Unique Surfaces Research Articles

Structural, tribological, and mechanical properties of the hind leg joint of a jumping insect: Using katydids to inform bioinspired lubrication systems.

Relative to body length, insects can outjump most animals. They also accelerate their bodies at a much faster rate. Orthopterans (e.g., grasshoppers, crickets, and katydids) have hind legs that are specialized for jumping. Over an individual's lifetime, the hind leg joint endures repeated cycles of flexing and extending, including jumping, and its efficiency and durability easily surpass that of most mechanical devices. Although the efficient functioning of insect joints has long been recognized, the mechanism by which insect joints experience friction/adhesion/wear, and operate efficiently/reliably is still largely unknown. Our study on the structural, tribological, and mechanical properties of the orthopteran hind leg joints reveals the potential of katydid bioinspired research leading to more effective coatings and lubrication systems.

Nonmonotonic Self-Deformation of Cell Nuclei on Topological Surfaces with Micropillar Array.

Cells respond to the mechanical signals from their surroundings and integrate physiochemical signals to initiate intricate mechanochemical processes. While many studies indicate that topological features of biomaterials impact cellular behaviors profoundly, little research has focused on the nuclear response to a mechanical force generated by a topological surface. Here, we fabricated a polymeric micropillar array with an appropriate dimension to induce a severe self-deformation of cell nuclei and investigated how the nuclear shape changed over time. Intriguingly, the nuclei of mesenchymal stem cells (MSCs) on the poly(lactide-co-glycolide) (PLGA) micropillars exhibited a significant initial deformation followed by a partial recovery, which led to an "overshoot" phenomenon. The treatment of cytochalasin D suppressed the recovery of nuclei, which indicated the involvement of actin cytoskeleton in regulating the recovery at the second stage of nuclear deformation. Additionally, we found that MSCs exhibited different overshoot extents from their differentiated lineage, osteoblasts. These findings enrich the understanding of the role of the cell nucleus in mechanotransduction. As the first quantitative report on nonmonotonic kinetic process of self-deformation of a cell organelle on biomaterials with unique topological surfaces, this study sheds new insight into cell-biomaterial interactions.

Surface and Interface Engineering of Noble-Metal-Free Electrocatalysts for Efficient Energy Conversion Processes

Developing cost-effective and high-performance electrocatalysts for renewable energy conversion and storage is motivated by increasing concerns regarding global energy security and creating sustainable technologies dependent on inexpensive and abundant resources. Recent achievements in the design and synthesis of efficient non-precious-metal and even non-metal electrocatalysts make the replacement of noble metal counterparts for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) with earth-abundant elements, for example, C, N, Fe, Mn, and Co, a realistic possibility. It has been found that surface atomic engineering (e.g., heteroatom-doping) and interface atomic or molecular engineering (e.g., interfacial bonding) can induce novel physicochemical properties and strong synergistic effects for electrocatalysts, providing new and efficient strategies to greatly enhance the catalytic activities. In this Account, we discuss recent progress in the design and fabrication of efficient electrocatalysts based on carbon materials, graphitic carbon nitride, and transition metal oxides or hydroxides for efficient ORR, OER, and HER through surface and interfacial atomic and molecular engineering. Atomic and molecular engineering of carbon materials through heteroatom doping with one or more elements of noticeably different electronegativities can maximally tailor their electronic structures and induce a synergistic effect to increase electrochemical activity. Nonetheless, the electrocatalytic performance of chemically modified carbonaceous materials remains inferior to that of their metallic counterparts, which is mainly due to the relatively limited amount of electrocatalytic active sites induced by heteroatom doping. Accordingly, coupling carbon substrates with other active electrocatalysts to produce composite structures can impart novel physicochemical properties, thereby boosting the electroactivity even further. Although the majority of carbon-based materials remain uncompetitive with state-of-the-art metal-based catalysts for the aforementioned catalytic processes, non-metal carbon hybrids have already shown performance that typically only conventional noble metals or transition metal materials can achieve. The idea of hybridized carbon-based catalysts possessing unique active surfaces and macro- or nanostructures is addressed herein. For metal-carbon couples, the incorporation of carbon can effectively compensate for the intrinsic deficiency in conductivity of the metallic components. Chemical modification of carbon frameworks, such as nitrogen doping, not only can change the electron-donor character, but also can introduce anchoring sites for immobilizing active metallic centers to form metal-nitrogen-carbon (M-N-C) species, which are thought to facilitate the electrocatalytic process. With thoughtful material design, control over the porosity of composites, the molecular architecture of active metal moieties and macromorphologies of the whole catalysts can be achieved, leading to a better understanding structure-activity relationships. We hope that we can offer new insight into material design, particularly the role of chemical composition and structural properties in electrochemical performance and reaction mechanisms.

