Programmable matter is a technical material whose properties can be changed in a programmed (or predetermined) way. Compared to conventional manufacturing methods, 4D printing can create more advanced and complicated programmable materials. Many exotic properties, including negative refractive index and nonlinear second harmonic generation, can be realized using metamaterials.
The properties of metamaterials can be tuned by engineering the design of unit cells or their arrangement. In the case of adding tunability to metamaterials, tunable metamaterials that can exhibit different properties to stimuli can be considered programmable matter. In this thesis, I will propose methods to realize programmable matter through printing technologies, including 4D printed structures and silver nano-ink printing.
Therefore, these bistable structures can be useful for simplified motion control in actuators or for mechanical switches. Additionally, SMPs can be reused multiple times for thermal actuation by simply repeating thermomechanical programming.
Introduction
- Programmble matter
- Hydrogel
- Shape memory polymer
- Liquid crystal elastomer
- Bilayer structures
- Overview of bilayer structures
- Multistable structures
- Strained layer
- Compliant mechanism
- Mechanical metamaterials
- Outline of the thesis
- Introduction
- Results and Discussion
- Elastic-potential energy diagram for bistable components
- Twisting bistable components
- Rotational bistable components
- Tunable bistable structures with SMP elements
- Tunable rotational bistable components
- Conclusions
The FE simulation results are in good agreement with the experimental results of all three cases.38 Figure 1.9 (a) Two steady states of the Venus flytrap. 11 Figure 1.10 Bistable structures of the prestressed layer. a) Printed form of cylindrical shells with radii from 5 mm to 10 mm after removal from the build plate. Due to the symmetrical shape of the two stable states, the energy diagram is also symmetrically shaped.43 Figure 1.12 Bistable conditions of a beam with a fixed clamped boundary condition.
On the other hand, the symmetric form of the energy diagram is generated in the Pinned-Pinned case.44 Figure 1.14 Mechanical metamaterials with bistability. a) Geometric parameters of the unit cell which is composed of 4 triangular structures. 48 Figure 1.16 Pre-printed 4D-printed bistable saddle structure. a) Morphing behavior of a pre-printed 4D bistable saddle structure. The bottom images are captures of the bistable structure as it transforms from a bistable structure to a monostable structure.
Inset: images of the ball joint for torsional components (left) and the pin joint for rotating components (right). 62 Figure 2.3 Dynamic mechanical analysis (DMA) was used to measure the temperature-dependent (a) modulus and (b) tanδ values.
Multistable thermal actuators via multi-material 4D printing
- Introduction
- Results and discussion
- General concepts of 4D printed bistable rotational structure
- Thermal actuation of 4D printed bistable structure
- Analysis of 4D printed bistable structure
- Ambient demonstration of fabricated thermal switch
- Conclusions
- Introduction
- Results and Discussion
- Selective light absorption of colored SMPs
- Analysis of bending behavior of light-activated structure
- Conclusions
The seconds in the figure are the time elapsed after the structure was immersed in water..78 Figure 3.5 (a) DMA measurement of shape memory power in the constraint-recovery condition and (b) the measurement configuration. We find that structural deformation at room temperature also induces shape memory recovery power at high temperature..78 Figure 3.6 Snapshots for structural analysis of bistable structure. left) same shape as DMA measurement, (right). Dotted line indicates normal directional component of shape memory force..81 Figure 3.7 (a) Activation time for different rubbery beam thicknesses.
Fbarrier..82 Figure 3.8 (a) Images of a quadristable structure that has four stable states. b) Thermal activation tests at 45 ºC and 75 ºC. It is possible to achieve more diverse thermal activation behavior by controlling design parameters..84 Figure 3.9 Design of a quadristable structure. Thermomechanical programming and bending behavior (the dashed line in the figure is an eye guide)..90 Figure 4.2 Selective heating of colored SMPs. a) and (b) The reflection, transmission and absorption spectra of the blue and yellow SMP sheets, respectively, in the visible wavelength range.
97 Figure 4.6 Snapshots from heat transfer simulation..98 Figure 4.7 Storage moduli and loss tangents of the SMPs and the matrix material. The maximum recovery ratio for SMP was approx. 92%..101 Figure 4.9 Multicolored hinged structure for multistep activation.
Tunable resonance and phase vortices in kirigami Fano-resonant
Introduction
Such IoT technologies require widespread antennas and sensors; they must be cheap enough to be widely deployed while maintaining high functionality. Electromagnetic metamaterials enable ultimate control of electromagnetic waves to unprecedented levels and can therefore be very useful for various microwave antennas and components160-166. In addition, resonant field enhancement in metamaterials makes them ideal for various sensing applications via electromagnetic detection 167 , 168 .
Here, we report a new approach based on kirigami Fano-resonant metamaterials that could be useful for various antennas and sensors. The resulting asymmetric resonance spectrum can be tuned by controlling the structural asymmetry of the metamaterial unit cell. In addition to sharp spectral features, Fano-resonant metamaterials exhibit strong field enhancement, which could be very useful for sensor devices.
