What have these three scenarios got in common? The tin of baked beans that urges you to buy it as you pass along the supermarket aisles (assuming you still shop for goods and they are not all delivered via the internet), the smart microwave that has your steaming plate of lasagne ready the moment you arrive, following a mobile call to your smart home on the way borne (assuming you still go out to work), and the pill bottle that alerts the health centre if an elderly relative forgets their medication. They are all visions of a future in which the package does more than just contain and protect its contents - it plays an active and sometimes ‘Intelligent’ role in adding functionality to the product itself, or to aspects of product consumption, convenience or security.
Smartness in Packaging
‘Smartness’ in packaging is a broad term that covers a number of functionalities, depending on the product being packaged, including food, beverage, pharmaceutical, household products etc. Examples of current and future functional ‘smartness’ would be in packages that
• Retain integrity and actively prevent food spoilage (shelf-life)
• Enhance product attributes (e.g. look, taste, flavour, aroma etc)
• Respond actively to changes in product or package environment
• Communicate product information, product history or condition to user
• Assist with opening and indicate seal Integrity
• Confirm product authenticity, and act to counter theft.
Smart Packaging and Activated Packaging
There is an important distinction between package functions that are smart/Intelligent, and those that become active in response to a triggering event, for example, filling, exposure to UV, release of pressure etc and then continue until the process is exhausted. Some smart packaging already exists commercially and many other active and intelligent packaging concepts are under development, table 1. A good example of active packaging is the highly successful foam-producing ‘widget’ in a metal can of beer. Another is the oxygen scavenging MAR technology patented by CMB Packaging Technology (now Crown Cork & Seal).
Table 1. Smart packaging under development.
• Oxygen scavenging
• Ethylene scavenging
• Odour and flavour absorbing/releasing
• Moisture absorbing
• Time-temperature history
• Microbial growth indicators
• Light protection (photochromic)
• Physical shock indicators
• Leakage, microbial spoilage indicating
How Activated Packaging Systems Work
This consists of a matrix polymer, such as PET, an oxygen scavenging/absorbing component and a catalyst. The oxygen-scavenging component is a nylon polymer (MXD6) melt blended with the PET at around the 5% level. The catalyst is a cobalt salt added at a low concentration (less than 200ppm) that triggers the oxidation of the MXD6. The OXBAR system remains active for periods of up to two years providing protection to oxygen sensitive products such as beer, wine, fruit juice and mayonnaise throughout their shelf-lives. Active food packaging systems using oxygen scavenging and anti-microbial technologies (e.g. sorbate-releasing LDPE film for cheese) have the potential to extend the shelf-life of perishable foods while at the same time improving their quality by reducing the need for additives and preservatives.
How Intelligent Packaging Works
In ‘intelligent’ packaging, the package function switches on and off in response to changing external/internal conditions, and can include a communication to the customer or end user as to the status of the product. A simple definition of intelligent packaging is ‘packaging which senses and informs’, and nowhere does this generate a more potent vision than within the smart home of the future.
Factors That Will Aid the Growth of Intelligent Packaging
Consumer and societal factors are likely to drive the adoption of smart packaging in the future. The growing need for information on packaging will mean there has to be a step change in providing this information. Consumers increasingly need to know what ingredients or components are in the product and how the product should be stored and used. Intelligent labelling and printing, for example, will be capable of communicating directly to the customer via thin film devices providing sound and visual information, either in response to touch, motion or some other means of scanning or activation. Voice-activated safety and disposal instructions contained on household and pharmaceutical products will be used to tell the consumer how they should be disposed of after consumption - information that can be directly used in the recycling industry to help sort packaging materials from waste streams. Drug delivery systems in smart packaging will be programmed to communicate patient information back to healthcare centres.
