Revealable Functional Commitments: How to Partially Reveal a Secret Function

A revealable functional commitment allows a prover to commit to a secret polynomial size function $f$. Later, the prover has the ability to (1) prove that $y = f(x)$ for public $x, y$ and (2) open a small window into $f$\u27s machinery, via an encoded set of constraints - all without divulging any other information about $f$. In this way, revealable functional commitments allow the operator of a proprietary function to prove desired predicate about the function. For example, a government can commit to a bail decision algorithm, and prove that the same algorithm is being used for all defendants. They can also quell concerns about bias, and increase transparency processes by revealing windows into what their function does - while keeping most of their function secret to prevent exploitation. To build a revealable functional commitment, we introduce a \u27proof of reveal\u27, to show that a set of constraints, combined with a set of guarantees about those constraints, is consistent with a committed secret function. We show that combining a algebraic holomorphic proof (AHP), a \u27proof of function relation\u27 (PFR), and a proof of reveal yields a secure revealable functional commitment scheme. Additionally, we construct proof of reveals for two popular PFR-equipped AHPs, and obtain two instantiations of revealable functional commitments. Towards that end, we also develop interactive protocols that prove properties of committed polynomials, which may have independent value

The Mechanical Properties of Individual, Electrospun Fibrinogen Fibers

We used a combined atomic force microscope (AFM)/fluorescence microscope technique to study the mechanical properties of individual, electrospun fibrinogen fibers in aqueous buffer. Fibers (average diameter 208 nm) were suspended over 12 μm-wide grooves in a striated, transparent substrate. The AFM, situated above the sample, was used to laterally stretch the fibers and to measure the applied force. The fluorescence microscope, situated below the sample, was used to visualize the stretching process. The fibers could be stretched to 2.3 times their original length before breaking; the breaking stress was 22·106 Pa. We collected incremental stress-strain curves to determine the viscoelastic behavior of these fibers. The total stretch modulus was 16·106 Pa and the relaxed, elastic modulus was 6.7·106 Pa. When held at constant strain, electrospun fibrinogen fibers showed a fast and slow stress relaxation time of 3 and 56 seconds. Our fibers were spun from the typically used 90% 1,1,1,3,3,3-hexafluoro-2-propanol (90-HFP) electrospinning solution and resuspended in aqueous buffer. Circular dichroism spectra indicate that alpha-helical content of fibrinogen is ~70% higher in 90-HFP than in aqueous solution. These data are needed to understand the mechanical behavior of electrospun fibrinogen structures. Our technique is also applicable to study other, nanoscopic fibers

Efficient organic-inorganic hybrid perovskite solar cells processed in air

Organic-inorganic hybrid perovskite solar cells with fluorine doped tin oxide/titanium dioxide/CH3NH3PbI3-xClx/poly(3-hexylthiophene)/silver were made in air with more than 50% humidity. The best devices showed an open circuit voltage of 640 mV, a short circuit current density of 18.85 mA cm-2, a fill factor of 0.407 and a power conversion efficiency of 5.67%. The devices showed external quantum efficiency varying from 60 to 80% over a wavelength region of 350 nm to 750 nm of the solar spectrum. The morphology of the perovskite was investigated using scanning electron microscopy and it was found to be porous in nature. This study provides insights into air-stability of perovskite solar cells

High performance, transparent solution-processed organic field effect transistor with low-k elastomeric gate dielectric and liquid crystalline semiconductor: Promises and Challenges

The highly flexible and stretchable polymer elastomer having a low dielectric constant (k~ 2.6), called poly(dimethylsiloxane) (PDMS), is a promising gate dielectric material for solution-processed organic field effect transistors (OFETs). A detailed understanding of PDMS based OFETs is required to extend its application to flexible electronic devices. The present work discusses about the promises and challenges of PDMS based solution-processed OFETs using a liquid crystal (LC), 2-decyl-7-phenyl-benzothienobenzothiophene (Ph-BTBT-10) as semiconducting channel material. The liquid crystal-OFET (LC-OFET) exhibits high electrical performance such as high hole mobility of ~ 22 cm2V-1s-1, low threshold voltage ( 90 %). The electrical performance of LC-OFETs are observed to have a significant correlation with the annealing temperature of Ph-BTBT-10 layer and is also influenced by the different operating conditions such as air, nitrogen and vacuum. The OFETs demonstrate anomalous bias stress behavior and hysteresis which are also addressed

