This PDF file contains the front matter associated with SPIE Proceedings Volume 10597, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Antennas made using rigid substrates are unsuitable in applications where space and surface conformability are a concern. This is a common issue for RFID, smart tags and wearable electronics applications which require conformability to the mounting structure, in addition to being weather-proof. Commercially available designs employ bendable substrates such as synthetic rubber, polymer, microfluids and plastics, but these materials are costly, at times difficult to manufacture, and offer limited electrical and mechanical properties. More importantly they are not environmental-friendly. On the other hand, natural rubber is abundant and easily produced. Being a natural product, they are weather-proof and environmental-friendly, the electrical properties are easily controlled and are stable at elevated frequencies. It is also one of the most flexible natural material available and yet can be designed to almost any shape. We report for the first time in this paper detailed characterization of RFID antennas based on natural rubber formulated with carbon black filler. Prototype patch and meander dipole antennas were simulated using CST Microwave Studio to operate at 921 MHz, using copper as the conductor and natural rubber as the substrate. Full characterization using scattering parameters and radiation patterns were carried out for flat and bent conditions. The prototypes offered performances comparable to existing designs which use synthetic materials, with maximum read range of about 1.8 m. Optimum processing conditions and the effects of material on the antenna performance are described here. The performance obtained is comparable to commercially-available designs, with added benefits offered by a natural material.

In this study, the optimum structure of a shear type accelerometer is designed to maximize the performance of a vector hydrophone used for a towed array sonar system. The effect of the structural elements of the accelerometer on the receiving voltage sensitivity (RVS) of the hydrophone is analyzed, and the optimal structure of the accelerometer is derived based on the analysis. The RVS of the acceleration designed by the optimization is -204.9 dB, which satisfies the design specification. In addition, it is confirmed that the accelerometer with the optimum structure has the dipole mode beam pattern required for a vector hydrophone. The dipole response when coupled with an omnidirectional hydrophone can generate a cardioid beam pattern that can detect not only magnitude of a sound pressure but also the direction of the external sound source. Precedent works have presented the concept of the vector hydrophone and proved its functionality without detailed design of its structure so far. This work is new in that we carried out full detailed design process to maximize the performance of the vector hydrophone based on the analysis of the effect of structural parameters constituting the accelerometer.

Irregularities in process conditions during powder bed fusion (PBF) additive manufacturing (AM) can lead to localized defects and poor part quality. At the same time, because PBF-AM is a layer-by-layer process, material properties such as defect concentration can be characterized in situ, thus providing an opportunity to ‘qualify as you build.’ Here we review methods based on high speed, multi-wavelength optical measurements of melt pool evolution, material ejection and layer-to-layer height variation during PBF processing, and compare the results to ex situ x-ray tomographic measurements. We also discuss the complex mechanisms related to the interaction between the melt pool, laser beam, and powder bed which ultimately drive defect formation. Along with providing process monitoring data to facilitate part certification, data provided by in situ optical diagnostics can help validate process models. The practical implementation of these high speed diagnostics into commercial platforms is also discussed. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

In this research, we propose a new monitoring method of the temperature of the molten pool for stable layered fabrication in the metal wire supply type laser 3D printer. The metal wire to be supplied is melted by the laser during molding and flows into the molten pool of the base metal, so that an electric closed circuit is formed. At that time, since the temperature of the molten pool exceeds 1400 ° C., when the metal wire and the base metal components are different, the Seebeck effect produces an output voltage between the base metal and the molten pool and metal wire. From this output voltage, the temperature of the molten ground can be obtained. Furthermore, by applying this method, it is also possible to monitor the component ratio of the gradient material from the voltage generated between each metal wire and the base material when a plurality of different wires are supplied and a gradient material is produced .

