Table of Contents:Mazzeo et al. describe methods of patterning metallized paper to create touch pads of arrayed buttons that are sensitive to contact with both bare and gloved fingers. The paper-based keypad shown detects the change in capacitance associated with the touch of a finger to one of its buttons. Mounted to an alarmed cardboard box, the keypad requires the appropriate sequence of touches to disarm the system. Image for Table of Contents:Submitted to 2 This paper describes low-cost, thin, and pliable touch pads constructed from a commercially available, metallized paper commonly used as packaging material for beverages and book covers. The individual keys in the touch pads detect changes in capacitance or contact with fingers by using the effective capacitance of the human body and the electrical impedance across the tip of a finger. To create the individual keys, a laser cutter ablates lines through the film of evaporated aluminum on the metallized paper to pattern distinct, conductive regions. This work includes the experimental characterization of two types of capacitive buttons and illustrates their use with applications in a keypad with 10 individually addressable keys, a keypad that conforms to a cube, and a keypad on an alarmed cardboard box. With their easily arrayed keys, environmentally benign material, and low cost, the touch pads have the potential to contribute to future developments in disposable, flexible electronics, active, "smart" packaging, user interfaces for biomedical instrumentation, biomedical devices for the developing world, applications for monitoring animal and plant health, food and water quality, and disposable games (e.g., providers of content for consumer products).There is no simple method of integrating buttons with structures on single-use or throwaway devices. Current commercial buttons are not thin enough, inexpensive enough, or easy enough to array seamlessly with paper-based products for disposable applications. The touch pads in this work are thin (~60 µm in some cases), simple to array, fabricated by etching patterns into metallized paper, low-cost (< $0.25 m -2 for the thin grade of metallized paper we use in this work), and lightweight (100s of g m -2 ). The individual keys measure changes in capacitance when touched by a user, and the buttons require no physical displacement of conductive elements. Even though the individual keys on the touch pads detect changes in capacitance, the paper-based keypads are still functional when touched by fingers in nitrile gloves. Submitted to 3Developments in paper-based electronics include ring oscillators with organic electronics [1] , transistors [2][3][4] , methods for patterning conductive traces [5][6][7] , speakers [8] , super capacitors [9] , batteries [10] , MEMS [11] , and solar cells [12] . Each of these developments focuses on a single technological advance that would enable new types of consumer products. Many types of new consumer products will require some form of user interface or input. In order to gather ke...

Ionic mass transport including electrolyte diffusivity and conductivity depends on the geometric tortuosity of the electrode. This paper compares two experimental methods that determine tortuosity based on diffusivity or conductivity. The polarization-interrupt method previously developed by our group determines tortuosity in terms of effective diffusivity. The blocking-electrolyte method proposed by Gasteiger and coworkers determines tortuosity in terms of effective ionic conductivity and is analyzed using a generalized transmission-line model to account for multiple sources of impedance. Tortuosity of several commercial-quality electrodes was measured using both methods, producing reasonable agreement between the two methods in most cases. The advantages and disadvantages of each method and variables that can affect the accuracy of the measurement, such as electrode wetting and model fitting, are discussed. For particular electrodes, one method may be advantageous or more conveniently applied than the other.

The fabrication process of Li-ion battery electrodes plays a prominent role in the microstructure and corresponding cell performance. Here, a mesoscale particle dynamics simulation is developed to relate the manufacturing process of a cathode containing Toda NCM-523 active material to physical and structural properties of the dried film. Particle interactions are simulated with shifted-force Lennard-Jones and granular Hertzian functions. LAMMPS, a freely available particle simulator, is used to generate particle trajectories and resulting predicted properties. To make simulations of the full film thickness feasible, the carbon binder domain (CBD) is approximated with μm-scale particles, each representing about 1000 carbon black particles and associated binder. Metrics for model parameterization and validation are measured experimentally and include the following: slurry viscosity, elasticity of the dried film, shrinkage ratio during drying, volume fraction of phases, slurry and dried film densities, and microstructure cross sections. Simulation results are in substantial agreement with experiment, showing that the simulations reasonably reproduce the relevant physics of particle arrangement during fabrication.

