of two-dimensional sheets of croconic acid were studied with scanning tunneling microscopy and first-principles calculations. Unlike in the crystalline form, which exhibits a pleated, densely packed polar sheet structure, the confinement of the molecules to the surface results in hydrogen-bonded chiral clusters and networks. First-principles calculations suggest that the surface stabilizes networks of configurational isomers, which arise from direct hydrogen transfer between their constituent croconic acid monomers. Some of these configurations have a net polarization. It is demonstrated through constrained molecular dynamics simulations that simultaneous proton transfer between any two molecules can occur spontaneously. This finding is a prerequisite for the occurrence of in-plane ferroelectricity based on proton transfer in 2D sheets. DOI: 10.1103/PhysRevB.87.041402

Many low-dimensional systems, such as nanoscale islands, thin films, and multilayers, as well as bulk systems, such as multiferroics, are characterized by the lack of inversion symmetry, a fact that may give rise to a Dzyaloshinskii-Moriya (DM) interaction. For sufficient strength, the DM interaction will favor spiral spin configurations of definite chirality. In order to harness such systems for applications, it is important to understand the conditions under which these spiral spin configurations form and how they can be controlled via an external field. Here, we present exact solutions of the 1D magnetization profiles in such systems for arbitrary material parameters in closed form. Determining the energy per unit length exactly, we are able to present the critical strength of the DM interaction, at which spiral solutions are energetically favorable. These magnetization profiles, in general, take the form of a domain wall or soliton lattice, with all solitons having the same chirality, whose sign is dictated by DM interaction. Conversely, given an energetically favorable spiral solution, we determine quantitatively how the magnetization profile changes as a function of the applied field.

This paper documents an experimental and theoretical investigation into characterizing the mechanical configurations and performances of THUNDER actuators, a type of piezoelectric actuator known for their large actuation displacements, through fabrication, measurements and finite element analysis. Five groups of such actuators with different dimensions were fabricated using identical fabrication parameters. The as-fabricated arched configurations, resulting from the thermo-mechanical mismatch among the constituent layers, and their actuation performances were characterized using an experimental set-up based on a laser displacement sensor and through numerical simulations with ANSYS, a widely used commercial software program for finite element analysis. This investigation shows that the presence of large residual stresses within the piezoelectric ceramic layer, built up during the fabrication process, leads to significant nonlinear electromechanical coupling in the actuator response to the driving electric voltage, and it is this nonlinear coupling that is responsible for the large actuation displacements. Furthermore, the severity of the residual stresses, and thus the nonlinearity, increases with increasing substrate/piezoelectric thickness ratio and, to a lesser extent, with decreasing in-plane dimensions of the piezoelectric layer.