In this paper, we demonstrate the fabrication of a chemical sensor for 2,4-dinitrotoluene (DNT), based on an opticalfiber- microsphere coated with upconversion nanocrystals functionalized with layers of polyelectrolytes - poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH). The design consists of a microsphere, which supports whispering-gallery-modes (WGM), coupled to an optical fiber. The NaYF₄-Yb³⁺,Er³⁺ nanocrystals have a bright fluorescence around 550 nm and 650 nm when irradiated with 980 nm, which is enhanced by the WGM. When functionalized with PAA/PAH layers, these nanocrystals can be coated on the microsphere with control over layer thickness. The presence of DNT on the surface of the microsphere quenches the fluorescence as the absorption spectrum of DNT has peaks in 500 - 600 nm. The effect of concentration of the analyte on the magnitude of quenching has been studied. The paper discusses the design, fabrication and characterization of the chemical sensor.

We report here the characterization of graphene at microwave frequencies using an improved on-wafer calibration method which did not require 50 Ω loads. Multi-layer graphene films about 3 nm thick were grown on Ni-coated Si wafers using TCVD. Co-planar transmission lines of dimension 250 μm × 30 μm were constructed from the graphene films. Scattering parameters up to 20 GHz were measured using on-wafer probes, and SOLT (short-open-load-thru), LRM (load-reflect-match) and TRL (thru-reflect-line) on-wafer calibration methods were used to enable comparison. The microwave properties were modeled by a physics-based resistor-inductor-capacitor (RLC) lumped element equivalent circuit, frm which the conductivity of bi-layer and multi-layer graphene was extracted. Our study showed modeling using TRL is more accurate, and the conductivity of graphene extracted from our model was found to be 3.2 ×10⁴ S/m, which is better than those reported by others. Our work revealed improved graphene characterization at high frequencies since a better calibration was used here.

In this paper, we present our study on developing a P(VDF-TrFE) pressure sensor for the application of small strain sensing. P(VDF-TrFE) has an excellent chemical resistance, biocompatibility, flexibility, electrostatic and piezoelectric characteristics. It can be applied for personalized health monitoring, such as heart rate and blood pressure monitoring. To measure the small strain generated by a soft tissue, we develop a flexible pressure sensor based on highly aligned electrospun P(VDF-TrFE) micro-fibers. Both electrostatic and piezoelectric sensing methods were studied. We use a drum collector to create a highly aligned fibers, and use annealing and corona discharge to enhance β phase of P(VDF-TrFE) fibers. The electrodes that we design was 10 mm square, and sensitivities of electrostatic and piezoelectric signals were studied. A 4-point bending test was used to perform small strain measurement. Our experimental finding demonstrated that the sensitivity of sensor with fibers in parallel with bending direction was 5.39 × 10⁻² 𝑝𝐴/με., The sensitivity of sensor with fibers in perpendicular with bending direction was 2.38 × 10⁻² pA/με. The sensitivity of parallel fibers was 2.26 times higher than the perpendicular fibers. Furthermore, we verified that after removing electrostatic charges in the P(VDF-TrFE) membrane, the major contribution of the parallel aligned sensor was piezoelectric effect. The P(VDF-TrFE) pressure sensor has about 80% of piezoelectric effect and about 20% of electrostatic effect. On the other hand, both electrostatic and piezoelectric properties contribute to the sensitivity in perpendicular aligned pressure sensor.

Cellulose nanofiber (CNF) is an impressive bio resource mainly because of its high mechanical strength, stiffness and optical transparency, which is promising for eco-friendly structural materials. This paper presents the possibility of ecofriendly thin films made with CNF, which has strong, flexible, transparent and lightweight behaviors. The fabrication of thin CNF film and its properties are investigated. Fabrication is carried out by tape casting method to control thickness, followed by separation and drying. Its chemical structure and physical interaction were investigated using Fourier transform infra-red spectroscopy. Mechanical properties are investigated by a tensile test. 3 micron thick CNF film is successfully fabricated. The prepared CNF film is applicable for structural materials in space applications.

