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Nature May 2016Two-dimensional (2D) crystalline materials possess unique structural, mechanical and electronic properties that make them highly attractive in many applications....
Two-dimensional (2D) crystalline materials possess unique structural, mechanical and electronic properties that make them highly attractive in many applications. Although there have been advances in preparing 2D materials that consist of one or a few atomic or molecular layers, bottom-up assembly of 2D crystalline materials remains a challenge and an active area of development. More challenging is the design of dynamic 2D lattices that can undergo large-scale motions without loss of crystallinity. Dynamic behaviour in porous three-dimensional (3D) crystalline solids has been exploited for stimuli-responsive functions and adaptive behaviour. As in such 3D materials, integrating flexibility and adaptiveness into crystalline 2D lattices would greatly broaden the functional scope of 2D materials. Here we report the self-assembly of unsupported, 2D protein lattices with precise spatial arrangements and patterns using a readily accessible design strategy. Three single- or double-point mutants of the C4-symmetric protein RhuA were designed to assemble via different modes of intermolecular interactions (single-disulfide, double-disulfide and metal-coordination) into crystalline 2D arrays. Owing to the flexibility of the single-disulfide interactions, the lattices of one of the variants ((C98)RhuA) are essentially defect-free and undergo substantial, but fully correlated, changes in molecular arrangement, yielding coherently dynamic 2D molecular lattices. (C98)RhuA lattices display a Poisson's ratio of -1-the lowest thermodynamically possible value for an isotropic material-making them auxetic.
Topics: Aldehyde-Lyases; Crystallization; Disulfides; Escherichia coli; Metals; Microscopy, Electron, Transmission; Models, Molecular; Mutant Proteins; Pliability; Protein Conformation; Rotation; Stress, Mechanical; Thermodynamics
PubMed: 27135928
DOI: 10.1038/nature17633 -
Dental Materials : Official Publication... Mar 2016This study evaluated the effect of addition of alumina particles (polycrystalline or monocrystalline), with or without silica coating, on the optical and mechanical...
OBJECTIVES
This study evaluated the effect of addition of alumina particles (polycrystalline or monocrystalline), with or without silica coating, on the optical and mechanical properties of a porcelain.
METHODS
Groups tested were: control (C), polycrystalline alumina (PA), polycrystalline alumina-silica (PAS), monocrystalline alumina (MA), monocrystalline alumina-silica (MAS). Polycrystalline alumina powder was synthesized using a polymeric precursor method; a commercially available monocrystalline alumina powder (sapphire) was acquired. Silica coating was obtained by immersing alumina powders in a tetraethylorthosilicate solution, followed by heat-treatment. Electrostatic stable suspension method was used to ensure homogenous dispersion of the alumina particles within the porcelain powder. The ceramic specimens were obtained by heat-pressing. Microstructure, translucency parameter, contrast ratio, opalescence index, porosity, biaxial flexural strength, roughness, and elastic constants were characterized.
RESULTS
A better interaction between glass matrix and silica coated crystalline particles is suggested in some analyses, yet further investigation is needed to confirm it. The materials did not present significant differences in biaxial flexural strength, due to the presence of higher porosity in the groups with alumina addition. Elastic modulus was higher for MA and MAS groups. Also, these were the groups with optical qualities and roughness closer to control. The PA and PAS groups were considerably more opaque as well as rougher.
SIGNIFICANCE
Porcelains with addition of monocrystalline particles presented superior esthetic qualities compared to those with polycrystalline particles. In order to eliminate the porosity in the ceramic materials investigated herein, processing parameters need to be optimized as well as different glass frites should be tested.
