DNA-controlled Spatio-temporal Patterning of Active Matter

Molecular programs and active matter appear as two key ingredients for the emergence of shape in living systems. The former process chemical information, while the latter generates long-range mechanical forces. The coupling of these two elements is thus essential for the synthesis of life-like materials. Here, we describe the preparation of DNA-responsive surfaces that shape a cm-scale tridimensional active gel comprised of microtubules: a DNA signal triggers the gel, structuring it into a periodic band pattern or local aggregates, depending on its sequence and concentration. Finally, we show how a gradient of DNA concentration transfers its positional information to the active gel, mimicking chemo-mechanical patterning promoted by morphogens during embryo development. We anticipate that such DNA-controlled active matter will contribute to the development of life-like materials with self-shaping properties.

Stimuli-responsive surfaces for switchable wettability and adhesion

Diverse unique surfaces exist in nature, e.g. lotus leaf, rose petal and rice leaf. They show similar contact angles but different adhesion properties. According to the different wettability and adhesion characteristics, this review reclassifies different contact states of droplets on surfaces. Inspired by the biological surfaces, smart artificial surfaces have been developed which respond to external stimuli and consequently switch between different states. Responsive surfaces driven by various stimuli, e.g. stretching, magnetic, photo, electric, temperature, humidity and pH, are discussed. Studies reporting on either atmospheric or underwater environments are discussed. The application of tailoring surface wettability and adhesion includes microfluidics/droplet manipulation, liquid transport and harvesting, water energy harvesting and flexible smart devices. Particular attention is placed on the horizontal comparison of smart surfaces with the same stimuli. Finally, the current challenges and future prospects in this field are also identified.

Poly(l-lactide)-Based Anti-Inflammatory Responsive Surfaces for Surgical Implants

In the last few decades, surgical implants have been widely used to restore the function of damaged bones or joints. However, it is essential to receive antibiotic or anti-inflammatory treatment to circumvent significant problems associated, such as the colonization of the implanted surface by bacteria or other microorganisms and strong host inflammatory responses. This article presents the effectiveness of the copper catalyzed alkyne-azide cycloaddition (CuAAC) (“click”) reaction by the linkage of a fluorophore to the poly(L-lactide) (PLLA) surface. The results were analysed by means of X-ray photoelectron spectroscopy (XPS), contact angle and fluorescence microscopy. Moreover, this current work describes the covalent immobilization of the anti-inflammatory drug indomethacin on a PLLA surface. The CuAAC click reaction was selected to anchor the drug to the polymeric films. The successful bioconjugation of the drug was confirmed by XPS and the change on the contact angle.

Smart Surfaces with Tunable Wettability

Modification of surface wettability (ranging from complete wetting to complete non-wetting) of various surfaces is often required in many applications. Conventionally, it is done using a coating of suitable materials as per the requirement. In this approach, the old coating needs to be replaced every time by a new appropriate one. Alternatively, smart responsive surfaces can show tunable wettability with external stimulus. Electric field, temperature, light, pH, mechanical strain, etc. can be effectively used as external stimuli, and a suitable coating can be incorporated, which responses to the respective stimulus. These surfaces can be used to tune the surface wettability to any extent based on the magnitude of the stimulus. The primary role of the external stimulus is to vary the liquid-solid interfacial energy, which subsequently changes the surface wettability. The biggest advantage of this approach is that the surface wettability can be reversibly tuned. Each of the techniques mentioned above has many advantages along with certain limitations, and the combination of advantages and limitations helps users to choose the right technique for their work. Many recent studies have used this approach to quantify the tuning of the surface wettability and have also demonstrated its potential in various applications.

Electroresponsive Polyelectrolyte Brushes Studied by Self-Consistent Field Theory

End-grafting of polyelectrolyte chains to conducting substrates offers an opportunity to fabricate electro-responsive surfaces capable of changing their physical/chemical properties (adhesion, wettability) in response to applied electrical voltage. We use a self-consistent field numerical approach to compare the equilibrium properties of tethered strong and weak (pH-sensitive) polyelectrolytes to applied electrical field in both salt-free and salt-containing solutions. We demonstrate that both strong and weak polyelectrolyte brushes exhibit segregation of polyions in two populations if the surface is oppositely charged with respect to the brush. This segregation gives rise to complex patterns in the dependence of the brush thickness on salt concentration. We demonstrate that adjustable ionization of weak polyelectrolytes weakens their conformational response in terms of the dependence of brush thickness on the amplitude of the applied voltage.

Epoxide and oxetane based liquid crystals for advanced functional materials

This work highlights the application of epoxide and oxetane liquid crystals in advanced functional materials including soft robotics, responsive surfaces, and photonic coatings.