Surface-Treated Poly(dimethylsiloxane) as a Gate Dielectric in Solution-Processed Organic Field-Effect Transistors

Poly­(dimethylsiloxane) (PDMS) is a transparent and flexible elastomer which has a myriad of applications in various fields including organic electronics. However, the inherent hydrophobic nature and low surface energy of PDMS prevent its direct use in many applications. It is seldom utilized as a gate dielectric in solution-processed organic field effect transistors (OFETs). In this work, we demonstrate a simple method, extended ultraviolet–ozone (UVO) treatment, to modify the PDMS surface and effectively employ it in solution-processed OFETs as a gate dielectric material. The modified PDMS surface shows enhanced wettability and adherence to both polar and nonpolar liquids, which is contrary to the generally observed hydrophilic nature of UVO-treated PDMS surfaces because of the creation of polar functional groups. The morphological changes happening on the PDMS surface as a result of extended UVO treatment play a major role in making the surface suitable for all type of solvents discussed here. The contact angle measurements are used to give qualitative evidence for this observation. The modified PDMS is then used as a gate dielectric in solution-processed n- and p-channel OFETs using [6,6]-phenyl-C61-butyric acid methyl ester (PC₆₀BM) and regioregular poly­(3-hexylthiophene) (rr-P3HT) semiconductors, respectively

Fabrication of a novel biomaterial with enhanced mechanical and conducting properties

Conducting polymers have the combined advantages of metal conductivity with ease in processing and biocompatibility; making them extremely versatile for biosensor and tissue engineering applications. However, the inherent brittle property of conducting polymers limits their direct use in such applications which generally warrant soft and flexible material responses. Addition of fillers increases the material compliance, but is achieved at the cost of reduced electrical conductivity. To retain suitable conductivity without compromising the mechanical properties, we fabricate an electroactive blend (dPEDOT) using low grade PEDOT: PSS as the base conducting polymer with polyvinyl alcohol as filler and glycerol as a dopant. Bulk dPEDOT films show a thermally stable response till 110 degrees C with over seven fold increase in room temperature conductivity as compared to 0.002 S cm(-1) for pristine PEDOT: PSS. We characterize the nonlinear stress-strain response of dPEDOT, well described using a Mooney-Rivlin hyperelastic model, and report elastomer-like moduli with ductility similar to fives times its original length. Dynamic mechanical analysis shows constant storage moduli over a large range of frequencies with corresponding linear increase in tan(delta). We relate the enhanced performance of dPEDOT with the underlying structural constituents using FTIR and AFM microscopy. These data demonstrate specific interactions between individual components of dPEDOT, and their effect on surface topography and material properties. Finally, we show biocompatibility of dPEDOT using fibroblasts that have comparable cell morphologies and viability as the control, which make dPEDOT attractive as a biomaterial

Efficient Organic Photovoltaics with Improved Charge Extraction and High Short-Circuit Current

Exciton generation, dissociation, free carrier transport, and charge extraction play an important role in the short-circuit current (J(sc)) and power conversion efficiency of an organic bulk heterojunction (BHJ) solar cell (SC). Here we study the impact of band offset at the interfacial layer and the morphology of active layer on the extraction of free carriers. The effects are evaluated on an inverted BHJ SC using zinc oxide (ZnO) as a buffer layer, prepared via two different methods: ZnO nanoparticle dispersed in mixed solvents (ZnO A) and sol-gel method (ZnO B). The device with ZnO A buffer layer improves the charge extraction and J(sc),. The improvement is due to the better band offset and morphology of the blend near the ZnO A/active layer interface. Further, the numerical analysis of current-voltage characteristics illustrates that the morphology at the ZnO A/active layer interface has a more dominant role in improving the performance of the organic photovoltaic than the band offset