Hybridization of organic and inorganic material opens many opportunities by taking the advantages of both materials. Cellulose is one of the most abundant material on earth which is biocompatible, cheap, lightweight, and environment friendly. Cellulose nanofibers (CNF) have high mechanical strength because of high crystallinity. Graphene Oxide (GO) is one forms of carbon which is produced from graphite flake. CNF and GO composites (CNFGO) can offer advantages in terms of mechanical strength as well as electrical properties. CNF is extracted from hardwood pulp using mild TEMPO treatment and aqueous counter collision (ACC). GO is synthesized from graphite flakes following improved synthesize of graphene oxide. CNFGO suspension is prepared using a simple blending method. CNFGO fiber is fabricated by spinning CNFGO suspension in CaCl₂ coagulation solution. The composite fiber is characterized using Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR), X-Ray Diffraction (XRD). Mechanical Properties of the composite fibers is also investigated.

The Army continues the development of 3D printing technology to enhance the capability to produce smaller and lighter precision weaponry. Researchers and support organizations that are affiliated with the Army Aviation and Missile Research, Development, and Engineering Center (AMRDEC) are developing nano-based structures and components for advanced weaponry, aviation, and autonomous air/ground systems applications. The first key area consists of determining in-plane and out-of-plane shear properties of test articles made by 3D printing (Fused Deposition Modeling - FDM) and comparing to the conventional extrusion/forming sheet process. Test specimens are made from three polymer materials: acrylonitrile butadiene styrene (ABS), high impact poly-styrene (HIPS), and poly-lactic acid (PLA). Laboratory testing is performed according to the ASTM D3846–02 method for determining the in-plane shear strength, while the ASTM D5379 method is used for determining the out-of-plane shear properties. A description on how the 3D printing process advances the shear properties and has the potential of improving the in-plane and cross-sectional shear properties over the conventional manufacturing process is presented. The second key area demonstrates a set of materials, processes, and techniques that support the enabling of additive manufacture (AM) of RF components. Research activities are focused on developing open-source hardware/software multi-material direct digital printing, and producing 3D printed antenna, passive components, and connectors for C-band and Ku-band systems. Material studies have demonstrated a suitable material set for RF components and identified key material performance limits. Results show how more enhancement could be achieved by optimizing the variables that affect 3D printing.

We are developing a Multi Material 3D printer to print an object with different kind of soft and hard material in a single run. It is expected that the combination of printing soft and hard material will be a new kind of 3D printer. Our main printing material is conductive based soft filament made by our laboratory “Soft and Wet Matter Engineering Laboratory”, other different soft filament and hard plastic filament to create fully functional, multi material objects in a single printing run with greater variety and lower cost than other single material printing. In addition, we are developing a special type of Extruder, by using this we will be able to print both soft and hard material with one printer. This will be a new era of 3D printer. Such kind of 3D printer will possibly be a good STEM tool in medical sector and robotics.

In recent years, the development of high strength gel has progressed, and it is entering the stage of trying to apply it to mechanical parts making full use of the low friction property of gel. If this is realized, further increase in energy efficiency is expected. DN gel has high strength and low friction. We are aiming at practical application as P type O-ring utilizing this performance. In this study, a vertical rotation type testing machine was introduced, and friction measurement was performed under conditions assuming helical motion.

In the radiation therapy, ionization chambers and/or film dosimeters are usually used to measure dose distribution, and three-dimensional absorbed dose distribution of the human body is calculated by computer simulation. However, at the treatment site, measurements of actual three-dimensional absorbed dose distribution become more important, because the commission of radiation therapy apparatus of high-precision, SRT, IMRT, IGMRT and so on, are important. Gel dosimeter can be directly used as water equivalent phantom, and using 3D gel printer, radiation sensitive artificial organs are expected to see the absorbed dose distribution directly. In this research, we developed a gel dosimeter by polymer chain cleavage mechanism using 3D printable gels and a device measuring the internal structure of gels., and development of 3D printable gel dosimeter using polymeric polymerization .We could not find any differences of internal structure of gels by our original DLS apparatus, but we have confirmed that tested gels are stable in usual dose level of radiation therapy. In addition, by developing of 3D printable gel dosimeter using polymeric polymerization, we succeeded to make dose distributions by using UV light.

