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Emerging applications of the Internet of Things in healthcare, wellness, and gaming require continuous monitoring of the body and its environment, fueling the need for wearable devices able to maintain intimate, reliable, and unobtrusive contact with the human body. This translates in the necessity to develop soft and deformable electronics that match the body's mechanics and dynamics. In recent years, various strategies have been proposed to form stretchable circuits and more specifically elastic electrical conductors embedded in elastomeric substrate using either geometrical structuring of solid conductors or intrinsically stretchable materials. Gallium (Ga)-based liquid metals (LMs) are an emerging class of materials offering a particularly interesting set of properties for the design of intrinsically deformable conductors. They concomitantly offer the high electrical conductivity of metals with the ability of liquids to flow and reconfigure. The specific chemical and physical properties of Ga-based LMs differ fundamentally from those of solid conductors and need to be considered to successfully process and implement them into stretchable electronic devices. In this Account, we report on how the key physical and chemical properties of Ga-based LMs can be leveraged to enable repeatable manufacturing and precise patterning of stretchable LM conductors. A comprehensive understanding of the interplay between the LM, its receiving substrate chemistry and topography, and the environmental conditions is necessary to meet the reproducibility and reliability standards for large scale deployment in next-generation wearable systems. In oxidative environments, a solid oxide skin forms at the surface of the LM and provides enough stiffness to counterbalance surface tension, and prevent the LM from beading up to a spherical shape. We review techniques that advantageously harness the oxide skin to form metastable structures such as spraying, 3D printing, or channel injection. Next, we explore how controlling the environmental condition prevents the formation or removes the oxide skin, thereby allowing for selective wetting of Ga lyophilic surfaces. Representative examples include selective plating and physical vapor deposition. The wettability of LMs can be further tuned by engineering the surface chemistry and topology of the receiving substrate to form superlyophobic or superlyophilic surfaces. In particular, our group developed Ga-superlyophilic substrates by engineering the surface of silicone rubber with microstructures and a gold coating layer. Thermal evaporation of Ga on such engineered substrates allows for the formation of smooth LM films with micrometric thickness control and design freedom. The versatility of the available deposition techniques facilitates the implementation of LM conductors in a wide variety of wearable devices. We review various epidermal electronic systems using LM conductors as interconnects to carry power and information, transducers and sensors, antennas, and complex hybrid (soft-rigid) electronic circuits. In addition, we highlight the limitations and challenges inherent to the use of Ga LM conductors that include electromigration, corrosion, solidification, and biocompatibility.

Stretchable biphasic conductors are formed by physical vapor deposition of gallium onto an alloying metal film. The properties of the photolithography-compatible thin metal films are highlighted by low sheet resistance (0.5 Ω sq(-1) ) and large stretchability (400%). This novel approach to deposit and pattern liquid metals enables extremely robust, multilayer and soft circuits, sensors, and actuators.

Mechanically soft neural implants When implanting a material into the body, not only does it need the right functional properties, but it also needs to have mechanical properties that match the native tissue or organ. If the material is too soft, it will be mechanically degraded, and if it is too hard it may get covered with scar tissue or it may damage the surrounding tissues. Starting with a transparent silicone substrate, Minev et al. patterned microfluidic channels to allow for drug delivery, and soft platinum/silicone electrodes and stretchable gold interconnects for transmitting electrical excitations and transferring electrophysiological signals. In tests of spinal cord implants, the soft neural implants showed biointegration and functionality within the central nervous system. Science , this issue p. 159

On page 4507, S. P. Lacour and co-workers present highly conductive and stretchable solid-liquid films that are formed by physical vapor deposition of gallium onto an alloying gold layer. The image shows patterns defined by lift-off on an elastomer membrane. The magnified view is a false-color scanning electron microscopy (SEM) image (×5000) of the surface of the films under 50% applied strain, showing the liquid Ga (blue-gray) flowing between the AuGa2 /Ga clusters (gold).

