Biomimetic photo-actuation: sensing, control and actuation in sun-tracking plants

Abstract

Although the actuation mechanisms that drive plant movement have been investigated from a biomimetic perspective, few studies have looked at the wider sensing and control systems that regulate this motion. This paper examines photo-actuation-actuation induced by, and controlled with light-through a review of the sun-tracking functions of the Cornish Mallow. The sun-tracking movement of the Cornish Mallow leaf results from an extraordinarily complex-yet extremely elegant-process of signal perception, generation, filtering and control. Inspired by this process, a concept for a simplified biomimetic analogue of this leaf is proposed: a multifunctional structure employing chemical sensing, signal transmission, and control of composite hydrogel actuators. We present this multifunctional structure, and show that the success of the concept will require improved selection of materials and structural design. This device has application in the solar-tracking of photovoltaic panels for increased energy yield. More broadly it is envisaged that the concept of chemical sensing and control can be expanded beyond photo-actuation to many other stimuli, resulting in new classes of robust solid-state devices.

Morphing in nature and beyond: a review of natural and synthetic shape-changing materials and mechanisms

“…With current technology and materials, creating nanostructured materials in complex shapes requires either multiple steps (e.g. alignment followed by assembly), or dual development of materials and manufacturing (for example, alignment of fibre constructs during additive manufacture) [138,140,143].…”

“…Dicker et al propose a synthetic analogue to the sun-avoiding Cornish Mallow leaf, using a chemically responsive hydrogel rendered light-sensitive with the addition of photobase, with particular applications for passive control of solar panels [143]. Finally, cyclic motions are also possible: a BelousovZhabotinsky oscillating chemical reaction has been demonstrated in a hydrogel, creating a cyclic 'walking' motion reminiscent of self-sustaining responses seen in biology [144].…”

Form Follows Environment: Biomimetic Approaches to Building Envelope Design for Environmental Adaptation

“…The processes of transmission, reflection, refraction, scattering, absorption, and interception are basic means to interacting with a medium for filtering, illuminating, and harnessing light in nature [62]. For example, the silver ragwort scatters light to filter and reduce incident light [81]; the Venus flower-basket illuminates by transmitting light through its intricate structure [82,83]; and some plants maximize interception to harness light [84][85][86].…”

Biomimetic photo-actuation: progress and challenges

“…Although it may seem that the simplified solution offered by smart material actuators is preferable, such an approach struggles to accommodate complexities such as the physical separation of sensing and actuating locations, multiple or distributed sensors, or the ability to apply computation, control regimes or simple filtering between the sensing and actuating functions. In this work we explore biomimetic photo-actuation with a case study of a sun-tracking plant, the Cornish Mallow (Lavatera cretica L.), to reveal how Nature creates efficient and robust intelligent structures, while still allowing for the complexities required for rich adaptivity 1 .…”

“…As shown in Video 1, the Cornish Mallow (Lavatera cretica L.) reversibly moves its leaves throughout the day such that they remain facing the moving sun. This property, termed heliotropism, involves the generation, transport and manipulation of chemical signals from a distributed network of sensors in the leaf veins to a specialized osmosis driven actuation region in the leaf stem 1 . It is this spatial separation of the location of stimulus recognition (light sensing) and response (actuation), which can allow biomimetic systems that share the operating principles of the Cornish Mallow to overcome the constraints of smart material actuators.…”