Bioinspired materials and surfaces

Nature provides many important lessons on material design and processing. In biology, evolution is the designing process, which has led to many fascinating materials systems in terms of structure, functionality, and performance. Marine mussels use a cascade of proteins to achieve their strong and durable adhesion in ocean water, which is still a great challenge for many synthetic adhesives.  The cuticle of insects and other arthropods is a great example of fiber reinforced composite materials with rather complex and hierarchical structures using chitin and protein building blocks. The goal of our research is to use engineering design principles to analyze biological systems to evaluate the quality of biological material designs, and to develop novel materials inspired by the biological systems with advanced mechanical, optical, and biomedical properties.

 

funcTIonal polymer surfaces

Surface tethered polyelectrolyte brushes can adapt to surrounding environments in response to external stimuli. Such polyelectrolyte brushes are becoming highly important in a wide range of practical applications, such as cell adhesion, drug delivery, lubrication, sensors, coatings, and water filtration. In many of these applications, the brushes are not able to achieve equilibrium on an operational time scale, and therefore the dynamic (time- and rate- dependent) surface forces (i.e., repulsion, adhesion, and friction) of polyelectrolyte brushes and the kinetics of their structural change in the presence of external stimuli are most relevant. We are exploring the connection between the kinetic structural change of polyelectrolyte brushes and their dynamic surface forces, especially frictional forces upon having external stimuli, which is critical to many of the applications mentioned above.

 

Flexible skin sensors

Increasingly health concerns arising from an ageing society and poor modern lifestyle habits pose a heavy burden on healthcare system, presenting new requirements for personalized real-time health status monitoring.  Our aim is to build a platform (flexible sensor) that could analyse important ionic and metabolic biomarks in human sweat via an integrated on-skin flexible device.  Apart from the development of flexible skin sensors, we also explore new materials that can improve the performance of various flexible sensors, such as conductive hydrogels and structured adhesives. We are particularly interested in applying our bioinspired materials to the flexible electronic devices to improve the performance of the sensors.

 

Beyond-equilibrium Materials

Soft interfaces such as polymer surfaces and cell membrane are often not at thermodynamic equilibrium. Their properties are governed by dynamic (time- and rate-dependent), non-equilibrium interactions that occur during for example, manufacturing processes, but much of our understanding on such systems is based on at-equilibrium concepts. The successful development and technological realization of next-generation functional soft surfaces will likely depend upon transitioning from equilibrium materials to materials with multidimensional, hierarchical structures and beyond-equilibrium properties. Such a transition will require understanding of and control over materials interactions at the nanoscale. Interactions that hold soft materials together are often comparable in magnitude to the thermal energy; therefore small external perturbations (e.g., temperature, mechanical stress, and light) can induce macroscopic molecular reorganizations. The molecular structure of soft interfaces can therefore be tailored to achieve optimal functionalities on different time and length scales.