In article number https://doi.org/10.1002/advs.201800256, Arthur Hirsch and Stéphanie P. Lacour engineer the surface chemistry and topography of silicone rubber (PDMS) with micro‐structured pillars and a gold pre‐coating layer to produce gallium super‐lyophilic substrates. Physical vapor deposition of gallium leads to the formation of smooth and homogeneous films by imbibition of the surface topography rather than coalescence and formation of gallium drops. By capillarity, gallium accumulates in between the pillars up to their top surface, forming a smooth film.

International audience; Electrical neuromodulation of lumbar segments improves motor control after spinal cord injury in animal models and humans. However, the physiological principles underlying the effect of this intervention remain poorly understood, which has limited the therapeutic approach to continuous stimulation applied to restricted spinal cord locations. Here we developed stimulation protocols that reproduce the natural dynamics of motoneuron activation during locomotion. For this, we computed the spatiotemporal activation pattern of muscle synergies during locomotion in healthy rats. Computer simulations identified optimal electrode locations to target each synergy through the recruitment of proprioceptive feedback circuits. This framework steered the design of spatially selective spinal implants and real-time control software that modulate extensor and flexor synergies with precise temporal resolution. Spatiotemporal neuromodulation therapies improved gait quality, weight-bearing capacity, endurance and skilled locomotion in several rodent models of spinal cord injury. These new concepts are directly translatable to strategies to improve motor control in humans.

A 29: There are several hundred types of cheeses on the market. This discussion will be limited to hard cheeses. For clarification, soft cheese examples are cottage, cream, and farmer cheeses. The hard cheeses include: swiss, munster, american, gouda, etc.

A 20: The computer age has overtaken the packaging industry. Those who failed to recognize the many facets of computer control and utilize them to advantage have been left behind to suffer the fate of the quill pen. The modern business relies on computer assistance in all its operations. The computer has offered these advantages: a. Faster decision making b. Speedier problem solving c. Quality improvement d. Higher yields e. Bottleneck elimination f. Inventory reduction

A 21: In addition to all the problems present in ordinary food packaging, there are several exclusively related to frozen food. Low temperature (about 10-20°F) retards bacterial degradation. Under these circumstances the packaging material is not called upon to furnish the type of protection required for refrigerated foods. The primary function of the package is thus relegated to “contain” and “display.” The package may be as simple as a polyethylene bag or a waxed box. These materials provide the primary protection required—moisture barrier. The atmosphere in the freezer case is relatively dry. Products placed in this environment are in danger of drying out—freezer burn. Packaging materials with good MVTR are thus required to overcome the moisture loss tendency. Polyolefins and waxes are prime contenders for this service.

A 18: It should be remembered that all packaging involves compromises. Since there are many aspects to the selection of a package—it is almost impossible to achieve a perfect combination of properties. Our answer will be restricted to protection, display, and utility.

A 32: The terms “tamperproof” or “tamper resistant” are incorrect. Some of the most sophisticated security systems have been unable to keep burglars from tampering with safes or otherwise secured premises. The best we can hope for is a “tamper evident” closure. Certainly, a package which may travel for hundreds or even thousands of miles from its point of manufacture to its sale to a consumer—this same package, which will have spent days on an open shelf, will have offered many opportunities to a tamperer to invade the package. We know for certain that many packages are smuggled out of the retail establishment to avoid payment for the product. It is also well known that many cases of product disappear in shipment. One accepts this pilferage as the cost of doing business. The consumer of course pays for the stolen items in increased product cost.

A 6: Currently, a range of barrier materials are available. Selection of the best product for a given application requires careful consideration of many factors. Foils provide excellent barrier, but preclude product visibility. The products discussed herein offer see-through properties at somewhat reduced shelf life.

A 11: Aseptic means free of pathogenic microorganisms. It is desirable to package food with as low a bacterial population as is feasible. In addition we attempt to retard the further growth of microbes by refrigeration, controlled atmosphere, or freezing. Another approach to food preservation depends on post packaging thermal treatment to reduce the microbial count. A brief heat treatment (30 minutes at 143°F or 15 sec at 160°F), known as pasteurization, kills most but not all pathogenic microbes. The product thus treated can be retained under refrigeration for several days. A much more severe heat process (15 minutes at 250 °F) will achieve a bacteria free product which can be stored at room temperature for months or even years.

