Tshikwand, Georgino Kaleng, M. Sc.

SoftFrac will revolutionise geometrically nonlinear fracture mechanics of soft materials (in short soft fracture) by capitalising on configurational mechanics, an unconventional continuum formulation that I helped shaping over the past decades. Mastering soft fracture will result in disruptive progress in designing the failure resilience of soft devices, i.e. soft robotics, stretchable electronics and tissue engineering applications. Soft materials are challenging since they can display moduli as low as only a few kPa, thus allowing for extremely large deformations. Geometrically linear fracture mechanics is well established, nevertheless not applicable for soft fracture given the over-restrictive assumptions of infinitesimal deformations. The appropriate geometrically nonlinear, finite deformation counterpart is, however, still in its infancy. By combining innovative data-driven/data-adaptive constitutive modelling with novel configurational-force-driven fracture onset and crack propagation, I will overcome the fundamental obstacles to date preventing significant progress in soft fracture. I propose three interwoven research Threads jointly addressing challenging theoretical, computational and experimental problems in soft fracture. The theoretical Thread establishes a new constitutive modelling ansatz for soft in/elastic materials, and develops the transformational configurational fracture approach. The computational Thread provides the associated novel algorithmic setting and delivers high-fidelity discretisation schemes to numerically follow crack propagation driven by accurately determined configurational forces. The experimental Thread generates and analyses comprehensive experimental data of soft materials and their geometrically nonlinear fracture for properly calibrating and validating the theoretical and computational developments. Ultimately, SoftFrac, for the first time, opens up new horizons for holistically exploring the nascent field soft fracture.

Programmable matter (PM) is a new emerging concept that is based on self-folding origami. Origami refers to a variety of techniques of transforming planar sheets into three-dimensional (3D) structures by folding, which has been introduced in science and engineering for, e.g., assembly and robotics. In principle, 2D pattern consisting of various materials can be transferred into any 3D pattern. The underlying idea of PM is to create a programmable material that can be shaped on demand reversibly and in different ways in order to perform multiple tasks. The initial planar system is composed of interconnected sections (tiles) that self-fold into a set of predetermined shapes using embedded actuators and magnetic latching. Thus, multiple 3D shapes with multiple functions can be realized. Current demonstrators use unidirectional actuators, consisting of a thin foil of the one-way shape memory alloy (SMA) Nitinol. Therefore, resetting to the initial planar state has to be performed manually before folding can be repeated. This concept has been demonstrated at the macro scale and the scalability of the current technology approach is limited to the size of tiles of several mm.
Here, we propose to transfer this concept into microtechnology by combining state-of-the art methods of micromachining, multifunctional materials as well as coupled simulation. As manual resetting will not be possible at the microscale, cooperative bi-directional actuation will be introduced, allowing for large bending angles up to 180°. Further challenges are the selective multistable latching and release of many tiles at the micro scale. Cooperation of both mechanisms will be needed to transform from flat shape to various specific 3D shapes and back to the flat shape by autonomous unfolding. Therefore, this project intends to develop a multistage multistable system of SMA and magnetic microactuators.  This new concept of re-programmable micro matter will enable formation and multistage adaptation of 3D shape at different length scales as well as reusability by reversible active unfolding. A monolithic fabrication route will be essential to realize many tiles with high integration density.
The development of the methods and tools for re-programmable micro matter requires an interdisciplinary approach. Therefore, this project combines the expertise from functional films (S. Fähler), microsystems (M. Kohl) and system simulation (F. Wendler).

Programmable matter (PM) is a new emerging concept that is based on self-folding origami. Origami refers to a variety of techniques of transforming planar sheets into three-dimensional (3D) structures by folding, which has been introduced in science and engineering for, e.g., assembly and robotics. In principle, 2D pattern consisting of various materials can be transferred into any 3D pattern. The underlying idea of PM is to create a programmable material that can be shaped on demand reversibly and in different ways in order to perform multiple tasks. The initial planar system is composed of interconnected sections (tiles) that self-fold into a set of predetermined shapes using embedded actuators and magnetic latching. Thus, multiple 3D shapes with multiple functions can be realized. Current demonstrators use unidirectional actuators, consisting of a thin foil of the one-way shape memory alloy (SMA) Nitinol. Therefore, resetting to the initial planar state has to be performed manually before folding can be repeated. This concept has been demonstrated at the macro scale and the scalability of the current technology approach is limited to the size of tiles of several mm. Here, we propose to transfer this concept into microtechnology by combining state-of-the art methods of micromachining, multifunctional materials as well as coupled simulation. As manual resetting will not be possible at the microscale, cooperative bi-directional actuation will be introduced, allowing for large bending angles up to 180°. Further challenges are the selective multistable latching and release of many tiles at the micro scale. Cooperation of both mechanisms will be needed to transform from flat shape to various specific 3D shapes and back to the flat shape by autonomous unfolding. Therefore, this project intends to develop a multistage multistable system of SMA and magnetic microactuators. This new concept of re-programmable micro matter will enable formation and multistage adaptation of 3D shape at different length scales as well as reusability by reversible active unfolding. A monolithic fabrication route will be essential to realize many tiles with high integration density.The development of the methods and tools for re-programmable micro matter requires an interdisciplinary approach. Therefore, this project combines the expertise from functional films (S. Fähler), microsystems (M. Kohl) and system simulation (F. Wendler).