Embedded Movement Responsive Shape-changing Surfaces

By embedding responsive shape-changing materials into flexible surface structures, surfaces can be created that are no longer understood as passive envelopes, covers or carrier materials, but rather as operative systems 1. Examples can be found in facade design 2, interior design, human-computer-interaction 3 4 and fashion 5. These Surfaces can act for example as adaptive shading systems, can influence room acoustics, are used as tangible interfaces or enable variable breathability in sportswear. Such current developments can be grouped into two categories. Innovations in the field of so-called smart materials, functional materials, (flexible) microelectronics and micro-robotics enable the development of surface-systems in which mechanics, actuators, sensors and control elements are reduced to a minimum and are embedded in the surface-structure itself. Sensors are selected according to the information that is to be gathered, and the desired response mode of the actuator can be programmed 6. These surfaces may be called operated adaptive surface systems. In addition, under the term Active Matter, flexible surfaces and membrane structures are developed which, due to the operative character of the material itself, have the ability to react autonomously to on information in their environment. Structures and mechanics inherent to materials are used and manipulated to enable adaptive responses 7. This design strategy allows an energy-autonomous function and resource-efficient construction of kinetic surfaces. In contrast to the first-mentioned operated adaptive surface systems, the behaviors of these active surfaces are already definitively defined during manufacturing process, so they cannot be re-programmed at a later point in time.
Embedded Movement is located at the intersection of these two areas of research and development. The project aims to investigate how flexible surface systems can be given kinetic and sensory functional potentials without losing typical textile properties such as deformability, lightness and reduced composition. This involves the development of strategies for generating surface movements, the investigation of the over-layering of multiple functional potentials as well as the design and the analysis of the behavior of these adaptive Surfaces.

Strategies to enable shape change abilities

Current developments in the field of kinetic-variable surfaces are based on a variety of different movement mechanisms. When it comes to designing the kinetic functions as an integral part of a surface, motion principles which are based on the interplay of two materials are of particular interest. The kinetic potential of such surface systems is created by the controlled and precise combination of two materials and their properties in to a surface structure. Thereby, at least one of these materials has the capacity to significantly change its material properties when a certain activation energy (e.g. heat, moisture or electrical voltage) is applied 8. In the 3D printed work Programmable Wood, for example, the combination of wood filament with PLA-filament enables controlled surface deformations when the air humidity rises. The property of wood fibers to expand when absorbing moisture is used here as the engine for the shape change. On the other hand, the locations of movement and the directions of deformation are mainly determined by the moisture-repellent parts of the surface structure 9. Within the PhD project Embedded Movement, movement mechanisms of this kind are analyzed and material- as well as movement-experiments are realized. This allows to categorize and evaluate strategies of movement generation within active composite materials from a design perspective and to develop corresponding constructive design methods. Manufacturing techniques that enable a precise assembly of materials into surfaces, such as textile techniques, 3D printing and casting processes, are used in this process.

Within initial investigations regarding strategies for motion generation, a manufacturing process was developed that allows Shape memory alloys wires (SMA) to be seamlessly integrated into surface structures using 3D printing (fig. 2). SMAs are transformative materials which, due to their special atomic grid structure, have the property of remembering a previously programmed shape when a certain activation temperature is reached. This activation temperature can be achieved either by applying electric current or when the ambient temperature rises 10. Within Embedded Movement SMA was used which, when activated, shortens by 5% of the total length. By 3D printing, the placement of the SMA wires can be done so precisely that the property of the wires to shorten minimally when heated can be used for spatial surface movements. The second but no less important material of this shape-changing composite is the 3D-printed thermoplastic polyurethan (TPU). Due to the degree of flexibility that this material shows depending on its material thickness and the precise arrangement of hereby flexible and less flexible areas, the transformation of the surface structure can be designed. At the same time, the TPU provides the reset-force for the SMA through its material tension.

Multifunctionality

Looking at the kinetic properties of the surface categories mentioned at the beginning, it is recognizable that the shape-changes of both areas are often limited to one-dimensional back-and-forth movements. As a result, they can, for example in the field of adaptive building envelopes, mostly only take on one function. When incorporating appropriate sensory capabilities, surfaces with multiple deformation potentials could acquire multiple adaptive capabilities. At the same time, combinations of deformations enable complex kinetic responses. By overlaying motion-generating structures, the use of different materials with variable properties and the integration of microelectronics, Embedded Movement explores how multiple kinetic and sensory potentials can be integrated into surfaces. As a first approach to realize this, surface designs with superimposed SMA and imprinted touch-sensitive zones were developed. In this way, the surfaces can react to temperature changes and to touch with different movement patterns.

Surface Behavior

The term behavior is often used in the context of active materials to refer to the functional aspects of such surfaces 11. In addition to their adaptability to changes in their environment, it is also the performative properties that characterize the behavior of such Materials. These are given special attention within Embedded Movement. Through the careful design of the movement and reaction patterns, in which the formal aspects of the surfaces, the deformation as well as speed and acceleration play an important role, it is investigated how human perception of these surfaces can be influenced. The first motion-studies within Embedded Movement seem organic/lifelike in the way they move. But, since they are far from being natural, the question rises, which attributes of the surfaces evoke this and what potentials this increased expressiveness holds in terms of communication between human and material.