Local variations of mechanical, structural, transport, and kinetic properties, referred to as heterogeneity can detrimentally affect battery life and performance. Local heterogeneity results in non-uniform current, temperature, state of charge (SOC), and aging. In this work, we introduce a model that combines Newman-type and equivalent circuit submodels to further understand and quantify the effects of electrode inhomogeneities. For modeling purposes, three regions of different microstructural properties are connected in parallel, to represent measured electrode heterogeneity. Multiple cases of heterogeneities, such as non-uniform ionic resistance and active material loading, are studied at different rates of discharge and charge. The results show that higher rates increase non-uniformities of dependent properties such as temperature, current density, positive and negative electrode states of charge, and charge and discharge capacities, especially in the case of charging. In addition, by calculating the overpotential on the negative electrode, it is shown that lithium could plate non-uniformly on the negative electrode during high rates of charge. Finally, a sensitivity analysis is performed to understand the significance of heterogeneity on different properties.

Electronic conductivity of battery electrodes and the interfacial resistance at the current collector are key metrics affecting cell performance. However, in many cases they have not been properly quantified because of the lack of a suitably accurate and convenient non-destructive measurement method. There are also indications that conductivity across deposited films is not uniformly distributed. To characterize these variations, a micro-four-line probe has been developed for local mesoscale measurement of electronic conductivity of thin-film electrodes. The micro-four-line probe, coupled with a previously discussed mathematical model, overcomes key limitations of traditional point probes. This new approach allows pressure-controlled surface measurements to determine electronic conductivity without removal of the current collector. In addition, the probe allows one to measure the local interfacial contact resistance between the electrode film and the current collector. The method was validated by comparing to other conductivity sampling methods for a conductive test film. Three commercial-quality Li-ion battery porous electrodes were also tested and conductivity maps were produced. The results show significant local conductivity variation in such electrodes on a millimeter length scale. This method is of value to battery manufacturers and researchers to better quantify sources of resistance and heterogeneity and to improve electrode quality. A common electrode design for secondary batteries is a porous thin film of active material particles, conductive carbon particles, and polymeric binder. The film is coated on a metallic current collector. For commercially produced cells based on lithium-ion intercalation chemistry, the active materials are commonly a transition metal oxide on aluminum for the cathode and graphite on copper for the anode.Among the key properties determining electrode performance are the volume-averaged (effective or bulk) electronic conductivity of the film and the interfacial resistance at the current collector.1-4 These two quantities are surprisingly difficult to measure accurately for common thin-film electrodes because of the relatively large contact resistance between the sample and external probes, mechanical fragility of the sample, and the presence of the attached current collector. Lack of experimental data makes it hard to meet a longstanding need to be able to predict these parameters from knowledge of the composition and structure of the constituent materials.Commercial Li-ion battery electrodes are fabricated by first by making a slurry of the active material, carbon additive, binder, and a carrier solvent. This slurry is spread onto a metal foil current collector in a continuous process using a blade or slit to control deposition thickness, and then is immediately dried. Even in commercial coating processes it is difficult to achieve a uniform distribution of particles and porosity, leading to variability in the electronic conductivity of the electrodes.5 While this variability...

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Heterogeneity of porous electrodes can cause battery failure and performance deficiencies. On the other hand, some types of heterogeneity can improve performance. This study uses a multi-phase smoothed particle (MPSP) model, derived from smoothed particle hydrodynamics (SPH) and which is parameterized and validated by comparison with experimental viscosity, density, electronic conductivity, MacMullin number, and Young’s modulus of electrode films. The MPSP model simulates all major aspects of electrode production: mixing, coating, drying, and calendering, though the focus in this paper (Part 1) is on drying and calendering. Four types of electrodes are included in this study: a graphite anode and three traditional metal oxide cathodes. The model suggests how some types of heterogeneity can form during cathode and anode fabrication. The anode is more susceptible to mesoscale heterogeneities than the cathode due to differences in active particle shape and stiffness. The model and experiments show that regardless of the active material type, calendering increases the variability in electronic and ionic conductivity due to carbon and binder redistribution. This can be explained by means of the proposed multi-phase packing theory. On the other hand, calendering increases mechanical uniformity as also shown by model and experiment.

Protein charge organization is dependent on the low-permittivity region in the hydrophobic core of the molecule. We suggest a novel approach to estimate the dielectric constant of this region by comparing measured and simulated first- and second-order charge moments. Here, the dipole moment is measured as a function of pH using dielectric spectroscopy. The results are compared to dipole moments based on Poisson-Boltzmann estimates of pK(a) shifts calculated from structures in the Protein Data Bank. Structures are additionally refined using CHARMM molecular dynamics simulations. The best estimate for the internal permittivity is found by minimizing the root-mean-square residual between measured and predicted charge moments. Using the protein β-lactoglobulin, a core dielectric constant in the range of 6-7 is estimated.