Quality Assurance Using Intelligent Labels
Another important need is for consumer security assurance, particularly for perishable food products. The question as to whether, for example, a chilled ready-meal is safe to use or consume is currently answered by ‘best by’ date stamping. However, this does not take into account whether the product has inadvertently been exposed to elevated temperatures during storage or transportation. In the future, microbial growth and temperature-time visual indicators based on physical, chemical or enzymatic activity in the food will give a clear, accurate and unambiguous indication of product quality, safety and shelf-life condition. As an example, COX Technologies has developed a colour indicating tag that is attached as a small adhesive label to the outside of packaging film, which monitors the freshness of seafood products. A barb on the backside of the tag penetrates the packaging film and allows the passage of volatile amines, generated by spoilage of the seafood. These are wicked passed a chemical sensor that turns FreshTag progressively bright pink as the seafood ages, figure 1.
Figure 1. Colour indicating tags attached as a small adhesive label to the outside of packaging film can be used to monitor the freshness of perishable food products such as seafood.
Intelligent Packaging for Fresh Fruit and Vegetables
Fresh-cut produce continues to be one of the fastest growing segments of food retailing and while conventional film packaging is suitable for lettuce and prepared salads, it cannot cope with the high respiration rates of pre-cut vegetables and fruit, leading to early product deterioration. In the USA, novel breatheable polymer films are already in commercial use for fresh-cut vegetables and fruit. Landec Corporation supplies Intellipac packaging films that are acrylic side-chain crystallisable polymers tailored to change phase reversibly at various temperatures from 0-68°C. As the side-chain components melt, gas permeation increases dramatically, and by further tailoring the package and materials of construction, it is possible to fine tune the carbon dioxide to oxygen permeation ratios for particular products. The final package is ‘smart’ because it automatically regulates oxygen ingress and carbon dioxide egress by transpiration according to the prevailing temperature. In this way, an optimum atmosphere is maintained around the product during storage and distribution, extending freshness and allowing shipping of higher quality products to the consumer.
Self-Heating and Self-Chilling Packaging
Improved convenience is a value-added function that customers are likely to pay extra for as lifestyles change. Self-heating packages, for soup and coffee, for example, and self-cooling containers for beer and soft drinks have been under active development for more than a decade, but have yet to achieve commercial status. However, Crown Cork & Seal is pioneering the development of a self-chilling beverage can in conjunction with Tempra Technologies and development is nearing completion. The Crown/Tempra technology uses the latent heat of evaporating water to produce the cooling effect. The water is bound in a gel layer coating a separate container within the beverage can, and is in close thermal contact with the beverage. The consumer twists the base of the can to open a valve, exposing the water to the desiccant held in a separate, evacuated external chamber This initiates evaporation of the water at room temperature. The unit has been designed to meet a target specification set by major beverage customers cooling 300ml of beverage in a 355ml can by 16.7°C in three minutes. This performance level has been achieved in laboratory tests and working samples are currently undergoing focus group trials with customers.
Give a self-heating or self-cooling container a sensor to tell the consumer it is at the correct temperature and the package becomes ‘smart’ (such packaging is currently under development). The most common use a thermochromic ink dot to indicate the product is at the correct serving temperature following refrigeration or microwave heating. Plastic containers of pouring syrup for pancakes can be purchased in the USA that are labelled with a thermochromic ink dot to indicate that the syrup is at the right temperature following microwave heating. Similar examples can be found on supermarket shelves with beer bottle labels that incorporate thermochromic-based designs to inform the consumer when a refrigerated beer is cold enough to drink.
Smart Packaging Concepts for Pharmaceuticals
Smart packaging concepts that improve case of use could include ‘dial-a-dose’ smart caps and closures that allow the safe dispensing of exact controlled quantities of product, e.g. pharmaceuticals, cleaning materials, and other potentially hazardous materials. Already a prescription drug bottle with bottle cap alarm is available - it beeps to alert users when it is time to take the medication, and it displays how many times the bottle has been opened and the intervals between openings. The bottle can be connected via a modem to the healthcare centre for the automatic transmission of drug usage and, if necessary, provide feedback to the patient if not in compliance. Eventually, programmed skin patches using smart gels that rely on changes in skin properties to trigger drug delivery could replace conventional pill-taking medication.
