Analysis and Improvement on a Unimodal Haptic PIN-Entry Method

User authentication is a process in which a user of a system proves his/her identity to acquire access permission. An effective user authentication method should be both secure and usable. In an attempt to achieve these two objectives, Bianchi et al. recently proposed novel unimodal PIN-entry methods that use either audio or vibration cues. This paper analyzes the security of their method, in particular, the vibration version of one of their proposals, Timelock. A probabilistic analysis and real attack experiment reveal that the security level guaranteed by Timelock is lower than that claimed in Bianchi et al.’s paper. As countermeasures to this problem, three PIN-entry methods are proposed and a usability study is performed. According to the result of this study, a simple modification may improve the security significantly while retaining the design philosophy of unimodal systems. In addition, the proposed methods address the PIN compatibility issue of Timelock and they can be used to enter a legacy numerical PIN without any change in the PIN

A Semi‐Crystalline Polymer Semiconductor with Thin Film Stretchability Exceeding 200%

Abstract Despite the emerging scientific interest in polymer‐based stretchable electronics, the trade‐off between the crystallinity and stretchability of intrinsically stretchable polymer semiconductors—charge‐carrier mobility increases as crystallinity increases while stretchability decreases—hinders the development of high‐performance stretchable electronics. Herein, a highly stretchable polymer semiconductor is reported that shows concurrently improved thin film crystallinity and stretchability upon thermal annealing. The polymer thin films annealed at temperatures higher than their crystallization temperatures exhibit substantially improved thin film stretchability (> 200%) and hole mobility (≥ 0.2 cm2 V−1 s−1). The simultaneous enhancement of the crystallinity and stretchability is attributed to the thermally‐assisted structural phase transition that allows the formation of edge‐on crystallites and reinforces interchain noncovalent interactions. These results provide new insights into how the current crystallinity–stretchability limitation can be overcome. Furthermore, the results will facilitate the design of high‐mobility stretchable polymer semiconductors for high‐performance stretchable electronics

Effects of the Anode Diffusion Layer on the Performance of a Nonenzymatic Electrochemical Glucose Fuel Cell with a Proton Exchange Membrane.

It is necessary to apply a nonenzymatic glucose fuel cell using a proton exchange membrane for an implantable biomedical device that operates at low power. The permeability of glucose with high viscosity and a large molecular weight in the porous medium of the diffusion layer was investigated for use in fuel cells. Carbon paper was prepared as an anode diffusion layer, and it was analyzed with a diffusion layer treated with polytetrafluoroethylene (PTFE) and a microporous layer (MPL). When untreated carbon paper was applied, the peak power density (PPD) and open-circuit voltage (OCV) increased as the glucose concentration and flow rate increased. On this occasion, the highest PPD of 17.81 μW cm-2 was achieved at 3 mM and a 2.0 mL min-1 glucose aqueous solution (at atmospheric pressure and 36.5 °C). The diffusion layer, which became more hydrophobic through PTFE treatment, adversely affected glucose permeability. In addition, the addition of an MPL decreased OCV and PPD with increasing glucose concentrations and flow rates. Compared with untreated carbon paper, the PPD was six times lower approximately. Consequently, it was confirmed that the properties of carbon paper, such as low hydrophobicity, high porosity, and thin thickness, would be advantageous for nonenzymatic glucose fuel cells

Thermally Stable and High???Mobility Dithienopyran???Based Copolymers: How Donor???Acceptor??? and Donor???Donor???Type Structures Differ in Thin???Film Transistors

Although rapid and remarkable progress has been made in semiconducting polymers used in organic field-effect transistors (OFETs), the development of novel ??-conjugated backbones remains the central issue in this field. High FET mobilities have been achieved for copolymers based on fused-ring building blocks due to their strong tendency to form ??????? stacks. However, introducing the recently formulated strong electron-rich fused-ring dithienopyran (DTP) unit in the polymer backbone has garnered considerably less attention. Herein, four new copolymers (donor???acceptor (D???A)-type versus donor???donor (D???D)-type structures) are synthesized based on the DTP unit by adopting different types of counterparts of the backbone. The characteristics of these copolymers, derived from different structural types, are investigated and compared and they are implemented in OFET devices. The D???A-type copolymers (P1 and P2) show higher charge-carrier mobilities and better thermal stability than the D???D-type copolymers (P3 and P4), attributed to enhanced crystalline features induced by strong intermolecular interactions and preferential 3D-textured molecular orientation of the D???A-type copolymers. Particularly, P1 exhibits the highest mobility of up to 0.22???cm2???V???1???s???1. This study provides a reference for understanding the influence of the backbone type on the structure???property relation and promotes the development of high-performance DTP-based copolymers

Fe-doped tricalcium phosphates: crystal structure and degradation behavior

β -tricalcium phosphate ( β -TCP, Ca3(PO4)2) is biodegradable ceramics with chemical and mineral compositions similar to those of bone. It is a potential candidate for bone repair surgery, and substituting the Fe ions can improve its biological behavior. In this study, we investigated the effect of Fe ions on the structural deviation and in vitro behavior of β -TCP. Fe-doped β -TCP were synthesized by the co-precipitation method, and the heat treatment temperature was set at 1100 °C. The chemical state of the Fe-doped β -TCP was analyzed by x-ray photoelectron spectroscopy, while structural analysis was carried out by Rietveld refinement using the x-ray diffraction results. Fe ions existed in both Fe ^2+ and Fe ^3+ states and occupied the Ca-(4) and Ca-(5) sites. Fe ions enhanced the degradation of β -TCP and resorption behavior onto the surface of β -TCP during the immersion test. As a result, Fe ion improves the initial cell adhesion and proliferation behavior of β -TCP

