Rapid Electromechanical Transduction on a Single-Walled Carbon Nanotube Film: Sensing Fast Mechanical Loading via Detection of Electrical Signal Change

Carbon nanotubes (CNTs) have been widely explored as next generation embedded-strain-pressure sensors. However, most investigations of CNT sensors did not consider the response time as a critical factor, although the ultrafast sensing of mechanical deformation is very important for the detection of dynamic loading or impact, such as in reactive armor systems. Owing to the low capacitance that shortens the response time of the electrical resistance changes induced by mechanical deformation, CNTs are expected to detect rapid electromechanical transduction without delay. Herein, we fabricate single-walled carbon nanotube (SWNT) films on diverse substrates, and evaluate their applications as sensors to detect rapid electromechanical transduction on a macroscopic scale. Under repetitive, high-speed mechanical loading, the SWNT films generate consistent electrical signal changes, which are accurately synchronized with their strain and the beginning of the deformation

Spontaneous Biomacromolecule Absorption and Long-Term Release by Graphene Oxide

Biomacromolecule loading is the popular research in the biomedical field. To control the loading amount and releasing profile, various materials and fabrication techniques were developed. In this study, layer-by-layer assembly of multilayer films between collagen (Col) and graphene oxide (GO) was used to control the release of the loading molecule. By mixing GO into the system, ovalbumin (OVA) can be spontaneously adsorbed onto the GO sheet (denoted as GO/OVA) via the hydrophobic interaction. Two kinds of multilayer films (Col/GO/OVA and Col/GO/OVA) were fabricated. The thickness growth curve, quantitative of each layer adsorption, film morphology, stability, cell viability, and OVA release from multilayer films were investigated. The result has shown excellent film stability, macromolecule loading, and sustained release because of GO ability

Hollow Capsules of Reduced Graphene Oxide Nanosheets Assembled on a Sacrificial Colloidal Particle

We introduce a novel and versatile approach for preparing hollow multilayer capsules of graphene oxide nanosheets. Positively charged reduced graphene oxide (rGO-NH₃⁺) and negatively charged reduced graphene oxide (rGO-COO⁻) were used as building blocks for the layer-by-layer assembly of graphene multilayer films onto polystyrene (PS) colloids. After removing the PS colloids with THF treatment, hollow graphene capsules with necessary physical and chemical stabilities were prepared successfully. Furthermore, we expand this approach in incorporating a new functionality such as gold nanoparticles into a hollow graphene capsule. SEM and TEM analyses suggest the successful preparation of multilayers of hollow graphene capsules and integration of gold nanoparticles into a hollow graphene capsule

Multilayered Controlled Drug Release Silk Fibroin Nanofilm by Manipulating Secondary Structure

Many studies of drug delivery nanoplatforms have explored drug loading affinity and controlled release. The nanoplatforms can be influenced by their inherent building blocks. Natural polypeptide silk fibroin (SF) is an excellent nanoplatform material because of its high biocompatibility and unique structural properties. SF secondary structures have different properties that can be changed by external stimuli. Thus, the characterization of SF-containing platforms is strongly affected by secondary structure transformations. Structural changes can occur spontaneously, which hinders the control of structural variation in aqueous conditions. Herein, we successfully prepared a controllable secondary structure composed of SF/heparin (HEP) layer-by-layer assembled nanofilms using simple solvents (glycerol and methanol). SF in the SF/HEP nanofilms takes up than 90%, which means configurations of SF have a strong effect on the character of the nanofilms. We investigated the degradation profiles of SF/HEP nanofilms depending on their β-sheet contents and demonstrated an immediate correlation between the transformation of secondary structures inside the nanofilms and the degree of degradation of nanofilms. Finally, SF/HEP nanofilms were used as a delivery platform for incorporating the anticancer drug epirubicin (EPI). We could control the loading efficiency and release profile of EPI with various β-sheet contents of the nanofilms