Intelligent Tamper-Proof Packaging
Knowing whether a package has been tampered with is equally important to consumers. Tamper evidence technologies that cannot easily be replicated, e.g. based on optically variable films or gas sensing dyes, involving irreversible colour changes, will become more widespread and cost-effective for disposable packaging of commodity items. Piezoelectric polymeric materials might be incorporated into package construction so that the package changes colour at a certain stress threshold. In this way, a 'self‑bruising' closure on a bottle or jar might indicate that attempts had been made to open it.
Easier to Open Packaging
Easier to open packaging will be a paramount feature of future packaging. A recent DTI survey showed that in the UK in 1997, 90,964 accidents requiring hospital treatment were packaging related. The focus will be on better design (size, shape, etc.) and the optimum use of materials, to produce easy to open packages consistent with the strength capabilities of an ageing population. Developments in low peel-force adhesives and structures, even smart packages that are self-opening, e.g. based on shape memory alloys (the metal ‘rubber’ band), can be envisaged.
Possible Concerns over Intelligent Packaging
When it comes to the environment, consumer attitudes towards packaging are generally confused and contradictory. There are increasing concerns about the amount of waste created by packaging, but the growth of more elaborate and attractive packaging is being driven by consumers to fuel our desire for convenience and feed our lifestyle choices. Ultimately, future consumers could react negatively to the perception of increased waste and lack of recyclability of disposable smart packages. The perception of extra cost and complexity, and the possible mistrust/confusion of technology - for example, if there is both a date stamp and a visual indicator on a food pack, which does the customer take note of? - are further factors that could slow widespread market introduction of smart packages. The overall acceptance barriers to smart packaging can be summed up as:
• Extra cost - can it be absorbed/passed on to consumer?
• Unreliability of indicating devices - showing either food to be safe when it is not (potential liability?) or food to be unsafe when it is (increased spoilage stock loss)
• Food safety and regulatory issues - e.g. possible migration issues of complex packaging materials into product
• Recycling features and environmental regulations.
What Areas will Benefit from Intelligent Packaging First?
Cost issues will probably mean that early adopters of smart packaging are likely to be in non-commodity products, e.g. pharmaceuticals, health and beauty, and packaging that plays a part in lifestyle and leisure activities. A further consideration is the need for education to reassure the consumer of package safety, and ensure against incorrect operation and mistrust of smart technology. The successful adoption of smart packaging concepts in the future must create advantages for the whole of the supply chain.
The Future for Packaging
The vision of the future of packaging, according to the recently published Foresight report ‘Materials: Shaping Our Society’, is one in which the package will increasingly operate as a smart system incorporating both smart and conventional materials, adding value and benefits across the packaging supply chain. For smart materials to be adopted in packaging, they need to be inexpensive relative to the value of the product, reliable, accurate, reproducible in their range of operation, and environmentally benign and food contact safe.
Lessons in Packaging Learned from Nature
Perfect packaging exists in nature - examples include the banana and the egg, together with the many smart materials and systems that control plant and biological functions. Learning from Nature to solve engineering problems (biomimetics) is not new, although the term itself is. In 1850, Joseph Paxton gained his inspiration for the design of the Crystal Palace in London from a study of the structure of the lilypad, Victoria amazonica. At the Centre for Biomimetics at the University of Reading, researchers are studying expanded starch in the search for a sustainable alternative to polystyrene, used extensively in the secondary packaging of consumer goods. Another team is looking at smart fabrics by examining polymer analogues to plant leaf structures controlling respiration, or humidity control, based on the opening and closing of pine cones. Research groups at other institutions are studying how helmet design could give improved head protection by looking at the energy absorbing properties of the hazelnut shell and the skull of the woodpecker. A spin-off application is in the packaging and transportation of fragile goods. Animals and plants have evolved many successful structural and functional mechanisms and increasing our study of biological materials and systems will almost certainly yield promising engineering concepts applicable to smart packaging. Packaging in the future could indeed be ‘smart by name, smart by Nature!’