A unified mechanical and retention model for saturated and unsaturated soil behaviour

The coupled mechanical and water retention elasto-plastic constitutive model of Wheeler, Sharma and Buisson (the Glasgow coupled model, GCM) predicts unique unsaturated isotropic normal compression and unsaturated critical state planar surfaces for specific volume and degree of saturation when soil states are at the intersection of mechanical (M) and wetting retention (WR) yield surfaces. Experimental results from tests performed by Sivakumar on unsaturated samples of compacted speswhite kaolin confirm the existence and form of these unique surfaces. The GCM provides consistent representation of transitions between saturated and unsaturated conditions, including the influence of retention hysteresis and the effect of plastic volumetric strains on retention behaviour, and it gives unique expressions to predict saturation and de-saturation conditions (air-exclusion and air-entry points, respectively). Mechanical behaviour is modelled consistently across these transitions, including appropriate variation of mechanical yield stress under both saturated and unsaturated conditions. The expressions defining the unsaturated isotropic normal compression planar surfaces for specific volume and degree of saturation are central to the development of a relatively straightforward methodology for determining values of all GCM parameters (soil constants and initial state) from a limited number of laboratory tests. This methodology is demonstrated by application to the experimental data of Sivakumar. Comparison of model simulations with experimental results for the full set of Sivakumar’s isotropic loading stages demonstrates that the model is able to predict accurately the variation of both specific volume and degree of saturation during isotropic stress paths under saturated and unsaturated conditions.

In situ assembly of BiOI@Bi12O17Cl2p-n junction: charge induced unique front-lateral surfaces coupling heterostructure with high exposure of BiOI {001} active facets for robust and nonselective photocatalysis

Synthesis of reactive exposing facets and p-n junction are of great importance for semiconductor photocatalysis. Herein, we develop a p-n junction BiOI@Bi12O17Cl2 heterostructure via facilely in situ depositing BiOI nanosheets on the surface of Bi12O17Cl2 plates. Owing to the charge inducement, the BiOI nanosheets are all vertically assembled onto the Bi12O17Cl2 large plates to form a unique front-lateral surfaces coupling heterostructure, which enables high exposure of {001} reactive exposing facets of BiOI. The photocatalytic properties are systematically evaluated by degrading multiform industrial contaminants and antibiotic, like 2,4-dichlorophenol (2,4-DCP), rhodamine B (RhB), phenol, bisphenol A (BPA), and tetracycline hydrochloride. It reveals that the BiOI@Bi12O17Cl2 heterostructure not only shows dramatically strengthened photocatalytic activity, but also unfold powerful and nonselective photooxidation ability under visible-light illumination. The photoelectrochemical characterizations demonstrated that the drastically promoted separation and transfer of charge carriers that derived from the benefits of BiOI {001} active facets and BiOI@Bi12O17Cl2p-n junction are in charge of the high photo-activity. Detailed radicals detection and quantification experiments further corroborate our conclusions. The study may give us some new hints on designing novel heterostructured photoelectronic materials with integrating p-n junction and active exposing facets.

