Yizhan Wang

Bio: Yizhan Wang is an academic researcher from University of Wisconsin-Madison. The author has contributed to research in topics: Piezoelectricity & Oxygen evolution. The author has an hindex of 9, co-authored 18 publications receiving 343 citations.

Wafer-scale heterostructured piezoelectric bio-organic thin films

Abstract: Piezoelectric biomaterials are intrinsically suitable for coupling mechanical and electrical energy in biological systems to achieve in vivo real-time sensing, actuation, and electricity generation. However, the inability to synthesize and align the piezoelectric phase at a large scale remains a roadblock toward practical applications. We present a wafer-scale approach to creating piezoelectric biomaterial thin films based on γ-glycine crystals. The thin film has a sandwich structure, where a crystalline glycine layer self-assembles and automatically aligns between two polyvinyl alcohol (PVA) thin films. The heterostructured glycine-PVA films exhibit piezoelectric coefficients of 5.3 picocoulombs per newton or 157.5 × 10-3 volt meters per newton and nearly an order of magnitude enhancement of the mechanical flexibility compared with pure glycine crystals. With its natural compatibility and degradability in physiological environments, glycine-PVA films may enable the development of transient implantable electromechanical devices.

Self-Activated Electrical Stimulation for Effective Hair Regeneration via a Wearable Omnidirectional Pulse Generator.

Abstract: Hair loss, a common and distressing symptom, has been plaguing humans. Various pharmacological and nonpharmacological treatments have been widely studied to achieve the desired effect for hair regeneration. As a nonpharmacological physical approach, physiologically appropriate alternating electric field plays a key role in the field of regenerative tissue engineering. Here, a universal motion-activated and wearable electric stimulation device that can effectively promote hair regeneration via random body motions was designed. Significantly facilitated hair regeneration results were obtained from Sprague-Dawley rats and nude mice. Higher hair follicle density and longer hair shaft length were observed on Sprague-Dawley rats when the device was employed compared to conventional pharmacological treatments. The device can also improve the secretion of vascular endothelial growth factor and keratinocyte growth factor and thereby alleviate hair keratin disorder, increase the number of hair follicles, and promote hair regeneration on genetically defective nude mice. This work provides an effective hair regeneration strategy in the context of a nonpharmacological self-powered wearable electronic device.

Two-dimensional nonlayered materials for electrocatalysis

Abstract: Creating two-dimensional (2D) geometry from nonlayered catalytic materials may significantly advance electrocatalyst design. The 2D morphology of three-dimensional lattices (2D nonlayered materials) offer large structural distortions, massive surface dangling bonds, and coordinated-unsaturated surface atoms, which can induce high surface chemical activity and promote the chemisorption of reactants and fast interfacial charge transfer, thereby enhancing the electrocatalytic performance. In this article, we review typical strategies for structural engineering and manipulation of electronic states to enable the unique electrocatalytic advantages of 2D nonlayered materials. An overview is presented on recent research advances in the development of 2D nonlayered materials for catalyzing the representative electrochemical reactions that are essential to energy and sustainability, including hydrogen evolution, oxygen evolution, oxygen reduction, and CO2 reduction. For each type of redox reactions, their unique catalytic performance and underlying mechanism are discussed. Important achievements and key challenges are also discussed.

Implanted Battery-Free Direct-Current Micro-Power Supply from in Vivo Breath Energy Harvesting.

Abstract: In vivo biomechanical energy harvesting by implanted nanogenerators (i-NGs) is promising for self-powered implantable medical devices (IMDs). One critical challenge to reach practical applications is the requirement of continuous direct-current (dc) output, while the low-frequency body activities typically generate discrete electrical pulses. Here, we developed an ultrastretchable micrograting i-NG system that could function as a battery-free dc micro-power supply. Packaged by a soft silicone elastomer with a cavity design, the i-NG exhibited an ultralow Young’s modulus of ∼45 kPa and a high biocompatibility to soft biological tissues. The i-NG was implanted inside the abdominal cavity of Sprague Dawley adult rats and directly converted the slow diaphragm movement during normal respiration into a high-frequency alternative current electrical output, which was readily transmitted into a continuous ∼2.2 V dc output after being integrated with a basic electrical circuit. A light-emitting diode was constantly...

