Performing calculus: Asymmetric adaptive stimuli-responsive material for derivative control.

Materials (e.g., brick or wood) are generally perceived as unintelligent. Even the highly researched "smart" materials are only capable of extremely primitive analytical functions (e.g., simple logical operations). Here, a material is shown to have the ability to perform (i.e., without a computer), an advanced mathematical operation in calculus: the temporal derivative. It consists of a stimuli-responsive material coated asymmetrically with an adaptive impermeable layer. Its ability to analyze the derivative is shown by experiments, numerical modeling, and theory (i.e., scaling between derivative and response). This class of freestanding stimuli-responsive materials is demonstrated to serve effectively as a derivative controller for controlled delivery and self-regulation. Its fast response realizes the same designed functionality and efficiency as complex industrial derivative controllers widely used in manufacturing. These results illustrate the possibility to associate specifically designed materials directly with higher concepts of mathematics for the development of "intelligent" material-based systems.

The Pathway to Intelligence: Using Stimuli-Responsive Materials as Building Blocks for Constructing Smart and Functional Systems.

Systems that are intelligent have the ability to sense their surroundings, analyze, and respond accordingly. In nature, many biological systems are considered intelligent (e.g., humans, animals, and cells). For man-made systems, artificial intelligence is achieved by massively sophisticated electronic machines (e.g., computers and robots operated by advanced algorithms). On the other hand, freestanding materials (i.e., not tethered to a power supply) are usually passive and static. Hence, herein, the question is asked: can materials be fabricated so that they are intelligent? One promising approach is to use stimuli-responsive materials; these "smart" materials use the energy supplied by a stimulus available from the surrounding for performing a corresponding action. After decades of research, many interesting stimuli-responsive materials that can sense and perform smart functions have been developed. Classes of functions discussed include practical functions (e.g., targeting and motion), regulatory functions (e.g., self-regulation and amplification), and analytical processing functions (e.g., memory and computing). The pathway toward creating truly intelligent materials can involve incorporating a combination of these different types of functions into a single integrated system by using stimuli-responsive materials as the basic building blocks.

Universal Nature-Inspired Coatings for Preparing Noncharging Surfaces.

Static charge generated by contact electrification on surfaces can lead to many undesirable consequences such as a reduction in the efficiency of manufacturing processes, damage to equipment, and explosions. However, it is extremely challenging to avoid contact electrification because it is ubiquitous: almost all types of materials charge on contact. Here, we coated materials with naturally occurring polydopamine (PDA) and tannic acid (TA) for preparing noncharging surfaces. Importantly, these coatings are very versatile and can be coated on a wide range of materials, including metals, inorganic materials, semiconductors, and polymers. Once coated, the amount of charge generated was found to reduce dramatically at different humidities. The reduction in charge may be due to the radical-scavenging property of PDA and TA. This simple general approach is ideal for coating the vast variety of materials that need to resist charging by contact electrification.

Membrane Active Small Molecules Show Selective Broad Spectrum Antibacterial Activity with No Detectable Resistance and Eradicate Biofilms.

Treating bacterial biofilms with conventional antibiotics is limited due to ineffectiveness of the drugs and higher propensity to develop bacterial resistance. Development of new classes of antibacterial therapeutics with alternative mechanisms of action has become imperative. Herein, we report the design, synthesis, and biological evaluations of novel membrane-active small molecules featuring two positive charges, four nonpeptidic amide groups, and variable hydrophobic/hydrophilic (amphiphilic) character. The biocides synthesized via a facile methodology not only displayed good antibacterial activity against wild-type bacteria but also showed high activity against various drug-resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecium (VRE), and ß-lactam-resistant Klebsiella pneumoniae. Further, these biocides not only inhibited the formation of biofilms but also disrupted the established S. aureus and E. coli biofilms. The membrane-active biocides hindered the propensity to develop bacterial resistance. Moreover, the biocides showed negligible toxicity against mammalian cells and thus bear potential to be used as therapeutic agents.

Effect of amide bonds on the self-assembly of gemini surfactants.

This study provides an insight into the micellar aggregation properties in aqueous solutions of various gemini surfactants bearing one or more amide groups at the side chains and/or in the spacer by conductivity and small angle neutron scattering (SANS) studies. The amide functionality was found to enhance the surfactant aggregation properties as compared to the surfactants having no amide bond. Furthermore, the aggregation properties of the gemini surfactants bearing amide groups were found to strongly depend on the position and number of amide bonds. With the increase in the number of amide bonds, the aggregation number (N) and the size of the micelles increased. Additionally, the size and shape of the micelles were also found to depend both on the hydrocarbon chain length and the spacer chain length. It was also found that the aggregation number and the size of the micelles increased with an increase in concentration and decreased with an increase in temperature. The critical micellar concentration (CMC) values of the gemini surfactants obtained by a conductometric method were found to vary greatly with variation in the hydrocarbon chain.