Obtaining a hyperelastic non-linear orthotropic material model via inverse bubble inflation analysis

An inverse bubble inflation test is proposed utilizing full displacement field matching to obtain non-linear material models suitable for the Finite Element (FE) method. In this paper a known non-linear orthotropic material model is assumed as the solution for the inverse method to illustrate the process. A bubble inflation FE analysis is performed with the known material model to determine the load and displacement field from the assumed material. Polynomial surfaces are fit to the nodal displacement values of the FE model, such that the entire displacement field is stored as three unique polynomial surfaces. An error formulation was established to quantify the quality of fit between different bubble inflation displacement fields. Gradient based optimization is used to obtain the assumed material model by matching the full displacement field. The inverse bubble inflation test successful produces a non-linear orthotropic model that is analogous to the assumed non-linear orthotropic material, and thus demonstrates that the inverse bubble inflation analysis would be able to characterize other non-linear orthotropic materials.

Interfacial characterization and electrocatalytic response of sonoelectrodeposited NiCo(OH)2 nanocomposites

In the present manuscript we describe the sonoelectrochemical synthesis of nanocomposites formed by nickel and cobalt hydroxide. The modified electrodes were characterized by electrochemical techniques such as Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). In order to study the electrocatalytic properties of the electrodes aiming the development of electrochemical sensors, glucose was employed as electrochemical probe. The nanocomposites electrode showed an excellent sensitivity and the kinetic parameters were evaluated by using Rotating Disk Electrode (RDE) measurements. Both RDE and EIS results indicated that the interfacial properties play the most important role on the electrocatalytic reaction where the surfaces of the modified electrodes were analyzed by using Scanning Electronic Microscopies (SEM). By this way, our findings contribute in the sensor technology on the achievement of unique nanostructured electrocatalytic surfaces, synthesized in a single step with the influence of the ultrasonic radiation.

Preparation of Thermoresponsive Nanostructured Surfaces for Tissue Engineering.

Thermoresponsive poly(N-isopropylacrylamide) (PIPAAm)-immobilized surfaces for controlling cell adhesion and detachment were fabricated by the Langmuir-Schaefer method. Amphiphilic block copolymers composed of polystyrene and PIPAAm (St-IPAAms) were synthesized by reversible addition-fragmentation chain transfer (RAFT) radical polymerization. A chloroform solution of St-IPAAm molecules was gently dropped into a Langmuir-trough apparatus, and both barriers of the apparatus were moved horizontally to compress the film to regulate its density. Then, the St-IPAAm Langmuir film was horizontally transferred onto a hydrophobically modified glass substrate by a surface-fixed device. Atomic force microscopy images clearly revealed nanoscale sea-island structures on the surface. The strength, rate, and quality of cell adhesion and detachment on the prepared surface were modulated by changes in temperature across the lower critical solution temperature range of PIPAAm molecules. In addition, a two-dimensional cell structure (cell sheet) was successfully recovered on the optimized surfaces. These unique PIPAAm surfaces may be useful for controlling the strength of cell adhesion and detachment.