Conventional manufacturing techniques include removing the excess materials to get the desired shapes; however, additive manufacturing include direct manufacturing of the objects using computer aided design model through adding a layer of material at a time. Strength and durability of the final products are important issues in designing 3D printed functional objects. Primary considerations of 3D printing process include some specifications of the printing process, printing orientation, materials selection and overall design (complexity, size, pore volume and shape). Infill structures are printed in selected patterns with a desired solid percentage, which is arranged using the slicing software. Percent rate and designed pattern are two key parameters for infill specimens which affect the print time, material usage, weight, strength, and decorative assets, as well. Polylactic acid (PLA) is a biodegradable and bioactive thermoplastic derived from renewable resources, such as corn starch, sugarcane, cassava and so on. In this study, five different infill shapes (e.g., solid, diamond, hexagonal, square, and triangle) of PLA were designed using CATIA program, and then 3D printed with 20, 40, 60, 80 and 100 vol.% to determine the effects of the infill shapes on the compressive strengths of the materials. The purpose of this study is to investigate the infill shapes, volumes, and orientation of infill shapes in the 3D printed specimens. Compression test results showed that infill shapes and volume percentages affect the mechanical properties of the 3D printed parts. This study indicated that mechanical properties of 3D printed materials could be maximized using the different infill shapes and volume percentages in 3D printing process.

Hydrogels are three-dimensional polymeric networks capable of absorbing large amounts of water or biological fluids. Due to their high water content, porosity and low friction they closely simulate natural living tissue. The properties of a polymer gel depend on the chemical structures of the component molecule and can be controlled or tuned by external stimuli such as heat, optics, solvent, and pH. Shape-memory gels (SMGs) are unique materials that have the ability to return from a temporary deformed state to their permanent i.e. original shape induced by an external stimulus like temperature change. Poly(dimethyl acrylamide-co-stearyl acrylate) (DMMA-co-SA)-based SMGs show such behavior with high mechanical strength, transparency and moderate water content (≈30wt%). In this work, we applied stereolithography process to fabricate DMMA-co-SA SMGs and printed sample models like gel sheets and tubes. However, printing a transparent SMG was not an easy task due to several problems like sample turbidity, swelling during printing and shape deformation. We critically maintained these uses and compared the properties of 3D printed SMGs with that of conventionally synthesized SMGs. Finally, we analyzed the limitation and potential of 3D printing process and discussed a suitable approach for application of 3D printed SMGs as an actuator.

Cellulose nanocrystal (CNC) is known to be a good source for structural material due to its impressively high mechanical properties and it is also an excellent dielectric filler due to its electrical polarity originated from its crystal structure. This paper reports a soft electro-active polymer made by blending CNC with poly(urethane), which is named as CPPU. CPPU is an electro-active dielectric elastomer, applicable for smart and active lens. In CPPU, CNC plays the role of filler that improves dielectric constant. For homogeneous distribution of CNC in poly(urethane) matrix, hydrogen boned CNCpoly[di(ethylene glycol) adipate] (PDEGA) was prepared by simple blending as diol of urethane bond. Hexamethylene diisocyanate was used for isocyanate salt as cross-linker. The prepared CPPU exhibits high transparency above 90% and excellent dielectric constant. As a result, the CPPU dielectric elastomer shows large deformation under low electric field. Transparency and large deformation behaviors of CPPU are attractive for smart and active lens applications.

This paper reports an eco-friendly nanocomposite made with bamboo cellulose nanofiber and chitin micronanofibers. Bamboo has antibacterial property and is beneficial for human living environment meanwhile chitin is safe for food packaging, highly toxic resistant and able to absorb heavy metals. Chitin was micro-nano fibrillated (CT-MNF) by using aqueous counter collision (ACC) physical method. Cellulose nanofiber (CNF) was isolated from bamboo by treating it with 2,2,6,6-tetramethylpiperidine-1-oxylradical (TEMPO)-oxidation followed by ACC method. Bamboo cellulose nanofiber (BA-CNF) was blended with CT-MNF to form BA-CNF nanocomposite. The morphology of BA-CNF and CT-MNF was determined by an atomic force microscopy and field emission scanning electron microscopy. CT-BA nanocomposites were made with different ratios of BA-CNF and CT-MNF. Properties of CT-BA nanocomposites were investigated by using thermogravimetric analysis, UV-visible spectra, and tensile test. The UV-Vis visible spectrum shows better transmittance of the CT-BA nanocomposite with high BA-CNF content. CT-BA nanocomposite has better surface smoothness. By blending BA-CNF with CT-MNF, CT-BA nanocomposite shows improved mechanical properties.

