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...
This paper describes the design and fabrication of electrically controlled paper actuators that operate based on the dimensional changes of that occur in paper when the moisture absorbed on the surface of the cellulose fibers changes. These actuators are called "Hygroexpansive Electrothermal Paper Actuators" (HEPAs). The actuators are made from paper, conducting polymer, and adhesive tape. They are lightweight, inexpensive, and can be fabricated using simple printing techniques. The central element of the HEPAs is a porous conducting path (used to provide electrothermal heating) that changes the moisture content of the paper and causes actuation. This conducting path is made by embedding a conducting polymer (PEDOT:PSS) within the paper, and thus making a paper / polymer composite that retains the porosity and hydrophilicity of paper. Different types of HEPAs (straight, pre-curved, and creased) achieved different types of motions (e.g., bending motion, accordion type motion). A theoretical model for their behavior is proposed. These actuators have been used for the manipulation of liquids, and for the fabrication of an optical shutter.
More detailed details on the dimensions of the dies, additional devices and videos of the running experiments are available in the supporting information.
International audienceChemical grafting has been widely used to modify the surface properties of materials, especially surface energy for controlled wetting, because of the resilience of such coatings/modifications. Reagents with multiple reactive sites have been used with the expectation that a monolayer will form. The step-growth polymerization mechanism, however, suggests the possibility of gel formation for hydrolyzable moieties in the presence of physisorbed water. In this report, we demonstrated that using alkyltrichlorosilanes (trivalent [i.e., 3 reactive sites]) in the surface modification of a cellulosic material (paper) does not yield a monolayer but rather gives surface-bound particles. We infer that the presence of physisorbed (surface-bound) water allows for polymerization (or oligomerization) of the silane prior to its attachment on the surface. Surface energy mismatch between the hydrophobic tails of the growing polymer and any unreacted bound water leads to the assembly of the polymerizing material into spherical particles to minimize surface tension. By varying paper grammage (16.2–201.4 g m À2), we varied the accessible surface area and thus the amount of surface-adsorbed water, allowing us to control the ratio of the silane to the bound water. Using this approach, polymeric particles were formed on the surface of cellulose fibers ranging from $70 nm to a film. The hydrophobicity of the surface, as determined by water contact angles, correlates with particle sizes (p < 0.001, Student's t-test), and, hence, the hydrophobicity can be tuned (contact angle between 94 and 149). Using a model structure of a house, we demonstrated that as a result of this modification, paper-based houses can be rendered self-cleaning or tolerant to surface running water. In another application, we demonstrated that the felicitous choice of architectural design allows for the hydrophobic paper to be used for water harvesting
It is nearly impossible to separate two interleaved phonebooks when held by their spines. A full understanding of this astonishing demonstration of solid friction in complex assemblies has remained elusive. In this Letter, we report on experiments with controlled booklets and show that the force required increases sharply with the number of sheets. A model captures the effect of the number of sheets, their thickness and the overlapping distance. Furthermore, the data collapse onto a selfsimilar master curve with one dimensionless amplification parameter. In addition to solving a longstanding familiar enigma, this model system provides a framework with which one can accurately measure friction forces and coefficients at low loads, and that has relevance to complex assemblies from the macro to the nanoscale.Many of us are familiar with a classical demonstration of the strength of friction: take two phonebooks, interleave their sheets and try to separate them by pulling on their spines. This demonstration has been carried out spectacularly by attempting to pull the books apart with people, trucks, lifting a car [1], and even two military tanks [2], only to fail and suggest that the inner friction between these sheets prevails. The simple explanation often given is that gravity provides the normal force that generates the tangential friction, but this hypothesis is easily proven to be wrong as there is no discernible difference between such an experiment carried out in the vertical or horizontal direction. In this Letter, we study the force needed to separate two books as a function of the number of sheets, the thickness of the sheets, and the interleaving distance. In particular, we show that the force required to separate the books increases abruptly with the number of sheets. The strength of the system is due to the operator: the person, car, truck, or tank, amplifies any small friction arising from the normal force acting on the boundaries of the stack. We present a simple model that captures all the data into a self-similar master curve. The model depends on one single dimensionless amplification parameter, and thus gives insight into the mechanisms at play in this deceivingly complex system. In addition to solving a long-standing familiar enigma related to the classical problem of friction, this model system provides a framework within which one can accurately measure friction forces and coefficients at low loads, and opens the way to the technologically-relevant engineering of friction in complex assemblies from the macro to the nanoscale.The first-known systematic studies of friction were carried out five centuries ago by da Vinci [3, 4] who discov- * frederic.restagno@u-psud.fr ered basic rules which were later confirmed by Amontons [3]. In particular, these laws establish that the friction force is independent of the contact area and proportional to the applied load during sliding, the proportionality constant being the coefficient of kinetic friction. Coulomb rediscovered these laws and further determined...
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