Heterogeneous-surface-mediated crystallization control

The crystallization of matter at interfaces has long been a significant issue in science and technology, but surface-directed crystallization with controlled kinetics remains a matter of challenge. Here, we demonstrate a conceptual novel mechanism to steer liquid–solid phase transformation at interfaces by tailoring the chemical and structural inhomogeneity of a glass substrate through self-limited nanocrystallization of the glassy phase. Importantly, this approach enables large-scale development of metastable crystallization products, such as nanowire membranes. The thorough studies of the intermediate stages of crystallization reveal a unique cooperative mechanism in which the intricate interplays between inherent nanoscale forces and unique heterogeneous surfaces contribute to the mesoscale structural transformation from isolated units to superstructures. We further show that the constructed superstructures offer unprecedented opportuntities for the development of functional membrane systems possessing the combination of robust trace-detection performance and molecular trapping function. These findings not only present clear technological implications, but also provide an improved understanding of the fundamental mechanisms of surface-induced geological and biological processes. A glassy surface embedded with zones of crystalline order can spur materials to form nanowires and molecule-trapping membranes on demand. Surface-induced crystallization plays important roles in processes ranging from bone biomineralization to transistor fabrication. Shifeng Zhou from South China University of Technology in Guangzhou and co-workers have reported a great discovery that glass-ceramics surface can help to control liquid-to-solid transformations at interfaces without resorting to chemical treatments or specialized templates. Using thermal treatments, the team precipitated titanium dioxide nanocrystals into an otherwise homogenous inorganic oxide glass. The resulting non-uniform interface created periodic potential field that enabled strict control over crystal nucleation and aggregation. Additional charge imbalances between tiny aggregations guided materials to grow into remarkable superstructures. As a practical example, microporous silver membranes that detect trace amounts of hazardous aromatic vapours were demonstrated. A new surface-directed crystallization mechanism enabled by the chemical and structural inhomogeneity of the glass substrate through self-limited nanocrystallization of glassy phase was proposed and demonstrated. Benefiting from the intricate interplays between nanoscale force and heterogeneous surface, the strategy offers new opportunities in the large-scale development of various metastable crystallization products and also serves practical purpose.

Immobilization of Stimuli-Responsive Nanogels onto Honeycomb Porous Surfaces and Controlled Release of Proteins.

In this article, we describe the formation of functional honeycomb-like porous surfaces fabricated by the breath figures technique using blends of either amino-terminated poly(styrene) or a poly(styrene)-b-poly(acrylic acid) block copolymer with homopoly(styrene). Thus, the porous interfaces exhibited either amino or acid groups selectively located inside of the holes, which were subsequently employed to anchor stimuli-responsive nanogels by electrostatic interactions. These nanogels were prepared from poly(N-isopropylacrylamide) (PNIPAM) cross-linked with dendritic polyglycerol (dPG) and semi-interpenetrated with either 2-(dimethylamino)ethyl methacrylate (DMAEMA) or 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) to produce positively and negatively charged nanogel surfaces, respectively. The immobilization of these semi-interpenetrated networks onto the surfaces allowed us to have unique stimuli-responsive surfaces with both controlled topography and composition. More interestingly, the surfaces exhibited stimuli-responsive behavior by variations on the pH or temperature. Finally, the surfaces were evaluated regarding their capacity to induce a thermally triggered protein release at temperatures above the cloud point temperature (T(cp)) of the nanogels.

Understanding Surface Adhesion in Nature: A Peeling Model.

Nature often exhibits various interesting and unique adhesive surfaces. The attempt to understand the natural adhesion phenomena can continuously guide the design of artificial adhesive surfaces by proposing simplified models of surface adhesion. Among those models, a peeling model can often effectively reflect the adhesive property between two surfaces during their attachment and detachment processes. In the context, this review summarizes the recent advances about the peeling model in understanding unique adhesive properties on natural and artificial surfaces. It mainly includes four parts: a brief introduction to natural surface adhesion, the theoretical basis and progress of the peeling model, application of the peeling model, and finally, conclusions. It is believed that this review is helpful to various fields, such as surface engineering, biomedicine, microelectronics, and so on.