Atomic force microscopy (AFM) is known for measuring the mechanical properties of nanomaterials. It has been used for measuring the mechanical properties of few kinds of fibers, such as carbon nanotubes, gold nanofibers, graphene. In this study, the effect of various sources on the elastic modulus of cellulose nanofibers (CNFs) was investigated by using AFM three-points bending test. The CNFs were extracted from hardwood, softwood, bamboo and cotton by using aqueous counter collision (ACC) system and the morphology of CNFs were studied by AFM. CNFs were successfully transferred to the AFM calibration chip and the three-points bending test was performed. CNFs were considered to be circular shape by taking into account the AFM tip radius and the Young’s modulus was calculated. The calculation results indicate that the range of Young’s modulus is between 102 and 131 GPa varying upon the cellulose resources.

The fabrication of cellulose long-fiber (CL) is necessary for eco-friendly and high strength composites development. CL can be made with cellulose nanofiber (CNF) that has high mechanical strength and modulus. However, the mechanical properties of CL in early studies were shown to be lower than those of original CNF. An idea of fabricating strong CL is to align CNFs so as to make strong hydrogen bond between CNFs. To achieve this, alignment of CNF is very important. In this study, high dc magnetic field is introduced to align the CNFs. The CNFs are aligned perpendicular to the direction of dc magnetic field due to its negative diamagnetic anisotropy. CNFs isolated by TEMPO oxidation and aqueous counter collision method are used in this experiment. The CNF emulsion is located in the high dc magnetic field and cured. Alignment of CNF is investigated by using optical microscopy, scanning electron microscopy and mechanical tensile test.

Ionic liquids (ILs) are fascinating materials with unique physicochemical properties like non-volatility, non-flammability, wide electrochemical window, high thermal stability and high ionic conductivity. They offer numerous possibilities in the fields ranging from electrochemistry to mechanical engineering however their employment in the 3D printing technology is very limited till to date. One of the big challenges of using 3D printing for materials is a careful selection of component material with a perfect concentration and an appropriate method. In this study, we focused on the potential of ILs on 3D printing technology covering the most popular printing methods named fused deposition modeling (FDM) and stereolithography (SLA) process. For FDM process IL-based conductive nanocomposite filaments have been developed and printed via 3D printing process along with their material characterization. In a different approach, ionic gels in IL medium have been successfully printed by SLA process with precise structures of microscale resolution. Conductive, mechanical and other physicochemical properties have been explored to get the proper understanding of the ionic gel materials.

Gels, soft and wet materials, have unique properties such as transparency, biocompatibility, and low friction. In recent years, high strength gel has been developed. Various studies take advantage of these characteristics has proceeded, we research to use high strength gel. High-strength gels are expected to be put to practical use in various situations. For example, gel organ models and gel artificial blood vessels are required at a medical site. Also in the field of robotics, soft materials are drawing attention. To put a high-strength gel into practical use, it is necessary to free-form a gel using a 3D gel printer. We developed a 3D gel Printer "SWIM-ER", has enabled modeling of complex shapes of the gel. However, this is expensive. Therefore not all of the gel researchers and the companies have such a device. “RepRap” is the abbreviation for “Replicating rapidly prototyper”, the open source 3D printer. Most of the RepRap parts are made of a resin, and the 3D digital data of the parts and its firmware are posted on the internet. Therefore, we can easily create another 3D printer by building the parts with a 3D printer and programing the firmware on an inexpensive electronic substrate like the “Arduino”. In this research, we aimed to develop a low-cost 3D gel printer which can be used by anyone.