Topics: Aluminum Oxide; Ceramics; Coated Materials, Biocompatible; Crystallization; Dental Porcelain; Dental Stress Analysis; Hot Temperature; Materials Testing; Particle Size; Pliability; Porosity; Surface Properties
PubMed: 26754431
DOI: 10.1016/j.dental.2015.12.009 -
Scientific Reports Nov 2020The efforts to improve the treatment efficacy in blind patients with retinal degenerative diseases would greatly benefit from retinal activity feedback, which is lacking... (Comparative Study)
Comparative Study
The efforts to improve the treatment efficacy in blind patients with retinal degenerative diseases would greatly benefit from retinal activity feedback, which is lacking in current retinal implants. While the door for a bidirectional communication device that stimulates and records intraretinally has been opened by the recent use of silicon-based penetrating probes, the biological impact induced by the insertion of such rigid devices is still unknown. Here, we developed for the first time, flexible intraretinal probes and validated in vitro the acute biological insertion impact in mouse retinae compared to standard silicon-based probes. Our results show that probes based on flexible materials, such as polyimide and parylene-C, in combination with a narrow shank design 50 µm wide and 7 µm thick, and the use of insertion speeds as high as 187.5 µm/s will successfully penetrate the retina, reduce the footprint of the insertion to roughly 2 times the cross-section of the probe, and induce low dead cell counts, while keeping the vitality of the tissue and recording the neural activity at different depths.
Topics: Animals; Electrodes, Implanted; Equipment Design; Feedback, Physiological; Materials Testing; Mice; Microelectrodes; Phantoms, Imaging; Pliability; Retina; Silicon
PubMed: 33199768
DOI: 10.1038/s41598-020-76582-5 -
Nano Letters Jun 2019The unique structure and mechanical properties of syringe-injectable mesh electronics have enabled seamless tissue integration and stable chronic recording of the...
The unique structure and mechanical properties of syringe-injectable mesh electronics have enabled seamless tissue integration and stable chronic recording of the activities of the same neurons on a year scale. Here, we report studies of a series of structural and mechanical mesh electronics design variations that allow injection using needles at least 4-fold smaller than those previously reported to minimize the footprint during injection of the electronics in soft matter and tissue. Characterization of new ultraflexible two-dimensional (2D) and one-dimensional (1D) probes has demonstrated reproducible injection of the newly developed mesh electronics designs via needles as small as 100 μm in inner diameter (ID) with reduced injection volumes. In vitro hydrogel and in vivo mouse brain studies have shown that ultraflexible 2D and 1D probes maintain their structural integrity and conformation post-injection after being transferred through the reduced diameter needles. In addition, analysis of the variation of the post-injection mesh cross sections suggests a smaller degree of tissue deformation and relaxation with decreasing needle diameters. The capability to implement rational design for mesh electronic probes that can be delivered via much smaller diameter needles should open up new opportunities for integration of electronics with tissue and soft matter in fundamental and translational studies.
Topics: Animals; Biomimetic Materials; Brain; Electronics, Medical; Equipment Design; Injections; Mice; Needles; Neurons; Pliability; Prostheses and Implants
PubMed: 31075202
DOI: 10.1021/acs.nanolett.9b01727 -
Biochemistry Jul 2018Electrophysiology tools have contributed substantially to understanding brain function, yet the capabilities of conventional electrophysiology probes have remained...
Electrophysiology tools have contributed substantially to understanding brain function, yet the capabilities of conventional electrophysiology probes have remained limited in key ways because of large structural and mechanical mismatches with respect to neural tissue. In this Perspective, we discuss how the general goal of probe design in biochemistry, that the probe or label have a minimal impact on the properties and function of the system being studied, can be realized by minimizing structural, mechanical, and topological differences between neural probes and brain tissue, thus leading to a new paradigm of tissue-like mesh electronics. The unique properties and capabilities of the tissue-like mesh electronics as well as future opportunities are summarized. First, we discuss the design of an ultraflexible and open mesh structure of electronics that is tissue-like and can be delivered in the brain via minimally invasive syringe injection like molecular and macromolecular pharmaceuticals. Second, we describe the unprecedented tissue healing without chronic immune response that leads to seamless three-dimensional integration with a natural distribution of neurons and other key cells through these tissue-like probes. These unique characteristics lead to unmatched stable long-term, multiplexed mapping and modulation of neural circuits at the single-neuron level on a year time scale. Last, we offer insights on several exciting future directions for the tissue-like electronics paradigm that capitalize on their unique properties to explore biochemical interactions and signaling in a "natural" brain environment.