Influence of nanotopography on MC-3T3 cell adhesion and filopodia formation

Event Abstract Back to Event Influence of nanotopography on MC-3T3 cell adhesion and filopodia formation Dainelys Guadarrama Bello1, Aurélien Fouillen1, Antonella Badia2 and Antonio Nanci1 1 Universitéde Montréal, Laboratory for the Study of Calcified Tissues and Biomaterials, Department of Stomatology, Canada 2 Université de Montréal, Department of Chemistry, Canada Introduction: The interaction of cells with the surface of biomaterials determines the response of the host tissue and the ultimate success of an implant. Surface topography at all size scales is one of the key factors that influence the functional activity of cells in contact with biomaterials[1]. Our group has exploited simple chemical treatments to create unique nanoporous titanium surfaces that favor cell adhesion and formation of filopodia[2]. However, the influence of these filopodia on the adhesion strength remains unknown. Previous biomechanical studies by AFM faced some problems caused by irregularities on the titanium. In this study, we have tested the effect of chemical treatment time on generating a more planar nanoporous surface that will be amenable to the characterization of the composition, structure and adhesion of cell filopodia. Our ultimate aim is to better understand the biomechanical properties of filopodia and their contribution to adhesion strength and cell signaling. Materials and Methods: Commercially pure titanium discs (cp-Ti) were polished to a mirror finish. The polished discs were treated for various times ranging from 1 to 4 hours with a mixture of H2SO4 / H2O2 50/50 at room temperature to generate a nanoporous surface. Mouse calvaria-derived osteogenic cells (MC-3T3) were cultured in MEM-α and plated on polished (control) and nanoporous cp-Ti discs at a cell density of 10 000 cells/well. The cells were grown for periods up to 6h, 1 day and 3 days. Surface topography and cell morphology were examined using SEM and AFM. The actin network was visualised by florescence microscopy using rhodamin-phalloidin. Results and Discussion: SEM and AFM characterization showed that a 1.5 h treatment was adequate to produce a nanoporous surface with an overall planarity. SEM revealed that the cells developed more filopodia on this surface as compared with the control surface, confirming previous results with longer treatment times[3]. The filopodia displayed lateral protrusions known as nanopodia[4] that can contribute to the adhesive interaction of the filopodia with the surface. Figure 1. SEM micrograph of MC-3T3 grown for 6h on nanoporous titanium surface. Noteworthy, the reticulated nature of some cell projections on the nanoporous surface. Fluorescence microscopy also showed that the resulting nanoporous surface affects the organization of the actin network. Simple adjustment of the treatment time was therefore sufficient to achieve a mono planar nanoporous surface that allows cellular changes suggestive of increased osteogenic activity. Conclusions: We have shown that it is possible to create a planar nanoporous titanium surface that will be amenable to measuring the filopodia adhesion force. Such measurements will help to elucidate how nanoscale cell biomechanics induces and modulates cellular signalling so that surface topography can be used as an alternative to bioactive molecules. NSERC/CRSNG; RSBO; Université de Montréal

Carbon- and Nitrogen-Based Organic Frameworks.

This Account provides an overview of organic, covalent, porous frameworks and solid-state materials mainly composed of the elements carbon and nitrogen. The structures under consideration are rather diverse and cover a wide spectrum. This Account will summarize current works on the synthetic concepts leading toward those systems and cover the application side where emphasis is set on the exploration of those systems as candidates for unusual high-performance catalysis, electrocatalysis, electrochemical energy storage, and artificial photosynthesis. These issues are motivated by the new global energy cycles and the fact that sustainable technologies should not be based on rare and expensive resources. We therefore present the strategic design of functionality in cost-effective, affordable artificial materials starting from a spectrum of simple synthetic options to end up with carbon- and nitrogen-based porous frameworks. Following the synthetic strategies, we demonstrate how the electronic structure of polymeric frameworks can be tuned and how this can modify property profiles in a very unexpected fashion. Covalent triazine-based frameworks (CTFs), for instance, showed both enormously high energy and high power density in lithium and sodium battery systems. Other C,N-based organic frameworks, such as triazine-based graphitic carbon nitride, are suggested to show promising band gaps for many (photo)electrochemical reactions. Nitrogen-rich carbonaceous frameworks, which are developed from C,N-based organic framework strategies, are highlighted in order to address their promising electrocatalytic properties, such as in the hydrogen evolution reaction, oxygen reduction reaction (ORR), and oxygen evolution reaction (OER). With careful design, those materials can be multifunctional catalysts, such as a bifunctional ORR/OER electrocatalyst. Although the majority of new C,N-based materials are still not competitive with the best (usually nonsustainable candidates) for each application, the framework/N approach as such is still in its infancy and has already moved organic materials to regions where otherwise only traditional noble metals or special inorganic semiconductors are found. As one potential way to enhance the properties of polymeric frameworks, the idea of catalysts having unique active surfaces based on Mott-Schottky heterojunctions and related concepts are addressed. In order to integrate all of the above versatile subjects from synthesis to applications on C,N-based organic frameworks, we begin the discussion with synthetic concepts and strategies for these frameworks to distinguish these systems from typical covalent organic frameworks based on boron oxide rings. Next we focus on the semiconducting properties of C,N-based organic frameworks in order to show a continuous transition between CTFs and other systems, such as graphitic carbon nitrides. At the end, applications of these materials are shown by highlighting their properties in electrochemical energy storage and photo- and electrocatalysis.

