The cosmetics industry is increasingly using sophisticated materials and technologies in their products and to measure their effectiveness. Understanding how these products interact with skin, adhere to skin, and deliver a benefit or create a visible effect leads to better and safer products. An understanding of the optics and mechanics of skin and the cosmetics–skin interface is important for achieving various visual and functional effects. This issue reviews the underlying science and the technical challenges behind the development of materials for the personal care and cosmetics industry.

This article gives the foundation for understanding the structure and function of human skin and its layers. Skin is our first line of defense against the penetration of external chemicals and bacteria into the body and of water loss from the body. Skin's visual and tactile properties are very much linked to appearance and beauty. Skin treatments as simple as washing with soap affect the mechanics of skin properties, making it dry and brittle versus smooth and elastic. Likewise, natural aging, hormonal changes, and sun exposure affect the properties of skin. Mild cleansing, moisturizer treatments, and regular use of sunscreens can, however, help skin maintain and even improve its quality, appearance, and functional properties.

Nature exhibits a variety of remarkable phenomena that are useful but difficult to imitate in real life. Examples are the “touch me not” plant (Mimosa pudica), which folds up upon being attacked, or microbes that deposit on ocean vessels even under hostile conditions. Understanding the mechanisms governing these phenomena can prove powerful for developing new classes of cosmetic products. This article examines the development of novel materials with functional properties such as controlled delivery and the deposition of sensory attributes (fragrances, flavors, etc.) desirable in cosmetic products. Particularly, systems based on polymer/surfactant chemistry are explored for achieving transport and release of cosmetic and pharmaceutical molecules at desired rates. The hybrid polymers and nanogel particle systems discussed here represent new classes of materials with nanodomains that can be tuned to extract and deliver cosmetic attributes by means of changes in natural parameters such as temperature and pH. While the safety of existing nanomaterials marketed for decades has not been an issue, methods are urgently needed to validate the toxicological safety of future nanomaterials.

Cosmetics are products that are designed to maintain or improve visual appearance when applied to skin. Skin is a mechanically flexible substrate that changes in chemical and surface properties during the course of the day. Sebum (an oily substance secreted by the sebaceous glands) and perspiration (a secretion of mostly salt water by the eccrine glands) as well as environmental insults work counter to the desired benefits of cosmetics on physical appearance. Recent advances in the ability to control morphology and chemical properties have led to novel materials that in turn have enabled the development of cosmetics that provide, on the one hand, a more natural look, and on the other, unique and unprecedented visual effects. Progress in understanding skin biomechanics and surface properties lead to product formulations with unprecedented wear and performance characteristics. This article reviews recent advances in the ability to control the optical, bulk, and surface properties of materials, and their application to improved cosmetic formulations.

A cosmetic product is often a complex non-homogeneous mixture of physicochemical units including polymers, small molecules, surface-active species, and particles. In use, it is applied to an equally heterogeneous substrate, skin. Consequently, materials structure as well as composition and the nature of the surfaces are relevant to a clear understanding of any technologically important product property or process. No longer is it sufficient to answer the classical questions of analysis—what and how much?—for many applications; we must now ask the additional questions of where, how organized, and how is it manifest to the customer? Although analytical sciences have, for many years, been applied to the problem of characterizing what is in chemical systems, the need to understand spatial and interfacial interactions has received much less attention. The explosive growth, however, in electronics, computing, biology, mathematical methodologies, microscopy, and optics now present the cosmetic industry with a new set of tools that can be utilized to address this issue. It is the objective of this article to highlight some of these measurement advances and how they might have relevance in the cosmetics industry in the coming years.

Silicone polymers have become increasingly important as ingredients in skin care products, and the trend has accelerated over the last decade. While silicone compounds have existed since the 1860s, their increasing popularity in recent years is due in large part to a better understanding of their unique functions. This increased understanding of the properties of silicone, coupled with an increased ability of the silicone chemist to modify compounds, has resulted in more effective utilization of these materials in skin care formulations. Silicone polymers bring to formulations a phase that is soluble neither in oil nor in water. They are third-phase ingredients that when properly chosen can provide to formulations properties including surface-tension reduction, wetting, and emulsification.

I am humbled and honored to be here to tell you about a topic that is dear to everyone's heart—and vital to the future of our planet. My colleague, Richard Smalley, gave a presentation on this topic several years ago, at a similar MRS plenary session. Over the last few years of Dr. Smalley's life, he and I worked together, traveling across our country to deliver a message about a subject that we—like many others, both scientists and lay people— have come to believe is unequivocally the most important technological problem in the world: our global energy future. That is an incredibly powerful statement, one that during the next hour I hope to ably defend.