Acetate Sheets Research Articles

Hydrogen Boride Sheets and Copper Nanoparticle Composites as a Visible‐Light‐Sensitive Hydrogen Release System

AbstractHydrogen boride (HB) sheet is a new class of 2D materials comprising hydrogen and boron, synthesized through ion‐exchange and exfoliation techniques. HB sheets can release hydrogen (H2) under light irradiation and is predicted to be a promising H2 storage material. However, its application is limited to the UV region. One approach to enable a visible‐light‐driven system is the utilization of plasmonic metallic nanoparticles. The present study reports H2 release from copper (Cu) nanoparticle‐modified HB sheet (HB/Cu) under visible‐light irradiation. Copper nanoparticles possess unique and strong plasmonic responses in the visible‐light range, making them ideal light absorbers in this system. HB/Cu nanocomposites are synthesized using a simple mixture of copper acetate and HB sheets in acetonitrile, where HB sheets reduced copper ions to metal copper nanoparticles. The photoirradiation results shows that HB/Cu nanocomposites released more H2 than the bare HB sheets under visible‐light irradiation. This is probably due to the plasmonic photothermal effect of copper metal, which enhances H2 generation from the HB sheets. This material offers a viable and cost‐effective approach for developing visible‐light‐sensitive systems.

Cellulose acetate sheet supported gold nanoparticles for the catalytic reduction of toxic organic pollutants

Abstract Water contamination by toxic organic dyes represents a significant global challenge necessitating effective remediation strategies. Due to their high catalytic activity, considerable attention has been gained to metal-based nanocatalysts. Cellulose acetate sheets supported by gold nanoparticles through a reduction method were synthesized. The composite synthesized material presents a compelling platform for catalytic reduction in the remediation of toxic organic pollutants, ensuring controlled particle size and stability. In this study, the prepared cellulose acetate sheet (CAsheet) was dipped in a 0.001 M aqueous chloroauric acid (HAuCl4) solution and reduced by immersion in a 0.1 M sodium borohydride (NaBH4) aqueous solution. After the successful preparation of virgin cellulose acetate sheet (CAsheet) and gold-supported cellulose acetate sheet (Au-CAsheet) samples were assessed by scanning electron microscopy (SEM), X-ray crystallography (XRD), energy dispersive X-rays spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR) analysis. The catalytic reduction reaction of toxic compounds i.e. reduction of 4-nitroaniline (4-NA), Congo red (CR), and reactive yellow (RY-42) by using NaBH4. The catalytic activity of the Au-CAsheet was exhibited by the reaction rate constant (k app) values 0.3189, 0.1596, and 0.1593 min−1 for CR, 4-NA, and RY-42 respectively. This kind of procedure for Au-CAsheet synthesis may be valid for different applications in catalysis, sensing, and environmental application.

Oleic acid decorated kraft lignin as a hydrophobic and functional filler of cellulose acetate films

The packaging industry has primarily been dominated by single-use, petrochemical-sourced plastic materials despite their short-term use. Their leakage into the ecosystem after their use poses substantial environmental concerns. As a result, compostable and renewable packaging material alternatives are garnering significant attention. Cellulose acetate is a derivative of cellulose that exhibits excellent tensile properties, transparency, melt processability, and intermediate compostability. However, its application in the food packaging industry is limited due to its hygroscopic behavior and lack of dimensional stability. This study investigated using lignin (pristine and esterified) as a functional additive of cellulose acetate. The effect of varying concentrations of pristine kraft and oleic acid functionalized lignin in the cellulose acetate matrix and its effect on the resulting film's mechanical, morphological, viscoelastic, and water barrier properties were explored. Comprehensive characterization of the thermomechanical processed lignin-cellulose acetate sheets revealed reduced moisture absorption, improved UV and moisture barrier, and enhanced tensile properties with melt processability. Overall, the studied films could have appealing properties for food and other packaging applications, thus, serving as eco-friendly and sustainable alternatives to conventional petroleum-derived packing materials.