Grain-boundary-dependent CO2 electroreduction activity.

Uncovering new structure-activity relationships for metal nanoparticle (NP) electrocatalysts is crucial for advancing many energy conversion technologies. Grain boundaries (GBs) could be used to stabilize unique active surfaces, but a quantitative correlation between GBs and catalytic activity has not been established. Here we use vapor deposition to prepare Au NPs on carbon nanotubes (Au/CNT). As deposited, the Au NPs have a relatively high density of GBs that are readily imaged by transmission electron microscopy (TEM); thermal annealing lowers the density in a controlled manner. We show that the surface-area-normalized activity for CO2 reduction is linearly correlated with GB surface density on Au/CNT, demonstrating that GB engineering is a powerful approach to improving the catalytic activity of metal NPs.

Shape-controlled synthesis of Fe3O4/CeO2hybrid octahedra for lipase immobilization

Fe3O4/CeO2 hybrid octahedra have been successfully synthesized on the large scale via a solvothermal route, which were confirmed by a series of modern analytical tools. The formation and evolution of Fe3O4/CeO2 hybrid octahedra were systematically investigated, and a kinetically induced anisotropic growth mechanism clearly contributes to the formation of the novel architecture. Because of the magnetic nature and unique surfaces, the as-prepared Fe3O4/CeO2 hybrid octahedra were employed as magnetic carriers for lipase immobilization. Our results indicated that the lipase loading amount on the magnetic Fe3O4/CeO2 nanoparticles was about 43.1 mg of protein per g. Hydrolytic activity tests revealed that the immobilized lipase retains about 92.4% of the free enzyme's activity. The reusability assay revealed that the immobilized lipase can be reused 3 times without marked loss of catalytic activity (<5%). Most importantly, the thermal, acid and alkali stabilities of immobilized lipase were strikingly improved. It is hoped that the Fe3O4/CeO2 hybrid octahedra may find applications in biotechnology and biocatalysis.

Laser-Machined Microchannel Effect on Microstructure and Oxide Formation of an Ultrasonically Processed Aluminum Alloy

Ultrasonic consolidation (UC) has been proven to be a suitable method for fiber embedment into metal matrices. To aid successful embedment of high fiber volumes and to ensure their accurate positioning, research on producing microchannels in combination with adjacent shoulders formed by distribution of the melt onto unique UC sample surfaces with a fiber laser was carried out. This paper investigated the effect of the laser on the microstructure surrounding the channel within an Al 3003-H18 sample. The heat input and the extent of the heat-affected zone (HAZ) from one and multiple passes was examined. The paper explored the influence of air, as an assist gas, on the shoulders and possible oxide formation with regards to future bonding requirements during UC. The authors found that one laser pass resulted in a keyhole-shaped channel filled with a mixture of aluminum and oxides and a symmetrical HAZ surrounding the channel. Multiple passes resulted in the desired channel shape and a wide HAZ which appeared to be an eutectic microstructure. The distribution of molten material showed oxide formation all along the channel outline and especially within the shoulder.

