A conceptual example implementation of manual and self-sensing cells in a linear array, constrained between fixed end boundaries, with the switch of the manual cell closed. Small spots indicate the cell is not actuated and large spots indicate the cell is actuated.
A conceptual example implementation of manual and self-sensing cells in a linear array, constrained between fixed end boundaries, with the switch of the manual cell closed. Small spots indicate the cell is not actuated and large spots indicate the cell is actuated.

Smart materials that behave like an artificial skin and can mimic the camouflage of cephalopods such as squid have been developed by a team from the University of Bristol in the UK. Their system was inspired by biological chromatophores that produce patterns that change and morph over time and mimic biological patterning, and demonstrates how to mimic patterning seen in cephalopods, such as the passing cloud display, and other complex dynamic patterning.

The ultimate goal is to create an artificial skin that can mimic such pattern generation techniques for a range of compliant devices such as cloaking suits and dynamic illuminated clothing. These cloaking suits could find uses for blending into different environments, while the framework could also help in signaling – for instance, luminescent distress signals that help in in search and rescue operations.

As reported in the Journal of the Royal Society Interface [Fishman A. et al. J. R. Soc. Interface (2015) DOI: 10.1098/rsif.2015.0281], the team detailed the design, mathematical modelling, simulation and analysis of a dynamic biomimetic pattern generation system. To achieve this, the system uses local rules in the artificial chromatophore cells to help them sense their surroundings and then manipulate their change. Through modelling sets of artificial chromatophores in linear arrays of cells, the team assessed if the system could produce a range of different patterns.

The bio-inspired artificial skin is fabricated from thin sheets of a compliant smart material called an electroactive dielectric elastomer, a soft, rubbery material that can be electrically controlled. It is able to mimic the action of biological chromatophores – small pigmented cells embedded on cephalopods skin that expand and contract to change skin color and texture, which they use for rapid and versatile camouflaging and signaling from networks of pigmented, muscle-driven chromatophore cells.

These cells are neurally stimulated to actuate and affect local skin coloring, allowing them to adopt different dynamic and complex skin patterns, including the passing cloud display, where bands of color spread like waves across the skin, a visual effect that works to distract and divert predators.

The team hopes to investigate altering the system to enhance propagation control, as well as producing new patterns using other local rules, and to develop the model to simulate patterns in two-dimensional array systems, which could offer more patterns that resemble those in the natural world. They are also looking into the possibility of producing a prototype from the system, both of the linear arrays of cells and two-dimensional systems.