Clinical and microbiological predictors of healing in Buruli ulcer disease

IntroductionWound measurements are relevant in monitoring the rate of healing (RoH) and may predict time to healing. Predicting the time to healing can help improve the management of Buruli ulcer. We examine three methods for the determination of RoH and their use as predictors of time to healing. MethodsLesion measurements of Buruli ulcer patients treated from 2007 to 2022 were obtained with acetate sheet tracings (2D) or Aranz software (3D) fortnightly. RoH was determined using the absolute area, percentage area reduction and linear methods at 4 weeks post onset of antibiotic treatment. Predicted time to healing was compared to the actual healing time. Baseline characteristics were assessed for associations with healing. ResultsAll three methods for calculating the RoH significantly distinguished between fast and slow healers (p < 0.0001). The predicted healing time using the linear method was comparable to the actual healing time for fast healers (p = 0.34). The RoH was influenced by the form of lesion, with plaques [OR 2.19 5 %CI (1.2–3.6), p = 0.009], and oedemas [OR 8.5; 95 %CI (1.9––36.9), p = 0.004] being associated with delayed healing. The proportion of patients with paradoxical reactions 16 % vs 3 %, p < 0.0001), higher baseline bacterial load (75/104;72 % vs 21/47;45 %, p = 0.001) and delayed clearance of viable organisms (71/104;68 % vs 9/47;19 %, p < 0.0001) was higher in the slow healers than the fast healers. ConclusionPredicted healing rates were comparatively lower for slow healers than fast healers. Baseline characteristics associated with healing can be explored for an improved disease management plan to reduce patient and caregiver anxiety.

A Simple and Fast Compression‐Based Method to Fabricate Responsive Gold‐pNIPAM Hybrid Materials: From Thin Films to Anisotropic Microgels

AbstractIn recent years, hydrogel‐based soft materials with hybrid properties have found widespread use in various technological fields, including tissue engineering, soft actuators, and flexible electronics. The proper implementation of these smart multifunctional materials into real‐world applications requires the development of simple, cost‐effective, and large‐scale fabrication methods. Herein, a simple compression‐ and colloid‐based method is presented to fabricate responsive Au‐poly(N‐isopropylacrylamide) (pNIPAM) hybrid films using photopolymerizable resin containing Au‐pNIPAM core–shell microgels as building blocks. Uniform Au‐pNIPAM hybrid films of 25 × 25 mm with adjustable thickness in the micron‐size range (2.3–1.2 µm) w ere successfully fabricated on glass substrates and flexible commercial acetate sheets. The resulting flexible Au‐pNIPAM films exhibit robust optical and mechanical properties, even after repeated edge‐to‐edge bending cycle tests. Additionally, using patterned light to polymerize the Au‐pNIPAM films allows synthesizing of anisotropic Au‐pNIPAM microgels with high width‐to‐height aspect ratios, such as square, circular, and rectangular microgels, adding a new dimension to the proposed fabrication method.