Manipulating the ion-transfer kinetics and interface stability for high-performance zinc metal anodes

Abstract: The zinc metal is recognized as one of the most promising anodes for Zn-based batteries in an energy-storage system. However, the deposition and transfer of bivalent Zn2+ into the host structure suffer from sluggish kinetics accompanying the side-reactions at the interface. Herein, we report a new class of Zn anodes modified by a three-dimensional (3D) nanoporous ZnO architecture coating on a Zn plate (designated as Zn@ZnO-3D) prepared by in situ Zn(OH)42− deposition onto the surface. This novel structure has been proven to accelerate the kinetics of Zn2+ transfer and deposition via the electrostatic attraction toward Zn2+ rather than the hydrated one in the electrical double layer. As a consequence, it achieves an average 99.55% Zn utilization and long-time stability for 1000 cycles. Meanwhile, the Zn@ZnO-3D/MnO2 cell shows no capacity fading after 500 cycles at 0.5 A g−1 with a specific capacity of 212.9 mA h g−1. We believe that the mechanistic insight into the kinetics and thermodynamic properties of the Zn metal and the understanding of structure–interface–function relationships are very useful for other metal anodes in aqueous systems.

Interfacial design of dendrite‐free zinc anodes for aqueous zinc‐ion batteries

Abstract: Aqueous zinc-ion batteries have rapidly developed recently as promising energy storage devices in large-scale energy storage systems owing to their low cost and high safety. Research on suppressing zinc dendrite growth has meanwhile attracted widespread attention to improve the lifespan and reversibility of batteries. Herein, design methods for dendrite-free zinc anodes and their internal mechanisms are reviewed from the perspective of optimizing the host-zinc interface and the zinc-electrolyte interface. Furthermore, a design strategy is proposed to homogenize zinc deposition by regulating the interfacial electric field and ion distribution during zinc nucleation and growth. This Minireview can offer potential directions for the rational design of dendrite-free zinc anodes employed in aqueous zinc-ion batteries.

Dendrites in Zn-Based Batteries.

Abstract: Aqueous Zn batteries that provide a synergistic integration of absolute safety and high energy density have been considered as highly promising energy-storage systems for powering electronics. Despite the rapid progress made in developing high-performance cathodes and electrolytes, the underestimated but non-negligible dendrites of Zn anode have been observed to shorten battery lifespan. Herein, this dendrite issue in Zn anodes, with regard to fundamentals, protection strategies, characterization techniques, and theoretical simulations, is systematically discussed. An overall comparison between the Zn dendrite and its Li and Al counterparts, to highlight their differences in both origin and topology, is given. Subsequently, in-depth clarifications of the specific influence factors of Zn dendrites, including the accumulation effect and the cathode loading mass (a distinct factor for laboratory studies and practical applications) are presented. Recent advances in Zn dendrite protection are then comprehensively summarized and categorized to generate an overview of respective superiorities and limitations of various strategies. Accordingly, theoretical computations and advanced characterization approaches are introduced as mechanism guidelines and measurement criteria for dendrite suppression, respectively. The concluding section emphasizes future challenges in addressing the Zn dendrite issue and potential approaches to further promoting the lifespan of Zn batteries.

Chemistry of materials

Abstract: I am really glad to have this opportunity to write to you, specially about a subject in which I have worked for half a century. When I was your age, if somebody had told me that I would be working in chemistry of materials most of my life, I would not have believed it. At that time, chemistry of materials meant studying something about cement, steel, sand and asbestos. It was indeed dull. I never didwell in school and college exams on questions related to this subject. Much later in my life, I got greatly interested in the subject for various reasons. First, inmy study of chemistry, I was influenced by Linus Pauling who ismy academic grandfather. His book titled ‘Nature of the Chemical Bond’ which I read when I was young made a great impression. It taught me how the structure of molecules and materials is an extremely important aspect of chemistry, and how the understanding of structure and bonding provides a basis to understand chemistry and to do new chemistry. It is because of this terrific inspiration that I started studying chemistry. It was clear at the end of my undergraduate career that I wanted to be a chemist.

Challenges in the material and structural design of zinc anode towards high-performance aqueous zinc-ion batteries

Abstract: Rechargeable aqueous metal-ion batteries are very promising as alternative energy storage devices during the post-lithium-ion era because of their green and safe inherent features. Among the different aqueous metal-ion batteries, aqueous zinc-ion batteries (ZIBs) have recently been studied extensively due to their unique and outstanding benefits that hold promise for large-scale power storage systems. However, zinc anode problems in ZIBs, such as zinc dendrites and side reactions, severely shorten the ZIB's cycle lifetime, thus restricting their practical application. Here, we sum up in detail the recent progress on general strategies to suppress zinc dendrites and zinc anode side reactions based on advanced materials and structure design, including the modification of the planar zinc electrode surface layer, internal structural optimization of the zinc bulk electrode, modification of the electrolyte and construction of the multifunctional separator. The various functional materials, structures and battery efficiencies are discussed. Finally, the challenges for ZIBs are identified in the production of functional zinc anodes.