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Additively printed circuits provide advantages in reduced waste, rapid prototyping, and versatile flexible substrate choices relative to conventional circuit printing. Copper (Cu) based inks along with intense pulsed light (IPL) sintering can be used in additive circuit printing. However, IPL sintered Cu typically suffer from poor solderability due to high roughness and porosity. To address this, hybrid Cu ink which consists of Cu precursor/nanoparticle was formulated to seed Cu species and fill voids in the sintered structure. Nickel (Ni) electroplating was utilized to further improve surface solderability. Simulations were performed at various electroplating conditions and Cu cathode surface roughness using the multi-physics finite element method. By utilizing a mask during IPL sintering, conductivity was induced in exposed regions; this was utilized to achieve selective Ni-electroplating. Surface morphology and cross section analysis of the electrodes were observed through scanning electron microscopy and a 3D optical profilometer. Energy dispersive X-ray spectroscopy analysis was conducted to investigate changes in surface compositions. ASTM D3359 adhesion testing was performed to examine the adhesion between the electrode and substrate. Solder-electrode shear tests were investigated with a tensile tester to observe the shear strength between solder and electrodes. By utilizing Cu precursors and novel multifaceted approach of IPL sintering, a robust and solderable Ni electroplated conductive Cu printed electrode was achieved. [ABSTRACT FROM AUTHOR]

In this study, an intense pulsed light (IPL) annealing process for a printed multi-layered indium–gallium–zinc–oxide (IGZO) and silver (Ag) electrode structure was developed for a high performance all-printed inorganic thin film transistor (TFT). Through a solution process using IGZO precursor and Ag ink, the bottom gate structure TFT was fabricated. The spin coating method was used to form the IGZO semiconductor layer on a heavily-doped silicon wafer covered with thermally grown silicon dioxide. The annealing process of the IGZO layer utilized an optimized IPL irradiation process. The Ag inks were printed on the IGZO layer by screen printing to form the source and drain (S/D) pattern. This S/D pattern was dried by near infrared radiation (NIR) and the dried S/D pattern was sintered with intense pulsed light by varying the irradiation energy. The performances of the all-printed TFT such as the field effect mobility and on–off ratio electrical transfer properties were measured by a parameter analyzer. The interfacial analysis including the contact resistance and cross-sectional microstructure analysis is essential because diffusion phenomenon can occur during the annealing and sintering process. Consequently, this TFT device showed noteworthy performance (field effect mobility: 7.96 cm2/V s, on/off ratio: 107). This is similar performance compared to a conventional TFT, which is expected to open a new path in the printed metal oxide-based TFT field. [ABSTRACT FROM AUTHOR]

Accurate and non-destructive measurement of thin layer thickness is critical for ensuring the quality and performance of microelectronic devices. In this study, terahertz time-domain spectroscopy (THz-TDS) was used to measure the combined thickness of a silicon wafer and its deposited thin layer without requiring prior knowledge of the individual material properties. The multi-reflected THz signals from the Si wafer were utilized to accurately calculate the actual thickness and optical properties with a 0.19% error. In the reflection measurement, the variation of optical properties was measured according to the thickness of the deposition through the quartz chamber window. To overcome the intrinsic overlapping of the pulse signal through the quartz chamber window, the detection time of unwanted signals was calculated theoretically, and the inspection conditions such as quartz window thickness and distances between the wafer and window were optimized for accurate measurement with THz-TDS. Based on these results, the accuracy of thickness prediction in the thin layer was confirmed with 4.2% of an error. [ABSTRACT FROM AUTHOR]

Computer-controlled optical surfacing provides superior optical fabrication performance with low-cost mass production over conventional method relying heavily on the skills of optician. However, there are still lots of technical issues to be resolved in computer-controlled optical surfacing, and edge effect has been regarded as one of the most challenging tasks for years due to the unpredictable behaviors of a polishing tool. As a polishing tool approaches the edge of the workpiece, the tool-workpiece contact area decreases and this in turn accompanies the tool-workpiece misfit and non-uniform pressure distribution. Thus, the edge effects should be taken into account in deterministic polishing technique. In this paper, we suggest new edge tool influence functions by modeling the velocity and pressure distribution of a polishing tool with eccentric rotation motion. Here, the finite element analysis was used to accurately predict the non-linear behaviors of a polishing tool at the edge. We verified our proposed method by comparisons with experimental results, and it shows considerable resemblance between them. [ABSTRACT FROM AUTHOR]