Preparation and Use of Low-Cost Electrochemical Sensors

Since the decade of the 90s when the first works of professor Joseph Wang were published, screen-printed electrodes have been proposed for many objectives. In the first works in Brazil a few years later, some authors proposed electrochemical sensors using graphite from batteries, which provide great results for the determination of several analytes.1 In another interesting work, Professor Lucio Angnes (USP) and collaborators prepared gold electrodes from CD, which presented a thin film of the noble metal.2 They obtained an extremely low-cost electrochemical sensor. After that, this research line gained notoriety in Brazil, and the number of groups and papers has increased considerably. In this regard, we can highlight some researchers that have been working on low-cost and disposable electrochemical sensors, including Lauro Kubota (UNICAMP), Luiz Humberto Marcolino Junior (UFPR), Márcio Fernando Bergamini (UFPR), Ronaldo Censi Faria (UFSCar), Éder Cavalheiro (USP), Osvaldo Novais de Oliveira Junior (USP), Sergio Spínola (USP), Murilo Santiago (CNPEM), Renato Souza Lima (CNPEM), Orlando Fatibello Filho (UFSCar), Wendell Coltro (USP), William Reis (UNICAMP), and Thiago Paixão (USP). The laboratory of Sensors, Nanomedicine, and Nanostructured Materials (LSNano) located at UFSCar Araras has also developed low-cost sensors using recyclable materials and conductive inks with simple preparation. Low-cost electrodes can be prepared with infinite possibilities by using different substrates, such as circuit boards,3 acetate sheets,4 and polyethylene terephthalate (PET) from bottles5 as well as paper6. In the last example, various types of papers have been applied in this area, including cardboard,7 waterproof,6 and adhesives8. Therefore, materials that we use daily can become important devices with great applications. There are many options to produce low-cost electrochemical sensors, including pencil drawing, stencil, laser scribing, and screen-printing techniques.9 The strategy depends on the subject and the materials that have been deposited to be used as conductors. In this context, the screen-printing technique is come from the t-shirt preparation and is an excellent alternative to produce hundreds of sensors in a few minutes. They can be applied by using different electrochemical techniques, such as potentiometry, voltammetry, and electrochemical impedance spectroscopy. For this purpose, low-cost inks, which are made of a polymer and a conductive material, are necessary. Conductive inks can be prepared with water based-polymers,10 nail polish,11 and traditional polymers based on organic solvents12. Otherwise, graphite carbon nanotubes and/or graphene and carbon dots have been used as conductive carbon-based materials.13 Also, metallic nanoparticles such as copper, platinum, and gold can be great alternatives for this intention but can be quite costly.

Clinical evaluation of the remineralizing effect of a mouthguard and paste containing S-PRG filler on white spot lesions

White spot lesions (WSLs) are frequently observed on young permanent teeth. The aim of this clinical study was to evaluate the remineralizing effect of paste and a mouthguard containing surface pre-reacted glass-ionomer (S-PRG) filler by observing and measuring lesion area. A total of 14 children (age range, 8–16 years) with WSLs involving 74 teeth attending Asahi University Medical & Dental Center were examined. Color- and size-matching stickers (Cas Match™, Bear Medic) were photographed with involved teeth. Mouthguards made of an S-PRG filler-containing ethylene-vinyl acetate sheet (sample; SHOFU) with S-PRG filler-containing paste (PRG Pro-Care Gel®; SHOFU) (PRG MG-Paste group) or without paste (PRG MG group; control) were applied to WSLs at bedtime. No teeth required restoration due to caries progression during the experimental period. Mean reductions in lesion area at 6 months after treatment in the PRG MG-Paste group and PRG MG group were 1.66 ± 1.84 mm2 and 0.81 ± 1.27 mm2, respectively. Significant differences were observed between groups (p < 0.05). No significant difference in area reduction was seen between kinds of teeth involved, although significant differences in area reduction were observed among individual subjects. These results suggest that combined use of S-PRG filler-containing paste and a mouthguard is effective for remineralization of WSLs observed on numerous teeth.

Acetate sheets in the standardization of intralesional therapy in dermatology.

Acetate sheets in the standardization of intralesional therapy in dermatology.

Control and study of bio-inspired quadrupedal gaits on an underactuated miniature robot

This paper presents a linear quadratic Gaussian (LQG) controller for controlling the gait of a miniature, foldable quadruped robot with individually actuated and controlled legs (MinIAQ-III). The controller is implemented on a palm-size robot made by folding an acetate sheet. MinIAQ-III has four DC motors for actuation and four rotary sensors for feedback. It is one of the few untethered robots on a miniature scale capable of working with different gaits with the help of its individually-actuated legs and the developed controller. The presented LQG controller controls each leg’s positions and rotational speeds by measuring the positions and estimating the rotational speeds, respectively. With the precise gait control on the robot, we demonstrate different gaits inspired by quadrupeds in nature and compare the simulation and experiment results for some of the gaits. An extensive simulation environment developed for robot dynamics helps us to predict the locomotion behavior of the robot in various environments. The match between the simulation and the experiment results shows that the proposed LQG controller can successfully control the miniature robot’s gaits. We also conduct a case study that shows the potential to use the simulation to achieve different robot behavior. In a case study, we present our robot performing a prancing similar to horses. We use the simulation environment to find the required motor configuration phases and physical parameters, which can make our robot prance. After finding the parameters in simulation, we replicate the configuration in our robot and observe the robot making the same moves as the simulation.