Yamagata University established the Soft-Matter Robotics Consortium (SOFUMO) to study the extreme parts of robots and to construct epoch-making soft robots using such extreme parts. As a part of such effort, we study a gel piezoelectric sensor and construct a jellyfish-like robot using gel materials such as ion gel, composed of polymer network and ionic liquid, and shape memory gel. We revealed that the ion gel is more appropriate for pressure sensor that particle-doublenetwork hydrogel since impedance of ion gel is changed by application of load weights. In addition, the jellyfish-like robot was constructed using hydrogel and shrinkable wire using electric power. These techniques are expected to be applied to epoch-making soft-matter robots.

3D printers are mainly used to make "things" by using synthetic resin as materials, but recently 3D food printers that make "food" such as pizza and chocolate which were developed and became a hot topic. However, these 3D printers are adapted to only one material, which is difficult to shape in various food materials. Therefore, we developed a multimaterial 3D food printer "FP-2400" that can be applied to other food materials.

Many 3D food printers are syringe pump based, but FP-2400 is screw based. This is a very new type of 3D food printer. By adopting the screw type, it became easy to control the material, as well as possible to use several kinds of materials.

So far, we have succeeded in shaping rice flour gel, bean paste, cookie etc. as food printing materials. It is possible to print with other type of food gel materials, as long as we print like this. The bean paste is a traditional Japanese sweet, and sometimes many customers like to take printed food at the exhibition. Eating 3D-shaped foods are sometimes fun, and it is becoming popular around the world.

In the future, our aim to be able to design not only shape but also will think about nutrition, taste and texture with 3D food printer. We believe that this technology can be applied to nursing care and hospital foods that require special attention and we can prepare meals tailored as their needs.

Poly(vinylidene fluoride) (PVDF) has four crystalline structures (α, β, γ and δ phase structures) in solid state. The extraordinary PVDF electrical properties are directly attributable to its crystalline structure. Only α-phase structure shows no crystal dipole, but this phase structure is converted easily into other phase structures according to some schemes. Generally, PVDF is given uniaxial stretch and polarization processes in order to convert into β-phase or γ- phase structure before sensor and actuator film use. However, we recently found a novel method in which PVDF film structure became β-phase or γ-phase without mechanical deformation processes. Furthermore, this technique enables us to apply printing technology, and realize the creation of free-form 3D sensor and actuators.

In the development of printed PVDF film, the integration of material fabrication technique, its crystalline structure state, forming technology and macroscopic electrical properties will be important research topics. Up to the present, authors have constructed PVDF film fabrication techniques. As a result, PVDF crystalline structure was changeable using the techniques. In addition, some in-house PVDF property measurement systems have been constructed for the sensor and actuator applications. Furthermore, a novel PVDF printer, which can draw freeform 2D PVDF film, has been developed on the basis of PVDF film fabrication results. In present paper, we would introduce our PVDF film fabrication techniques, in-house PVDF property measurement systems and P-p printer.

In this paper, we demonstrate fabrication processes of dual atomic force microscopic (AFM) probe with embedded micro-channels and a nozzle hole for liquid delivering function for 3D printing in nano-scale. The nozzle and embedded micro-channels were successfully fabricated with under-surface connection and hydrophilic inner walls. The narrow trench opening remained above the micro-channel, was completely sealed by combination of Si thermal oxidation and subsequent SiO₂ sputtering deposition. Twin Si tips with an outlet nozzle hole and embedded micro-channel were fabricated with the developed fabrication process.

The specially designed and produced Stealth coating for the aircrafts and for the ships must be effective by their direct tasks against of the radar (by the way for the laser, optical and IR remote control too). But it is not antidote in some cases for the passive device as the microwave radiometers, because their job is to evaluate natural radiation of an object at the background of the environment/s (sky is cold, Earth is warm). More to say such specially calculated surfaces which avoids the vertical ones for the radar beams and reflect this radiation “to the milk” can promote and to be convenient for the remote radiometric detection, because the sky radiates from any direction. For the case of Stealth coating with full microwave absorption it was interesting to do simplest evaluation and background of such possible passive method of the remote sensing at the sample of using the microwave discriminator. Short explanation and the simplest evaluation were performed about possible real distances for the disclosing.