Topics: Action Potentials; Animals; Biomimetic Materials; Brain; Electrodes, Implanted; Electronics; Electrophysiological Phenomena; Equipment Design; Humans; Nerve Net; Neurons; Pliability; Single-Cell Analysis
PubMed: 29529359
DOI: 10.1021/acs.biochem.8b00122 -
Nano Letters Aug 2019Polymer-based electronics with low bending stiffnesses and high flexibility, including recently reported macroporous syringe-injectable mesh electronics, have shown...
Polymer-based electronics with low bending stiffnesses and high flexibility, including recently reported macroporous syringe-injectable mesh electronics, have shown substantial promise for chronic studies of neural circuitry in the brains of live animals. A central challenge for exploiting these highly flexible materials for in vivo studies has centered on the development of efficient input/output (I/O) connections to an external interface with high yield, low bonding resistance, and long-term stability. Here we report a new paradigm applied to the challenging case of injectable mesh electronics that exploits the high flexibility of nanoscale thickness two-sided metal I/O pads that can deform and contact standard interface cables in high yield with long-term electrical stability. First, we describe the design and facile fabrication of two-sided metal I/O pads that allow for contact without regard to probe orientation. Second, systematic studies of the contact resistance as a function of I/O pad design and mechanical properties demonstrate the key role of the I/O pad bending stiffness in achieving low-resistance stable contacts. Additionally, computational studies provide design rules for achieving high-yield multiplexed contact interfacing in the case of angular misalignment such that adjacent channels are not shorted. Third, the in vitro measurement of 32-channel mesh electronics probes bonded to interface cables using the direct contact method shows a reproducibly high yield of electrical connectivity. Finally, in vivo experiments with 32-channel mesh electronics probes implanted in live mice demonstrate the chronic stability of the direct contact interface, enabling consistent tracking of single-unit neural activity over at least 2 months without a loss of channel recording. The direct contact interfacing methodology paves the way for scalable long-term connections of multiplexed mesh electronics neural probes for neural recording and modulation and moreover could be used to facilitate a scalable interconnection of other flexible electronics in biological studies and therapeutic applications.
Topics: Animals; Electrodes, Implanted; Electronics, Medical; Equipment Design; Injections; Mice; Pliability; Syringes
PubMed: 31361503
DOI: 10.1021/acs.nanolett.9b03019 -
Journal of Neural Engineering Jun 2019Implanted microelectrodes provide a unique means to directly interface with the nervous system but have been limited by the lack of stable functionality. There is...
OBJECTIVE
Implanted microelectrodes provide a unique means to directly interface with the nervous system but have been limited by the lack of stable functionality. There is growing evidence suggesting that substantially reducing the mechanical rigidity of neural electrodes promotes tissue compatibility and improves their recording stability in both the short- and long-term. However, the miniaturized dimensions and ultraflexibility desired for mitigating tissue responses preclude the probe's self-supported penetration into the brain tissue.
APPROACH
Here we demonstrate the high-throughput implantation of multi-shank ultraflexible neural electrode arrays with surgical footprints as small as 200 µm in a mouse model. This is achieved by using arrays of tungsten microwires as shuttle devices, and bio-dissolvable adhesive polyethylene glycol (PEG) to temporarily attach a shank onto each microwire.
MAIN RESULTS
We show the ability to simultaneously deliver electrode arrays in designed patterns, to adjust the implantation locations of the shanks by need, to target different brain structures, and to control the surgical injury by reducing the microwire diameters to cellular scale.
SIGNIFICANCE
These results provide a facile implantation method to apply ultraflexible neural probes in scalable neural recording.