Reproducibility of linear and angular cephalometric measurements obtained by an artificial-intelligence assisted software (WebCeph) in comparison with digital software (AutoCEPH) and manual tracing method.

It has been suggested that human errors during manual tracing of linear/angular cephalometric parameters can be eliminated by using computer-aided analysis. The landmarks, however, are located manually and the computer system completes the analysis. With the advent of Artificial Intelligence in the field of Dentistry, automatic location of the landmarks has become a promising tool in digital Orthodontics. Fifty pretreatment lateral cephalograms obtained from the Orthodontic department of SRM dental college (India) were used. Analysis were done by the same investigator using the following methods: WebCeph™, AutoCEPH© for Windows or manual tracing. Landmark identification was carried out automatically by Artificial Intelligence in WebCeph™ and with a mouse driven cursor in AutoCEPH©, and manually using acetate sheet and 0.3-mm pencil, ruler and a protractor. The mean differences of the cephalometric parameters obtained between the three methods were calculated using ANOVA with statistical significance set at p<0.05. Intraclass correlation coefficient (ICC) was used to determine both reproducibility and agreement between linear and angular measurements obtained from the three methods and intrarater reliability of repeated measurements. ICC value of >0.75 indicated good agreement. Intraclass correlation coefficient between the three groups was >0.830, showing good level of agreement, and the value within each group was >0.950, indicating high intrarater reliability. Artificial Intelligence assisted software showed good agreement with AutoCEPH© and manual tracing for all the cephalometric measurements.

Influence of intraoral conditions on the accuracy of digital and conventional implant impression techniques for two-implant-supported fixed dental prostheses.

To compare the trueness and precision of different impression techniques for two-implant-supported fixed dental prostheses between extraoral and intraoral conditions at different locations. Six volunteers participated in this study. A resin block with two parallel analogs was fabricated as an implant site simulator (ISS). The ISS was bonded to a molded ethylene vinyl acetate sheet to create a reference model. For each participant, four reference models were prepared based on the locations of the ISSs: maxillary posterior/anterior region (MaxP/MaxA) and mandibular posterior/anterior region (ManP/ManA). Five impressions were taken extraorally using the open-tray (conventional implant impression technique, CIT) and intraoral scanning (digital implant impression technique, DIT) techniques. The reference models were positioned in the participants' mouths, and impressions were obtained intraorally using the CIT and DIT. The interanalog distance (d) and angulation (θ) were measured to calculate trueness (Δd, Δθ) and precision (dP, θP). Two-way ANOVA and t tests were performed (α=0.05). For the DIT, under intraoral conditions, the Δd and Δθ in MaxP and Δθ in ManP were significantly higher than those under extraoral conditions. For the CIT, under intraoral conditions, the Δd and Δθ in ManA and ManP and Δθ in MaxP were significantly lower than those under extraoral conditions. No significant differences in the dP and θP of either DIT or CIT were observed between the two conditions. Intraoral conditions affected the trueness of DIT and CIT in different regions but had no influence on precision.

Difference in thickness of vacuum-formed mouthguards using ethylene vinyl acetate and polyolefin sheets.

Polyolefin sheets are fabricated in the same manner as ethylene vinyl acetate sheets. The aim of this study was to examine the difference of vacuum-formed mouthguard thickness according to each heating condition using ethylene vinyl acetate and polyolefin sheets. Mouthguard sheets of 3.0 mm ethylene vinyl acetate and polyolefin were vacuum-formed on working models at three heating temperatures: 85, 95, and 105°C. The thickness of the mouthguard was measured at the labial surface of the central incisor, the buccal surface of the first molar, and occlusal surface of the first molar. Differences in the thickness of the mouthguards according to the sheet materials and the heating conditions were analyzed by two-way analysis of variance. Mouthguard thickness varied between the ethylene vinyl acetate and the polyolefin sheets (p < .01), and the thickness of the ethylene vinyl acetate sheet was greater than that of the polyolefin sheet at all heating conditions. The thicknesses of mouthguards fabricated using the ethylene vinyl acetate and the polyolefin sheets were not different for the three heating conditions in this study. The thickness was greater for mouthguards fabricated using ethylene vinyl acetate sheet than when polyolefin sheet was used. The thickness of the mouthguards was not different for the three heating temperatures for both the ethylene vinyl acetate and the polyolefin sheets.