N-Acyl homoserine lactone (AHL) is a major quorum-sensing signaling molecule in many bacterial species. Quorum-quenching (QQ) enzymes, which degrade such signaling molecules, have attracted much attention as an approach to controlling and preventing bacterial virulence and pathogenesis. However, naturally occurring QQ enzymes show a broad substrate spectrum, raising the concern of unintentionally attenuating beneficial effects by symbiotic bacteria. Here we report the rational design of acyl homoserine lactonase with high substrate specificity. Through docking analysis, we identified three key residues which play a key role in the substrate preference of the enzyme. The key residues were changed in a way that increases hydrophobic contact with a substrate having a short acyl chain (C4-AHL) while generating steric clashes with that containing a long acyl chain (C12-AHL). The resulting mutants exhibited a significantly shifted preference toward a substrate with a short acyl chain. Molecular dynamics simulations suggested that the mutations affect the behavior of a flexible loop, allowing tighter binding of a substrate with a short acyl chain. [ABSTRACT FROM AUTHOR]

Toe joint is known as one of the critical factors in designing a prosthetic foot due to its nonlinear stiffness characteristic. This stiffness characteristic provides a general feeling of springiness in the toe-off and it also affects the ankle kinetics. In this study, the toe part of the prosthetic foot was designed to improve walking performance. The toe joint was implemented as a single part suitable for 3D printing. The various shape factors such as curved shape, bending space, auxetic structure, and bending zone were applied to mimic human foot characteristics. The finite element analysis (FEA) was conducted to simulate terminal stance (from heel-off to toe-off) using the designed prosthetic foot. To find the structure with characteristics similar to the human foot, the optimization was performed based on the toe joint geometries. As a result, the optimized foot showed good agreement with human foot behavior in the toe torque-angle curve. Finally, the simulation conditions were validated by comparing with human walking data and it was confirmed that the designed prosthetic foot structure can implement the human foot function. [ABSTRACT FROM AUTHOR]

In this study, a new way to predict the muscle fatigue and force from Electromyography (EMG) signal for repeated isokinetic exercise is demonstrated. The relationship between cumulative biceps fatigue and EMG signal during repetitive dumbbell curl tasks with constant velocity was investigated with respect to Maximum voluntary contraction (MVC) levels (20 %, 35 %, 50 % and 75 % MVC). The mean integrated EMG and mean frequency per cycle were obtained from the time domain and frequency domain, respectively. The mean IEMG value and mean frequency values were co-plotted in the global EMG index map. Finally, we developed a new algorithm to predict muscle fatigue and force based on a global EMG index map employing mean IEMG and MNF values. The proposed algorithm based on a global EMG index map can be used to simultaneously predict muscle fatigue and force from real-time EMG signals with arbitrary MVC levels. [ABSTRACT FROM AUTHOR]

Cadavers are often used to measure the material properties of muscle via the static tensile loading test. However, the mechanical properties of the cadaver are different from that of in vivo muscle. In this work, a new way to measure the stiffness of in vivo muscle was proposed based on a vibration test combined with measured electromyography (EMG) signals. The stiffness of the biceps brachii muscle during isometric contractions with various weights (0 - 11 kg) was measured from the vibration test utilizing support properties of a spring attached to a mass. The relationship between the load level, the EMG signal, and the muscle stiffness was investigated and a multiple- spring model for biceps brachii muscle was newly suggested. Also, simulation using a commercial bio-mechanics simulation software (LifeMOD) was conducted to verify the developed muscle spring model and the measured stiffness of the in vivo muscle. The in vivo stiffness of the biceps brachii measured experimentally agreed well with the simulation result. [ABSTRACT FROM AUTHOR]