Topics: Animals; Brain; Electrodes, Implanted; Male; Mice; Mice, Inbred C57BL; Microelectrodes; Minimally Invasive Surgical Procedures; Neurons; Pliability; Stereotaxic Techniques
PubMed: 30736013
DOI: 10.1088/1741-2552/ab05b6 -
The Angle Orthodontist 1997The materials used by orthodontists have changed rapidly in recent years and will continue to do so in the future. As esthetic composite archwires are introduced,... (Review)
Review
The materials used by orthodontists have changed rapidly in recent years and will continue to do so in the future. As esthetic composite archwires are introduced, metallic archwires will likely be replaced for most orthodontic applications in the same way that metals have been replaced by composites in the aerospace industry. Archwires are reviewed in the order of their development, with emphasis on specific properties and characteristics, such as strength, stiffness, range, formability, and weldability. Because an ideal material has not yet been found, archwires should be selected within the context of their intended use during treatment.
Topics: Chemical Phenomena; Chemistry, Physical; Composite Resins; Dental Alloys; Dental Soldering; Esthetics, Dental; Forecasting; Humans; Orthodontic Appliance Design; Orthodontic Wires; Pliability; Stress, Mechanical
PubMed: 9188964
DOI: 10.1043/0003-3219(1997)067<0197:AROCAT>2.3.CO;2 -
Dental Materials Journal Mar 2019The aim was to evaluate the effect of different zirconia discontinuous fiber fractions on radiopacity and other selected properties of glass discontinuous...
The aim was to evaluate the effect of different zirconia discontinuous fiber fractions on radiopacity and other selected properties of glass discontinuous fiber-reinforced flowable composite (Exp-SFRC). Exp-SFRC was prepared by mixing 30 wt% of resin-matrix and 45 wt% of particulate-fillers to 25 wt% of various weight-fractions of E-glass/zirconia discontinuous fiber-fillers (25:0, 20:5, 15:10, 10:15, 0:25 wt%). Flexural strength and fracture toughness were determined for each experimental material. Radiograph of each Exp-SFRC and aluminium step wedge were taken to determine the radiopacity. Degree of conversion and light-transmission were also measured. Scanning electron microscopy was used to evaluate the microstructure of the Exp-SFRC. Analysis of variance (ANOVA) revealed that fractions of E-glass/zirconia discontinuous fiber-fillers had significant effect (p<0.05) on radiopacity and other tested properties of the Exp-SFRCs. Replacing low fraction of E-glass fiber with zirconia fiber-fillers can increase the radiopacity of the fiber-reinforced composite without deteriorating the mechanical properties, although, degree of conversion was decreased.
Topics: Composite Resins; Glass; Materials Testing; Pliability; Stress, Mechanical; Surface Properties
PubMed: 30449830
DOI: 10.4012/dmj.2018-102 -
Sensors (Basel, Switzerland) Feb 2020Wearable health-monitoring systems should be comfortable, non-stigmatizing, and able to achieve high data quality. Smart textiles with electronic elements integrated...
Wearable health-monitoring systems should be comfortable, non-stigmatizing, and able to achieve high data quality. Smart textiles with electronic elements integrated directly into fabrics offer a way to embed sensors into clothing seamlessly to serve these purposes. In this work, we demonstrate the feasibility of electrocardiogram (ECG) monitoring with sewn textile electrodes instead of traditional gel electrodes in a 3-lead, chest-mounted configuration. The textile electrodes are sewn with silver-coated thread in an overlapping zig zag pattern into an inextensible fabric. Sensor validation included ECG monitoring and comfort surveys with human subjects, stretch testing, and wash cycling. The electrodes were tested with the BIOPAC MP160 ECG data acquisition module. Sensors were placed on 8 subjects (5 males and 3 females) with double-sided tape. To detect differences in R peak detectability between traditional and sewn sensors, effect size was set at 10% of a sample mean for heart rate (HR) and R-R interval. Paired student's t-tests were run between adhesive and sewn electrode data for R-R interval and average HR, and a Wilcoxon signed-rank test was run for comfort. No statistically significant difference was found between the traditional and textile electrodes (R-R interval: t = 1.43, > 0.1; HR: t = - 0.70, > 0.5; comfort: V = 15, > 0.5).
Topics: Adhesiveness; Electric Impedance; Electrocardiography; Electrodes; Female; Heart Rate; Humans; Male; Pliability; Textiles; Wearable Electronic Devices
PubMed: 32069937
DOI: 10.3390/s20041013