Effects of mouthguard and paste containing S-PRG filler on remineralization of artificial subsurface carious lesions

The aim of this in vitro study was to evaluate the remineralization effects of ethylene-vinyl acetate (EVA) sheet (sample; SHOFU) and paste (PRG Pro-Care Gel®; SHOFU) containing surface pre-reacted glass-ionomer (S-PRG) filler. Extracted human premolars were decalcified to create subsurface carious lesions on the buccal side. Decalcified tooth specimens were then covered by EVA sheets with two different S-PRG filler contents either with application of paste (PRG MG-Paste and EVA MG-Paste groups) or without application of paste (PRG MG and EVA MG groups), then immersed in a remineralization solution. Control group teeth were not covered with any mouthguard and did not receive application of paste. Micro-CT (μCT) images of the teeth before and after the remineralization process were obtained to compare mineral gains. The percentage remineralization (%R) of each group was calculated using the mineral density (MD) profile from μCT. The microstructure of the tooth surface was observed under scanning electron microscopy, and constituent elements were examined using an electron probe micro-analyzer. The PRG MG group showed a significantly higher %R than the Control or EVA MG groups. The PRG MG-Paste group showed a significantly higher %R than the PRG MG group. In the PRG MG-Paste group, small precipitations were observed on tooth surface, and silica and aluminum were detected. The combination use of S-PRG filler containing EVA sheet and PRG Pro-Care Gel exhibits a synergetic effect on remineralization of pre-cavitation carious lesions.

Path Tracking and Connection Mechanism of a Reconfigurable, Foldable, Legged, and Miniature Robot

This work introduces the reconfigurable, foldable, legged, and miniature robot (REMIRO), a palm-size modular robot with compliant c-shaped legs. The robot’s body modules are made by folding acetate sheets. The legs connected to these modules are made of Polydimethylsiloxane (PDMS) using molding. The backbone modules are made of Thermoplastic polyurethane (TPU) using 3D printing. In this study, we propose a path tracking algorithm for our robot that enables our modules to move from a random initial location to the pose required to lock with another module. We also design and manufacture backbones with embedded permanent magnets to allow connection between modules. We also present a kinematic model of our robot utilizing c-shaped leg kinematics, predicting the forward differential kinematics of the robot, which is then used to test the path tracking algorithm. Our experiments show that the proposed path tracking algorithm moves our robot to the desired location with an average positioning error of 5mm and an average orientation error of 22°, which are small enough to permit docking between modules.

Development of New Simple Compositions of Silver Inks for the Preparation of Pseudo-Reference Electrodes.

Silver materials are known to present excellent properties, such as high electrical and thermal conductivity as well as chemical stability. Silver-based inks have drawn a lot of attention for being compatible with various substrates, which can be used in the production uniform and stable pseudo-reference electrodes with low curing temperatures. Furthermore, the interest in the use of disposable electrodes has been increasing due to the low cost and the possibility of their use in point-of-care and point-of-need situations. Thus, in this work, two new inks were developed using Ag as conductive material and colorless polymers (nail polish (NP) and shellac (SL)), and applied to different substrates (screen-printed electrodes, acetate sheets, and 3D-printed electrodes) to verify the performance of the proposed inks. Measurements attained with open circuit potential (OCP) attested to the stability of the potential of the pseudo-reference proposed for 1 h. Analytical curves for β-estradiol were also obtained using the devices prepared with the proposed inks as pseudo-references electrodes, which presented satisfactory results concerning the potential stability (RSD < 2.6%). These inks are simple to prepare and present great alternatives for the development of pseudo-reference electrodes useful in the construction of disposable electrochemical systems.