Putrescine finds wide industrial applications in the synthesis of polymers, pharmaceuticals, agrochemicals, and surfactants. Owing to economic and environmental concerns, the microbial production of putrescine has attracted a great deal of attention, and ornithine decarboxylase (ODC) is known to be a key enzyme in the biosynthetic pathway. Herein, we present the design of ODC from Escherichia coli with high catalytic efficiency using a structure-based rational approach. Through a substrate docking into the model structure of the enzyme, we first selected residues that might lead to an increase in catalytic activity. Of the selected residues that are located in the α-helix and the loops constituting the substrate entry site, a mutational analysis of the single mutants identified two key residues, I163 and E165. A combination of two single mutations resulted in a 62.5-fold increase in the catalytic efficiency when compared with the wild-type enzyme. Molecular dynamics simulations of the best mutant revealed that the substrate entry site becomes more flexible through mutations, while stabilizing the formation of the dimeric interface of the enzyme. Our approach can be applied to the design of other decarboxylases with high catalytic efficiency for the production of various chemicals through bio-based processes. [ABSTRACT FROM AUTHOR]

The nhhBAG gene of Rhodococcus rhodochrous M33 that encodes nitrile hydratase (NHase), converting acrylonitrile into acrylamide, was cloned and expressed in Corynebacterium glutamicum under the control of an ilvC promoter. The specific enzyme activity in recombinant C. glutamicum cells was about 13.6 μmol/min/mg dry cell weight (DCW). To overexpress the NHase, five types of plasmid variants were constructed by introducing mutations into 80 nucleotides near the translational initiation region (TIR) of nhhB. Of them, pNBM4 with seven mutations showed the highest NHase activity, exhibiting higher expression levels of NhhB and NhhA than wild-type pNBW33, mainly owing to decreased secondary-structure stability and an introduction of a conserved Shine-Dalgarno sequence in the translational initiation region. In a fed-batch culture of recombinant Corynebacterium cells harboring pNBM4, the cell density reached 53.4 g DCW/L within 18 h, and the specific and total enzyme activities were estimated to be 37.3 μmol/min/mg DCW and 1,992 μmol/min/mL, respectively. The use of recombinant Corynebacterium cells for the production of acrylamide from acrylonitrile resulted in a conversion yield of 93 % and a final acrylamide concentration of 42.5 % within 6 h when the total amount of fed acrylonitrile was 456 g. [ABSTRACT FROM AUTHOR]

Protein dynamics have been suggested to have a crucial role in biomolecular recognition, but the precise molecular mechanisms remain unclear. Herein, we performed single-molecule fluorescence resonance energy transfer measurements for wild-type maltose-binding protein (MBP) and its variants to demonstrate the interplay of conformational dynamics and molecular recognition. Kinetic analysis provided direct evidence that MBP recognizes a ligand through an 'induced-fit' mechanism, not through the generally proposed selection mechanism for proteins with conformational dynamics such as MBP. Our results indicated that the mere presence of intrinsic dynamics is insufficient for a 'selection' mechanism. An energetic analysis of ligand binding implicated the critical role of conformational dynamics in facilitating a structural change that occurs upon ligand binding. [ABSTRACT FROM AUTHOR]

Efficient binding of enzymes onto the electrode surface has been prerequisite for the construction of sensitive biosensors and biochips. Here, a simple and robust construction of electrochemical glucose biosensor based on pyrroloquinoline quinone-glucose dehydrogenase was demonstrated. The glucose biosensor was fabricated by binding the enzyme onto the anionic self-assembled monolayers on gold electrode via electrostatic interactions. The resulting glucose biosensor gave rise to twofold higher detection sensitivity than that by covalent conjugation under the same condition. Surface plasmon resonance and atomic force microscopy analyses revealed that electrostatic binding of the enzyme leads to much higher surface density of the enzyme. This approach will find wide applications to the development of robust enzyme-based biosensors and biochips. [ABSTRACT FROM AUTHOR]