Yeast cells are always used in the biofuel, alcoholic and baking industries. Real-time monitoring of the yeast concentration without any algorithm processing is significant to master the yeast cells surviving condition. Here we demonstrate a new method to monitor the yeast cell concentration using our previous developed microscope—portable microscopy based on fiber-optic array (FOA). The sample is illuminated by a broadband LED and a light diffuser is used to create uniform illumination over the entire field-of-view (FOV). The image pre-processing including the denoising and binarization are used for the images optimization to increase the signal-to-noise ratio (SNR). Automated counting of the yeast cells is performed on a computer using ImageJ. The paper provides a new method for the counting of the yeast cells.

Hand gesture recognition has recently grown as a powerful technical means in human-machine interaction field for control the appliances such as in home automation. However, the accuracy recognition of diverse hand gestures is still in the early stage for real-world application. In this paper, we present a new gesture recognition framework which is capable of classifying ten different hand gestures based on the input signals from surface electromyography (sEMG) sensors. The multi-channel signals of a hand motion are simultaneously captured and transmitted to a PC via Bluetooth wireless protocol. The proposed recognition framework composes of three main steps: gesture sequence segmentation, feature extraction by sparse autoencoder, and deep neural network (DNN) based classification. The advantage of the proposed approach is the automated abstract feature extraction based on sparse autoencoder method. Combined with the DNN classification technique, we could achieve a better recognition performance tested on the dataset consisting of ten types of hand gestures compared with other classification methods.

Soft pressure sensors have a wide range of applications, such as aerodynamic control of cars and unmanned aerial vehicles, navigation of underwater vehicles, and wearable electronics. Existing soft pressure sensors are typically based on capacitive or resistive principles. However, these sensors, made of multiple layers of different materials, tend to delaminate under negative pressures and thus cause sensor failure. In this work, we present the fabrication method for soft capacitive pressure sensors that can reliably detect both positive and negative pressures. The pressure sensor is comprised of one layer of Ecoflex-0030 substrate with cavity channels embedded inside, and two layers of polydimethylsiloxane (PDMS), with two layers of patterned PEDOT:PSS films serving as the electrodes of the sensor. The PEDOT:PSS films are screen printed orthogonally on both sides of the Ecoflex-0030 substrate, and each side is encapsulated by another PDMS layer, which is much stiffer than the Ecoflex-0030 substrate. More importantly, the cavity channels in the Ecoflex-0030 substrate greatly enhance the substrate deformation, hence the capacitive sensor would exhibit remarkable relative change in capacitance when a pressure is applied. Secondly, the encapsulation of PDMS on the Ecoflex substrate protects the electrodes and effectively avoids the delamination problem under negative pressure. In particular, we report the detailed characterization of sensitivity and repeatability of the fabricated pressure sensor for positive and negative pressures of up to 50 kPa. Furthermore, a 12×12 pressure sensor array is fabricated to demonstrate the capability of mapping pressure distributions created by both compressive loads and vacuum suction.

Cellulose is the most naturally occurring biomolecular polymers ensemble into cellulose nanofibers that has both amorphous and crystalline domains in proportions dependent on the source. Cellulose nanofibrils have raised significant interest as excellent structural materials with exceptional mechanical properties. It is important to understand the structure of CNF and its synergy. This study entails molecular dynamics simulations of the cellulose nanofibrils to give insightful understanding of its atomic details in response to temperature. GROningen Machine for Chemical Simulations (GROMACS) is used as the simulations software and All-Atom Optimized Potential for Liquid Simulations (OPLS-AA) force field is chosen for the simulation. To understand the thermally induced structural changes, lattice parameters, crystal density, hydrogen bonding network and other parameters are critically analyzed. The total number of hydrogen bonds is also observed.