Education

This issue contains two papers in the Education section. The first paper, “Computed Origami Tomography,” is presented by Axel Kittenberger, Leonidas Mindrinos, and Otmar Scherzer. The paper is motivated by advances in scanner technology and the increased sophistication of the accompanying 3D image reconstruction methods. The authors have implemented the idea of constructing a system that eliminates dangerous X-ray radiation but preserves the main features of CT scanners. Such a system is safe to use in training. The proposal is to replace the X-rays with optical illumination and detection of thin objects that are translucent in the visible spectrum. The origami figures, which are made out of thin sheets of cellulose acetate, become an attractive surrogate model for the objects in real CT scans. The first part of the paper contains an explanation of the physics assumptions and laws on which the X-ray tomography is based. The theory of light-ray propagation is similar to the theory of X-rays and provides a geometric optics approximation. The second part of the paper contains instructions for building a crafting device that can record digital images of small 3D objects at different rotation directions. Open source software for reconstructing the 3D object from the collected images is provided. An introduction to cryo-imaging and cryo-EM data provides additional insight into new directions in computerized tomography (``cryo” means “cold” in Greek). In this context, “cryo” refers to the process of immobilizing a sample specimen (a virus or a molecular cluster in a cell) by freezing it. The authors maintain that the described setup allows for conducting tomographic imaging experiments even at home. They have offered a training course along the lines of this paper multiple times and have produced a YouTube video explaining the basic ideas (the link to the video is included in the reference list). For those who wish to experiment with computational tomographic reconstructions without assembling the device, the authors have a database of several objects together with their tomographic measurements. The paper is written in an engaging style, focusing on the main ideas and pointing to further references. The second paper, authored by Bernardo Gouveia and Howard A. Stone, is “Generating Resonant and Repeated Root Solutions to Ordinary Differential Equations Using Perturbation Methods.” The paper highlights a general, very flexible, yet relatively simple method to construct a resonant or repeated root solution to ordinary differential equations (ODEs). The idea of the method is to introduce a small parameter $\epsilon$ in the forcing function and then to construct a suitable Taylor expansion of a known homogeneous solution in that parameter. Next to the natural desire to analyze any situation mathematically, unwanted oscillations are highly relevant in civil engineering and other areas. Therefore, software systems provide solutions addressing resonance, but the results might be cumbersome or not insightful at times. The paper starts with background material on methods to obtain resonant solutions or repeated root solutions to ODEs. Then the authors present seven examples of increasing complexity, on which the ideas are developed and the advocated approach is explained. In the context of some of those examples, the advantages of the method are illustrated by comparison of its solutions to the solutions obtained by Mathematica. The concluding section of the paper contains a more general derivation, which encompasses all of the examples discussed before. The authors assert that the method is beneficial to students as well as to practitioners who come across this type of problem in their work. The paper is written in a clear and deductive manner.

The use of light-transparent acetate sheet to measure canopy height of marandu palisadegrass: the influence of development stage and sward height

The use of light-transparent acetate sheet (LAS) may generate variations in the height measured in the sward. However, we compared the use or non-use of LAS to measure the average sward height of marandu palisadegrass (Urochloa brizantha syn. Brachiaria brizantha cv. Marandu) pastures. In the first experiment, the methods were applied in pastures with different average heights (15, 25, 35, and 45 cm), managed under continuous stocking with sheep, and with predominance of vegetative tillers. The shorter pastures (15 and 25 cm) had similar heights with or without the use of the LAS. However, in the taller pastures (35 and 45 cm), the use of LAS resulted in lower height values, compared with its absence. In the second experiment, we compared both methods for measuring the height of deferred marandu palisadegrass and fertilized with two nitrogen levels (50 and 200 kg ha-1) and with high presence of reproductive tillers. A completely randomized design with four replicates was adopted. With 200 kg ha-1 of N, the canopy height was greater than when it was fertilized with 50 kg ha-1 of N. With the use of LAS, the height of deferred and reproductive canopy was greater than without it. In a taller marandu palisadegrass pasture with predominance of vegetative tillers, the use of LAS results in smaller height, contrary to what occurs in deferred swards with reproductive tillers.