The printed paper is then cut and folded line by line so that a step height between adjacent unit cells can be created and easily matched. By varying the step height between adjacent cells, significant spectral tuning and resonant switching is achieved in kirigami metamaterials. We explain our experimental observations based on the interaction energy between electric/magnetic dipoles in adjacent unit cells.
The large spectral shift of the highly asymmetric Fano line shape also allows significant control of the radiation direction, from strong reflection to strong transmission. Moreover, we observe a phase singularity at the zero amplitude position of the Fano resonance spectrum. Depending on the step height, the transmission phase changes from a negative to a positive slope and vice versa.
We explain these changes in terms of phase vortex; a few phase vortices appear in parameter space. By reducing the structure asymmetry in the metamaterial unit cell, these two phase vortices come closer. These drastic phase changes around singularity points can be very useful for various applications, such as optical sensing and wavefront engineering.
Experimental section
- Fabrication of kirigami metamaterials
- Microwave measurements
- Numerical electromagnetic simulations
In the case of the horizontal section, the line width change is also clearly visible; it initially decreases and then increases. As shown in Figure 5.5 (a), the vertical and horizontal cuts in our kirigami metamaterial create different configurations for dipolar coupling between neighboring unit cells. In the horizontal section, longitudinally coupled electric dipoles are separated in the y-direction in space.
In both vertical and horizontal sections, magnetic dipoles are transversely coupled because all magnetic dipoles are oriented out of plane (ie in the z direction). However, we see that in the case of the horizontal section, the quasi-static analysis (solid curves) deviates from the retarded simulation and experiment, especially at larger step heights (H > 4 mm). On the other hand, it remains similar to the retarded data even for larger step heights in the case of the vertical section.
In the case of the vertical section, magnetic and electric dipoles remain dominant contributions at the Fano resonance frequency, even for larger step heights. However, in the case of the horizontal section, we find that the electric quadrupole moment also rises as the step height increases in addition to magnetic and electric dipoles. However, electric dipoles are coupled transversely in the x-direction, while they are coupled longitudinally in the y-direction.
In the vertical section, the electric dipoles connected transversely in the x direction are separated in space. In the horizontal section, the longitudinally coupled electric dipoles in the y direction are separated in space. In the vertical cut, all phase singularities show negative slopes, but we find another interesting behavior for the horizontal cut.
In the case of vertical shear, the transmission coefficient approaches the origin (i.e., the magnitude |S21| becomes close to zero). On the other hand, in the case of horizontal shear, the complex transmission coefficient surrounds the origin, although its magnitude remains very small around the origin. The large spectral shift of the highly asymmetric Fano line shape in our kirigami metamaterials enables this drastic change in directional response.
Results and Deiscussion
- Sample design and preparation
- Measurement setup & Transmission spectra of flat structures
- Transmission spectra of kirigami Fano-metamaterials
- Analysis of kirigami Fano-resonant metamaterials
- Phase vortices of kirigami Fano-resonant metamaterials
Conclusions
In this dissertation I introduced 4D printing and programmable metamaterials as design and realization methods for programmable matter. 4D printing can be realized by 3D printing smart materials such as hydrogel, SMP and LCE. Exploiting the benefits of using multistable structures in 4D printing research, I demonstrated 3D printed tunable bistable structures and 4D printed thermal actuators.
Using light control as a stimulus for a 4D printed structure, I demonstrated multi-color 4D printing of SMP composites and remote actuation by color-dependent selective heating. By extensively investigating the behavior of SMP shape memory with temperature variance and structural properties of materials, I was able to explain the bending behavior of light-activated 4D printed structures under different programming loads. In this dissertation, I investigated 4D printed structures that can alleviate the problems of conventional 4D printing studies.
This dissertation offers new perspectives and can potentially lead to new advances in the fields of 4D printing research. H.; Zhu, W.; Victorine, G.; Lawrence, N.; Chen, S., 3D printing of functional biomedical microdevices via light and extrusion-based approaches. Zhang, M.; Wang, Y.; Jian, M.; Wang, C.; Liang, X.; Niu, J.; Zhang, Y., Spontaneous alignment of graphene oxide in hydrogel during 3D printing for multi-stimulus actuation.
Yan, C., 4D printing self-sensing and temperature self-sensing integrated sensor-actuator with bio-inspired gradient apertures. Chen, Z.; Wang, R., Mechanically robust and UV-curable shape memory polymers for digital light processing-based 4D printing. Zarek, M.; Layani, M.; Cooperstein, I; Sachyani, E.; Cohn, D.; Magdassi, S., 3D printing of shape memory polymers for flexible electronic devices.
A., 3D printable and reconfigurable liquid crystal elastomers with light-induced shape memory via dynamic bond exchange. Ji, Z.; Yan, C.; Yu, B.; Wang, X.; Zhou, F., Multimaterials 3D printing for free assembly production of magnetic driving soft actuator. K; Liu, Y., Multi-stage responsive 4D printed smart structure by varying geometric thickness of shape memory polymer.