Robust Laser Speckle Authentication System through Data Mining Techniques

This paper proposes a speckle image recognition method using data mining techniques to ensure speckle identification system feasible for authentication. This is an interdisciplinary method that integrates the researches of optics, data mining, and image processing. Because objects have unique but imperfect surfaces, their laser speckle is capable of providing suitable identifiable features for authentication. In our method, matching points among speckle images acquired from one plastic card are extracted by scale-invariant feature transform (SIFT). The spatial relations among the matching points are then transformed to 9 direction lower triangular (9DLT) representations. Then, the Apriori algorithm mines frequent patterns so a useful association rule is obtained as the feature to identify the similarity between each of the speckle images for the purpose of authenticity verification. The proposed method is especially robust in the cases of card displacement and luminance change resulted from laser attenuation. Experimental results show that the proposed method has promising results and outperforms existing methods in identification accuracy.

Generation of Electrochemical Gradient from Peptide Self-Assembly

The nucleating core of the Amyloid β peptide associated with Alzheimer's disease is able to organize into a peptide bilayer maintaining dimensions similar to biological phospholipid membranes. However, the dynamics of the hydrogen-bonded peptides are certainly different from the flexible alkanes of the lipid membranes, and this crystallinity prompted us to consider their dynamics and functional potential. Here we will review these unique surfaces built on cross-β structures of amyloid, and extend that pattern to mixing of positively- and negatively-charged surfaces to give even higher order architectures with high electrochemical potential across the 4 nm membrane. Further, we have developed EFM analyses to map the charge distribution and explored novel energy or electron transduction reactions. Our results show that these peptide membrane scaffolds are dynamic, and their ability to self-organize offers a new opportunity for engineering specific molecular recognition elements into the peptide assemblies and well-ordered materials.

The otologist's tuning fork examination--are you striking it correctly?

To determine if the manner in which a tuning fork is activated affects its vibrational response. Diagnostic test assessment. Hearing Center of Excellence laboratory. A Polytec OFV-5000 scanning vibrometer was used to measure the vibrational response of 256-Hz, 512-Hz, and 1024-Hz tuning forks after activation. The tuning forks were activated to varying intensities by striking 4 unique surfaces: the head, palm, a metal surface, and a wood table. The fundamental frequency of the individual tuning fork was the dominant observed frequency in all testing scenarios. Additional nonharmonic frequencies were noted when the 256-Hz and 512-Hz tuning forks were struck off metal and wooden surfaces. Additional nonfundamental sound frequencies produced secondary to striking a tuning fork off a metal object or a wooden table could affect clinical tuning fork examination and complicate decisions regarding surgical candidacy.

Thermoresponsive nanostructured surfaces generated by the Langmuir-Schaefer method are suitable for cell sheet fabrication.

Thermoresponsive poly(N-isopropylacrylamide) (PIPAAm)-immobilized surfaces for controlling cell adhesion and detachment were fabricated by the Langmuir-Schaefer method. Block copolymers composed of polystyrene and PIPAAm (St-IPAAms) having various chain lengths and compositions were synthesized by reversible addition-fragmentation chain transfer radical polymerization. The St-IPAAm Langmuir film at an air-water interface was horizontally transferred onto a hydrophobically modified glass substrate while regulating its density. Atomic force microscopy images clearly visualized nanoscaled sea-island structures on the surface. By adjusting both the composition of St-IPAAms and the density of immobilized PIPAAms, a series of thermoresponsive surfaces was prepared to control the strength, rate, and quality of cell adhesion and detachment through changes in temperature across the lower critical solution temperature range of PIPAAm molecules. In addition, a two-dimensional cell structure (cell sheet) was more rapidly recovered on the optimized surfaces than on conventional PIPAAm surfaces. These unique PIPAAm surfaces are suggested to be useful for controlling the strength of cell adhesion and detachment.