Ballooned glove for smooth epidermal graft transfer in vitiligo

Suction blister epidermal grafting is a popular modality of surgical treatment in vitiligo. However, the suction blister epidermal grafts being thin causes difficulty in transfer from the donor site to the recipient site. Various tools have been suggested for graft transfer, like fine gauze, the use of gloved fingers, glass slides, and acetate sheets. These modalities have their own advantages and disadvantages. For example, a glass slide is rigid and difficult for curved surfaces of recipient sites, 1 Ashique K.T. Kaliyadan F. When half-slide can deliver double efficiency for blister grafting in vitiligo. J Am Acad Dermatol. 2020; 83: e181-e182https://doi.org/10.1016/j.jaad.2019.04.056 Google Scholar acetate sheets are not firm enough, and a gloved finger provides a small surface area. 2 Laxmisha C. Thappa D.M. Surgical Pearl: gloved finger as a transport platform for epidermal graft of suction blister. J Am Acad Dermatol. 2007; 57: S118-S119https://doi.org/10.1016/j.jaad.2005.04.022 Google Scholar To overcome these problems, we suggest using a ballooned glove to transfer suction blister epidermal grafts from the donor to recipient site.

Effective thermoforming method for maintaining mouthguard thickness with a circular sheet using a circular frame.

Mouthguard thickness is important to prevent oral and facial trauma during sports. The aim of this study was to establish an effective thermoforming method for maintaining mouthguard thickness with a circular sheet using a circular frame. Mouthguards were thermoformed using 4.0-mm-thick ethylene vinyl acetate sheets and a vacuum forming machine. Each sheet was pinched at the top and bottom and stabilized by a circular frame. Two heating conditions were compared: (1) condition N, where the sheet was formed when it sagged 10mm below the level of the sheet frame at the top of the post, and (2) condition L, where the sheet frame was lowered 50mm below the ordinary level and heated, and the sheet was formed when it sagged 10mm. In each heating method, two forming conditions were compared: (1) when the sheet softened, the sheet frame was lowered and formed (condition C; N-C, L-C), and (2) after the sheet frame was lowered, the model was moved forward 20mm and then formed (condition MP; N-MP, L-MP). Six mouthguards were fabricated for each condition. Thickness differences due to heating conditions and forming conditions were analyzed by the two-way ANOVA and Bonferroni's multiple comparison test. At the incisal edge and at the labial and buccal surfaces, significant differences were observed among all conditions, and the thicknesses were in the order N-C < L-C < N-MP <L-MP. At the cusp, significant differences were not observed depending on the heating conditions. The thermoforming method with a circular sheet using a circular frame did not maintain a sufficient thickness only by the method of moving the model position just before formation. However, the results suggest that a single-layer mouthguard with a labial thickness of 3mm or more could be fabricated by applying the method of lowering the sheet frame and heating the sheet.

A buckling-sheet ring oscillator for electronics-free, multimodal locomotion.

Locomotion of soft robots typically relies on control of multiple inflatable actuators by electronic computers and hard valves. Soft pneumatic oscillators can reduce the demand on controllers by generating complex movements required for locomotion from a single, constant input pressure, but either have been constrained to low rates of flow of air or have required complex fabrication processes. Here, we describe a pneumatic oscillator fabricated from flexible, but inextensible, sheets that provides high rates of airflow for practical locomotion by combining three instabilities: out-of-plane buckling of the sheets, kinking of tubing attached to the sheets, and a system-level instability resulting from connection of an odd number of pneumatic inverters made from these sheets in a loop. This device, which we call a "buckling-sheet ring oscillator" (BRO), directly generates movement from its own interaction with its surroundings and consists only of readily available materials assembled in a simple process-specifically, stacking acetate sheets, nylon film, and double-sided tape, and attaching an elastomeric tube. A device incorporating a BRO is capable of both translational and rotational motion over varied terrain (even without a tether) and can climb upward against gravity and downward against the buoyant force encountered under water.