Sustained Nitric Oxide-Providing Small Molecule and Precise Release Behavior Study for Glaucoma Treatment

Incidence ofglaucoma, a severe disease leading to irreversible loss of vision, is increasing with global aging populations. Lowering intraocular pressure (IOP) is the only proven treatment method for glaucoma. Nitric oxide (NO) is an emerging material targeting the conventional outflow pathway by relaxing the trabecular meshwork (TM). However, there is little understanding on the NO level effective in IOP lowering without toxicity. Here, we report a novel long-term NO-releasing polydiazeniumdiolate (NOP) that enables lowering IOP via the conventional outflow pathway. NOP is composed of carbon-bound polydiazeniumdiolate, a stable NO donor moiety. NO release was monitored with accurate parameters by real-time detection of gas and analysis of the accumulated release profile. Based on the NO release information, the selected safe level of NOP exhibited effective TM relaxation and a potential IOP lowering effect in vivo without side effects. This work provides new insights into nitric oxide release behavior that should be considered for glaucoma treatment

Nanoporous Block Copolymer Micelle/Micelle Multilayer Films with Dual Optical Properties

We introduce a novel and versatile approach for preparing self-assembled nanoporous multilayered films with tunable optical properties. Protonated polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) and anionic polystyrene-block-poly(acrylic acid) (PS-b-PAA) block copolymer micelles (BCM) were used as building blocks for the layer-by-layer assembly of BCM multilayer films. BCM film growth is governed by electrostatic and hydrogen-bonding interactions between the opposite BCMs. Both film porosity and film thickness are dependent upon the charge density of the micelles, with the porosity of the film controlled by the solution pH and the molecular weight (Mw) of the constituents. PS7K-b-P4VP28K/PS2K-b-PAA8K films prepared at pH 4 (for PS7K-b-P4VP28K) and pH 6 (for PS2K-b-PAA8K) are highly nanoporous and antireflective. In contrast, PS7K-b-P4VP28K/PS2K-b-PAA8K films assembled at pH 4/4 show a relatively dense surface morphology due to the decreased charge density of PS2K-b-PAA8K. Films formed from BCMs with increased PS block and decreased hydrophilic block (P4VP or PAA) size (e.g., PS36K-b-P4VP12K/PS16K-b-PAA4K at pH 4/4) were also nanoporous. This is attributed to a decrease in interdigitation between the adjacent corona shells of the low Mw BCMs, thus creating more void space between the micelles. Multilayer films with antireflective and photochromic properties were obtained by incorporating a water-insoluble photochromic dye (spiropyran) into the hydrophobic PS core of the BCMs assembled in the films. The optical properties of these films can be modulated by UV irradiation to selectively and reversibly control the transmission of light. Light transmission of higher than 99% was observed with accompanying photochromism in the (PS7K-b-P4VP28K/PS2K-b-PAA8K) multilayer films assembled at pH 4/6. Our approach highlights the potential to incorporate a range of materials, ranging from conventional hydrophilic materials with specific interactions to hydrophobic compounds, into the assembled BCMs to yield multifunctional nanoporous films

Enhanced Electrical Properties of Epoxy Resin with High Adhesion

In search of small dielectric constant (Dk) and low-dissipation (Df) energy substrates for high-frequency appliances, a benzoate-group-substituted bisphenol A based resin was synthesized from bisphenol A dibenzolate and bisphenol A diglycidyl ether. Compared to the common bisphenol A diglycidyl ether epoxy resin, introduction of the benzoate group was considered to lead to increased hydrophobic character, which was supported by water absorption investigation as well as absorption peak investigation of the OH region via Fourier transform infrared spectra. The cured resin with few water molecules exhibited restricted motion of the segment, and, consequently, thermally stable properties (coefficient of thermal expansion and thermogravimetric analysis) were achieved. Ultimately, the developed epoxy resin showed dramatically reduced Dk (3.05 at 1 GHz) and Df (0.016 at 1 GHz) values as well as enhanced adhesive properties. The excellent overall properties lead to its promising use in various fields involving electrical devices

