Nature-inspired innovation, also known as biomimicry, biomimetics or biologically-inspired design, involves learning from living nature to develop technical applications.

There are two main approaches used in the process:

1. The biology push process (bottom-up approach) - A technical product is developed based on the study of forms, functions, processes and interaction principles discovered through biological and ecological research. 

2. The technology pull process (top-down approach) - Biomimetic improvements are sought for an existing technical product.

This article will compare and contrast these two approaches, drawing insights from various research centres worldwide.

The Biology Push Process 

In the bottom-up biology push approach, the starting point is a fascinating biological phenomenon or mechanism that is studied in detail to understand the underlying functional principles. This basic biological research then inspires the development of a novel technical product mimicking that biological function.

A prime example is the development of the self-cleaning facade paint Lotusan®, which was directly inspired by the discovery of the self-cleaning properties of lotus leaves (Nelumbo nucifera). Botanists Wilhelm Barthlott and Christoph Neinhuis at the Botanical Garden in Bonn, Germany deciphered that the micro- and nano-rough surface of lotus leaves, covered in waxy crystalloids, allows water droplets to easily roll off, picking up dirt particles. This minimizes the contact area between the surface and contaminants. By mimicking this hierarchical surface structure, the highly water-repellent, self-cleaning paint Lotusan® was engineered and has been on the market since 1999.

Another example of the biology push process is the development of the "Technical Plant Stem" at the Botanic Garden Freiburg. Inspired by the lightweight yet stable hollow stems with thin walls found in horsetails, bamboo, and giant reeds, biologists and engineers developed and patented an artificial structure that combines lightweight construction with mechanical robustness by mimicking the stem anatomy.

The biology push process allows truly innovative, outside-the-box solutions to be developed by starting from a blank slate. It follows a "solution-based" biomimetic approach, where a fascinating biological phenomenon is the starting point that inspires technical applications. However, it requires in-depth biological research as the first step and there is no guarantee the functional principles can be successfully translated to a viable product. The process relies on an interdisciplinary knowledge transfer from biology to engineering and design.

The Technology Pull Process

In contrast to the bottom-up biology push approach, the top-down technology pull approach begins with an existing technical challenge or product that needs improvement. Relevant biological models are then sought out to inspire solving the engineering problem.

A prime example is the development of the biomimetic facade shading system Flectofin®. Architects and engineers wanted to create an adaptive shading system with adjustable fins, but without using mechanical hinges that are prone to wear and tear. They looked to the bird-of-paradise flower (Strelitzia reginae) for inspiration. The flower has a flexible perch that deforms and opens under the weight of a bird, exposing the pollen. By studying this deformation mechanism, called lateral-torsional buckling, the researchers were able to design the Flectofin® shading system. It has a flexible glass-fibre reinforced plastic backbone that bends to open and close the shading fins, without requiring mechanical hinges.

Another case of the technology pull approach is the development of the Flectofold facade shading system, inspired by the underwater carnivorous waterwheel plant (Aldrovanda vesiculosa). The aim was to create a folding shading system with a flexible midrib and lifting wings. Biologists studied how the curved midrib of the waterwheel's snap trap stores elastic energy that is released to rapidly close the two lobes. This principle was abstracted and implemented in the Flectofold system, where the bending of the midrib lifts the shading wings.

The snap trap of the Venus flytrap (Dionaea muscipula) provided inspiration for the design of a soft robotic gripper. The goal was to develop a gripper that could gently grasp and release objects of various shapes and sizes. By studying how the Venus flytrap's lobes elastically deform to rapidly enclose prey, researchers designed a silicone gripper with a similar bistable snapping mechanism actuated by compressed air.

Starting with clear technical requirements, the technology pull process provides focus and direction to biomimetic research. Relevant biological models can be efficiently identified and studied to abstract the key functional principles. However, this targeted approach may be more limited in the novelty of the solutions, as it is constrained by the initial technical problem definition. The technology pull process represents a "problem-driven" biomimetic approach, where a technical challenge is the starting point that guides the search for biological inspiration.

The top-down technology pull approach enables biomimetic innovations focused on improving existing technologies, guided by specific engineering needs. It complements the bottom-up biology push approach that allows unconstrained exploration of fascinating biological phenomena to inspire novel applications. As illustrated by the various examples of plant-inspired adaptive shading systems and soft robotics, the technology pull approach has led to the successful development of high-performance biomimetic products.

Conclusion

In summary, the biology push and technology pull approaches represent complementary strategies in biomimetics. The bottom-up biology push allows breakthrough innovation inspired by fascinating biological research, while the top-down technology pull enables targeted improvements to existing products guided by technical needs. As illustrated by the Lotusan® and Flectofin® examples, both approaches have led to the successful development of biomimetic products.

Combining the two approaches, where interesting biological phenomena are matched to relevant technical applications, may provide the optimal path forward for future nature-inspired innovations.