A 3: The question is not which one of these types is better but rather which one is better suited for a given packaging assignment. Both vacuum and gas packaging do provide a means for increasing the shelf life of the packaged product. The vacuum package affords protection through removal of most of the oxygen surrounding the product. It is erroneous to assume that all the oxygen has been removed from the package. The amount of residual air will depend on several factors: equipment, maintenance of the equipment, the product, the speed of operation, package design, etc.

A 5: Far too often we think of a barrier as a shield that keeps intruders out. The walls of a castle were designed to ward off invaders. Yet the bars on a prison cell are equally construed as barriers to keep the incarcerated in.

A 15: It has been well documented that what we eat determines the quality and length of our lives. The wrong foods clog our arteries and are in some way shortening our lives. It is thus important to select both the quality and quantity of nutrients for consumption.

A 10: Preformed pouches are widely used in the packaging of food items. As the volume of product increases, manufacturers turn to form-fill-seal (ffs) equipment to meet the demands of increased productivity. If flat items such as slices of luncheon meat are involved, they can be packaged on machines that form flat pouches around the product. However, high profile products are not suited for such package formation. They must be placed in a tray or a formed blister. Many such items are packaged in rigid trays (10 mils +), either preformed or made in line. The cost of such a package is very high and cannot be justified in many instances. The use of a flexible forming web reduces material cost and speeds production.

A 8: Plastics have found wide acceptance as packaging materials. These modern replacements for wrapping paper fulfill all the packaging requirements: contain, protect, and display—and all that at a relatively low cost. A further innovation of packaging utilizes “rigids” to add quality and a variety of new dimensions to the packaging function. Rigids can be shaped to the contour of the product and thus provide improved visibility.

A 2: The package requirements are often determined by the nature of the product to be packaged. If the product is sensitive to atmospheric conditions such as oxygen, carbon dioxide, acidity, or moisture, then it is often desirable to create an artificial environment around the product, which will be maintained within the package in order to avoid changes in the quality or appearance of the product.

A 25: Bacon is a pork product with a very high fat content. It is sensitive to bacterial decay and should be protected by refrigeration as well as controlled atmosphere packaging. Nevertheless, a goodly portion of bacon is still packaged in tux cartons or simply over-wrapped.

A 28: Fresh meat—beef, veal, pork, and lamb—marketing has undergone some major changes. The small butcher has practically disappeared. Most meat is sold in the supermarket. However, the supermarkets have failed to modernize the butchering operation sufficiently to keep pace with advances in technology. Some claim that the high cost of meat is the consequence of this outdated processing and marketing technique.

A 19: All of us are familiar with canned food products. Anyone who has set foot in a supermarket has seen shelves filled with canned soups, vegetables, fruits, and many other items. Cans have proven themselves over several decades. They are a reliable means for preserving food items at ambient conditions for very prolonged storage cycles (several years, if needed). A can is a metallic container which is capable of maintaining a hermetic seal. Foodstuffs are placed therein and after the metallic can has been sealed it is subjected to a heat sterilization cycle. All bacteria associated with the product are killed in the retort operation, and thus the product in the sealed can may be maintained without spoilage for an almost indefinite period of time at a wide range of temperature and humidity conditions.

A 22: The seafood industry has undergone some very startling changes and yet has in some respects remained the same.

A 31: It is estimated that more than 80% of U.S. households are equipped with microwave ovens. It is thus no wonder that more than $200 million of microwavable packaging material will be consumed in 1990. With all this success there are nevertheless some major problems left to be resolved.

A 26: Frankfurters, frequently also referred to as wieners, are a mass produced processed meat item. The product differs widely in its composition. In all cases, it has a very high percentage of water content, meat, a relatively high fat content, and in some instances also cereal, spices, preservatives, and a variety of other additives. The meat may consist of one or a mixture of the following: beef, pork, and chicken. The ingredients are finely ground, masticated, and eventually emulsified. This emulsion is fed into casings. The frankfurters are thus cured and practically cooked while moving through a smokehouse. The modern smokehouse accommodates huge volume and delivers finished franks at such rapid rates as to require automatic handling of same at the pack off end.