Inherent Charge-Shifting Polyelectrolyte Multilayer Blends: A Facile Route for Tunable Protein Release from Surfaces

Recent research has highlighted degradable multilayer films that enable the programmed release of different therapeutics. Multilayers constructed by the layer-by-layer (LbL) deposition that can undergo disassembly have been demonstrated to be of considerable interest, particularly for biomedical surface coatings due to their versatility and mild aqueous processing conditions, enabling the inclusion of biologic drugs with high activity. In this study, we examine the controlled release of a protein using a different mechanism for film disassembly, the gradual dissociation of film interactions under release conditions. Poly(β-amino ester)s and poly(l-lysine) (PLL) were used as the positively charged multilayer components coassembled with a model negatively charged antigen protein, ovalbumin (Ova). The release of the protein from these multilayer films is dominated by the slow shift in the charge of components under physiological pH conditions rather than by hydrolytic degradative release. The time scale of release can be varied over almost 2 orders of magnitude by varying the ratio of the two polyamines in the deposition solution. The highly versatile and tunable properties of these films form a basis for designing controlled and sequential delivery of drug coatings using a variety of polyions

Facilitated Ion Transport in All-Solid-State Flexible Supercapacitors

The realization of highly flexible and all-solid-state energy-storage devices strongly depends on both the electrical properties and mechanical integrity of the constitutive materials and the controlled assembly of electrode and solid electrolyte. Herein we report the preparation of all-solid-state flexible supercapacitors (SCs) through the easy assembly of functionalized reduced graphene oxide (f-RGO) thin films (as electrode) and solvent-cast Nafion electrolyte membranes (as electrolyte and separator). In particular, the f-RGO-based SCs (f-RGO-SCs) showed a 2-fold higher specific capacitance (118.5 F/g at 1 A/g) and rate capability (90% retention at 30 A/g) compared to those of all-solid-state graphene SCs (62.3 F/g at 1A/g and 48% retention at 30 A/g). As proven by the 4-fold faster relaxation of the f-RGO-SCs than that of the RGO-SCs and more capacitive behavior of the former at the low-frequency region, these results were attributed to the facilitated ionic transport at the electrical double layer by means of the interfacial engineering of RGO by Nafion. Moreover, the superiority of all-solid-state flexible f-RGO-SCs was demonstrated by the good performance durability under the 1000 cycles of charging and discharging due to the mechanical integrity as a consequence of the interconnected networking structures. Therefore, this research provides new insight into the rational design and fabrication of all-solid-state flexible energy-storage devices as well as the fundamental understanding of ion and charge transport at the interface

Nitric Oxide Delivery Using Biocompatible Perfluorocarbon Microemulsion for Antibacterial Effect

Nitric oxide (NO) participates in various physiological and pathophysiological processes, for example, as a cell messenger and as an antimicrobial agent of the cell-mediated immune response. The development of NO-releasing materials to carry and deliver NO for biomedical applications has gained immense attention. NO-releasing perfluorooctane (PFO) microemulsion (ME) has been prepared using a simple and time-saving method. Perfluorocarbon (PFC) liquids are halogen-substituted carbon nonpolar oils with enhanced NO gas dissolution capacity. The solubility of NO in PFC liquids is higher than that in water-based fluids. Liquid–gas solubility is governed by Henry’s Law. The cytotoxicity of the NO-unloaded and NO-loaded PFO MEs toward human dermal fibroblast (HDF) was evaluated. The results showed that the NO-loaded PFO ME was highly biocompatible. On the other hand, at high concentrations the NO-releasing PFO ME accelerated the bacteria (Staphylococcus aureus) death unlike the NO-unloaded PFO ME. Hence, NO-releasing PFO MEs are suitable for biomedical applications such as wound healing and antibacterial agents