Photothermally Triggered Fast Responding Hydrogels Incorporating a Hydrophobic Moiety for Light-Controlled Microvalves

Iron oxide nanoparticles dispersed within a thermally responsive poly­(<i>N</i>-isopropylacrylamide) (PNIPAm) hydrogel matrix effectively convert the photo energy of visible light of modest intensity into thermal energy, providing the efficient means to trigger changes in volumetric swelling of hydrogels. However, long irradiation time (on the order of minutes) and modest volume change limit their applications that need fast response and/or large volume change. In this work, we found that the degree of volume change triggered by light could be maximized by adjusting the lower critical solution temperature (LCST) of the hydrogels. On the basis of the evidence in this investigation, we can develop highly responsive hydrogels that show rapid and significant light-induced volume change, which could be achieved by incorporating a hydrophobic <i>N</i>,<i>N</i>-diethylacrylamide moiety in the PNIPAm network. This enhanced responsiveness led to the successful application of this material in a remote-controllable microvalve for microfluidic devices operated by light illumination within a few seconds

Non-Dimensional Analysis of Diffusion Characteristics in Polymer Electrolyte Membrane Fuel Cells with Mismatched Anodic and Cathodic Flow Channels

Polymer electrolyte membrane fuel cells were analyzed to investigate changes in the structure of the flow field and operating conditions. The cell performance, which was controlled by adjusting the width of the cathodic channel, improved as the backpressure increases. With the anodic and cathodic flow channels mismatched, the maximum power densities at 3.0 bar for a narrow cathodic channel were 1115 and 1024 mW/cm2, and those for a wide cathodic channel were 959 and 868 mW/cm2, respectively. The diffusion characteristics were investigated using the non-dimensional numbers Re (Reynolds), Sc (Schmidt), and Sh (Sherwood) to confirm the improvement of mass transport. The narrower the channel or the higher the operating pressure, the larger Re was and the smaller Sc and Sh became. In particular, the wider the anodic channel, the larger the value of Sh

Kruppel-like factor KLF8 plays a critical role in adipocyte differentiation.

KLF8 (Krüppel-like factor 8) is a zinc-finger transcription factor known to play an essential role in the regulation of the cell cycle, apoptosis, and differentiation. However, its physiological roles and functions in adipogenesis remain unclear. In the present study, we show that KLF8 acts as a key regulator controlling adipocyte differentiation. In 3T3-L1 preadipocytes, we found that KLF8 expression was induced during differentiation, which was followed by expression of peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT/enhancer-binding protein α (C/EBPα). Adipocyte differentiation was significantly attenuated by the addition of siRNA against KLF8, whereas overexpression of KLF8 resulted in enhanced differentiation. Furthermore, luciferase reporter assays demonstrated that overexpression of KLF8 induced PPARγ2 and C/EBPα promoter activity, suggesting that KLF8 is an upstream regulator of PPARγ and C/EBPα. The KLF8 binding sites were localized by site mutation analysis to -191 region in C/EBPα promoter and -303 region in PPARγ promoter, respectively. Taken together, these data reveal that KLF8 is a key component of the transcription factor network that controls terminal differentiation during adipogenesis

Non-Dimensional Analysis of Diffusion Characteristics in Polymer Electrolyte Membrane Fuel Cells with Mismatched Anodic and Cathodic Flow Channels

Polymer electrolyte membrane fuel cells were analyzed to investigate changes in the structure of the flow field and operating conditions. The cell performance, which was controlled by adjusting the width of the cathodic channel, improved as the backpressure increases. With the anodic and cathodic flow channels mismatched, the maximum power densities at 3.0 bar for a narrow cathodic channel were 1115 and 1024 mW/cm2, and those for a wide cathodic channel were 959 and 868 mW/cm2, respectively. The diffusion characteristics were investigated using the non-dimensional numbers Re (Reynolds), Sc (Schmidt), and Sh (Sherwood) to confirm the improvement of mass transport. The narrower the channel or the higher the operating pressure, the larger Re was and the smaller Sc and Sh became. In particular, the wider the anodic channel, the larger the value of Sh

Utilizing a Siloxane-Modified Organic Semiconductor for Photoelectrochemical Water Splitting

Weexplore the potential of employing diketopyrrolopyrrole (DPP)based pi-conjugated OSs as a hole transport layer material inheteroatom-doped hematite (Ti-Fe2O3/Ge-Fe2O3) photoanodes for efficient photoelectrochemicalwater splitting. The siloxane-modified pi-conjugated polymer(P-Si) with a high carrier mobility and crystallinity revealedgreat potential to extract holes by forming a built-in potential withhematite photoanodes while showing high stability in an alkaline electrolytefor photoelectrochemical water oxidation. Because of the easy holeextraction and subsequent fast hole transport property of the P-Si interlayer between NiFe-(OH)( x ) and Ge-doped porous Fe2O3(Ge-PH), NiFe-(OH)( x )/P-Si/Ge-PH showed a 1.8-fold increasein photocurrent density (4.57 mA cm(-2) at 1.23 V-RHE) with a cathodic shift of the onset potential (0.735 V-RHE) and good stability for 65 h compared to Ge-PH. This studydemonstrates the successful use of inherently unstable pi-conjugatedOSs as a hole extracting/transport medium in a photoanode, addressingthe intrinsic recombination issues of hematite for efficient and stablewater splitting