A 24: To better understand the needs of snack food packaging one must review the type of snack foods available and the industry that produces this product.

A 9: Package failure for whatever reason is undesirable. Yet mechanical, material, or personnel imperfection will be encountered. These are transmitted tothe package in one form or another.

A 16: YES … BUT! It is undeniable that we have a solid waste problem. Municipal solid waste has risen from 87.5 million tons in 1960 to 157.7 million tons in 1986. The composition of the waste (see Table 16–1) has changed somewhat over the past 30 years—but not as drastically as the quantity increase might indicate. Paper and paperboard has increased by about 20% in the waste makeup. Plastics have increased almost 15 fold in the same 30-year period. All other components of solid waste have actually declined. One could make a case for paper and plastic packaging having contributed to the increase in solid waste, while cans and glass bottles have diminished in the mix. However, statistics on sanitary food containers are inconclusive in either supporting or contradicting this contention. Unfortunately, the U. S. Department of Commerce has changed classifications in 1987 and thus “paper, coated and laminated, packaging” was established as SIC 2671. Since it was part of SIC 2641, the growth of these items cannot be traced back over the past thirty years. However, in the period from 1987-1990 the increase in packaging materials from 2.2 billion to 2.3 billion dollars is certainly not an untoward rate of growth.

Q 30: The packaging of coffee presents a large array of challenges, opportunities, and difficulties. Coffee gave the impetus to modern packaging and especially to controlled atmosphere (CA) packaging. Back in the 1950s an Italian machine was imported to vacuum pack coffee. Unfortunately, the idea, while very laudable, never worked. The vacuum lines would fill up with ground coffee before the package could be sealed. Eventually, the coffee project was abandoned, but the experience gained helped to found a new industry, CA food packaging. The engineers on this commercial failure went forth and founded a number of successful companies, many of these are still in the forefront of new package design and development.

A 1: The answer to this question is: EVERYBODY! Let us examine just a few examples of the enormous impact packaging has made on our daily lives.

A 27: A large variety of processed meat products are sold under the collective name of “luncheon meat.” A good portion of luncheon meats are sold prepackaged in the supermarket. This is not meant to deprecate the more traditional sale at the local deli or the growing activity at the supermarket deli counter. The consumer very often prefers to have bologna sliced specifically for his (or her) demand. It must be realized that both modes of marketing will survive for some time and actually compliment one another.

A 17: This question unfortunately has no simple answer. The question implies a concern for packaging cost as well as quality. To sacrifice protection of a costly product for the sake of economics in packaging seems ill advised. Thus one seeks minimal expenditure consistent with quality requirements.

A 23: Produce is a very perishable commodity which is subject to a high waste factor. The techniques applied in post-harvest handling, storage, and market display are largely responsible for this high toll. While great advances have been made in improving the yield and speed of agricultural production, there has been relatively little done to extend the shelf life of fresh produce on a commercial scale.

A 12: Far too frequently little thought is given to the suitability of a package as it relates to the product it is meant to contain. Many questions have dealt with the effect of the package on the product. It is only appropriate to consider the potential effect of the product on the package itself.

1-Iodo- and 1,4-diiodo-phthalazines were obtained by treating the corresponding chloro compounds with a solution of sodium (or potassium) iodide in acetone containing hydrogen iodide. These iodophthalazines, on reaction with copper cyanide in pyridine, gave the relevant phthalazinecarbonitriles.

The state-of-the-art programming appliance timer used in washing machines and dishwashers is a bargain, so much a bargain that it is allowed to dictate the functional design of many household appliances. The electronic escapement takes the best features from this timer and combines them with an electronic timing circuit that allows a new range of flexibility. Low-level sensors of many varieties and continuously adjustable timing bases are readily adaptable for work with the electronic escapement. Circuits are shown and examples given showing how the use of the electronic escapement can provide unique circuitry to accomplish control functions otherwise nigh impossible.