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Shaping soft and conductive materials into sophisticated architectures through 3D printing is driving innovation in myriad applications, such as robotic counterparts that emulate the synergic functions of biological systems. Although recently developed multi‐material 3D printing has enabled on‐demand creation of intricate artificial counterparts from a wide range of functional viscoelastic materials. However, directly achieving complementary functionalities in one ink design remains largely unexplored, given the issues of printability and synergy among ink components. In this study, an easily accessible and self‐regulating tricomponent ionogel‐based ink design to address these challenges is reported. The resultant 3D printed objects, based on the same component but with varying ratios of ink formulations, exhibit distinct yet complementary properties. For example, their Young's modulus can differ by three orders of magnitude, and some structures are rigid while others are ductile and viscous. A theoretical model is also employed for predicting and controlling the printing resolution. By integrating complementary functionalities, one further demonstrates a representative bioinspired prototype of spiderweb, which mimics the sophisticated structure and multiple functions of a natural spiderweb, even working and camouflaging underwater. This ink design strategy greatly extends the material choice and can provide valuable guidance in constructing diverse artificial systems by 3D printing. [ABSTRACT FROM AUTHOR]

Abstract Shaping soft and conductive materials into sophisticated architectures through 3D printing is driving innovation in myriad applications, such as robotic counterparts that emulate the synergic functions of biological systems. Although recently developed multi‐material 3D printing has enabled on‐demand creation of intricate artificial counterparts from a wide range of functional viscoelastic materials. However, directly achieving complementary functionalities in one ink design remains largely unexplored, given the issues of printability and synergy among ink components. In this study, an easily accessible and self‐regulating tricomponent ionogel‐based ink design to address these challenges is reported. The resultant 3D printed objects, based on the same component but with varying ratios of ink formulations, exhibit distinct yet complementary properties. For example, their Young's modulus can differ by three orders of magnitude, and some structures are rigid while others are ductile and viscous. A theoretical model is also employed for predicting and controlling the printing resolution. By integrating complementary functionalities, one further demonstrates a representative bioinspired prototype of spiderweb, which mimics the sophisticated structure and multiple functions of a natural spiderweb, even working and camouflaging underwater. This ink design strategy greatly extends the material choice and can provide valuable guidance in constructing diverse artificial systems by 3D printing.

This research is focused on the design and realization of high-performance high-power variable phase shifters in groove gap waveguide technology. Specifically, it is shown that the unique characteristic of groove gap waveguides, which is its proper operation without the need for electrical connection between the top and bottom sections of the waveguide, can be used to design mechanically tunable devices. Using the proposed method, a mechanically tunable cavity resonator and phase shifters with a wide range of achievable phase shifts are presented. To validate the concept, a phase shifter with 540 degrees relative phase shift at 15 GHz is designed, fabricated, and measured. Moreover, a multi-layer version of the proposed phase shifter with stationary feed ports and improved performance is presented.

We leverage the crucial hyperelastic properties of a multifunctional structured surface to optimize the reconfigurability of the electromagnetic transmission under large nonlinear mechanical deformations. This multiphysics, multifunctional, hyperelastic structured surface (HSS) offers two simultaneous intriguing functionalities; tunability and switchability. It is made of copper resonators and a Polydimethylsiloxane (PDMS) substrate, which is one of the most favorable deformable substrates due to its hyperelastic behavior. The proposed HSS is fabricated via an original cost-effective technique and the multiphysics functionalities are captured in both experimental tests and numerical simulations. Leveraging the hyperelastic behavior, we demonstrate up to 8% percent shift in the resonance frequency in the GHz range, for average applied mechanical strains of around 17%. The hyperelastic deformations can continuously increase/decrease the magnitude of the scattering parameter S21 in the frequency range of 10.9 GHz to 11.8 GHz by more than 40 dB, changing from being largely transparent to opaque and vice versa. The potential of hyperelastic behavior to account for the multifunctionality of the HSS is validated experimentally. [ABSTRACT FROM AUTHOR]

We leverage the crucial hyperelastic properties of a multifunctional structured surface to optimize the reconfigurability of the electromagnetic transmission under large nonlinear mechanical deformations. This multiphysics, multifunctional, hyperelastic structured surface (HSS) offers two simultaneous intriguing functionalities; tunability and switchability. It is made of copper resonators and a Polydimethylsiloxane (PDMS) substrate, which is one of the most favorable deformable substrates due to its hyperelastic behavior. The proposed HSS is fabricated via an original cost-effective technique and the multiphysics functionalities are captured in both experimental tests and numerical simulations. Leveraging the hyperelastic behavior, we demonstrate up to 8% percent shift in the resonance frequency in the GHz range, for average applied mechanical strains of around 17%. The hyperelastic deformations can continuously increase/decrease the magnitude of the scattering parameter S21 in the frequency range of 10.9 GHz to 11.8 GHz by more than 40 dB, changing from being largely transparent to opaque and vice versa. The potential of hyperelastic behavior to account for the multifunctionality of the HSS is validated experimentally.

Hydrogels with good biocompatibility, proper degradation rates, and tissue-matched elasticity are widely used in tissue engineering, regenerative medicine, and drug delivery. In this study, enzymatically crosslinked biocompatible hydrogels were successfully developed using silk fibroin (SF) and pullulan (PL) under physiological conditions in the presence of both horseradish peroxidase and hydrogen peroxide. A series of properties of the hydrogels including gelation time, equilibrium swelling, enzyme degradation, morphology, rheological property, and compression modulus of SF/PL hydrogels were studied by varying the concentration of PL. The results showed that the SF/PL hydrogels had applicable gel-forming rate (ranging from 12 to 60 min), tunable compressive strength (ranging from 7 to 71 kPa) and shear mechanical properties (ranging from 200 to 1470 Pa). The properties of the SF/PL hydrogels were easily modulated by changing the concentration of PL. The compressive modulus of the SF + 20%PL hydrogels was 71.4 ± 9.3 kPa, which was in the range of that of musculoskeletal system. In addition, the rabbit bone marrow-derived mesenchymal stem cells were encapsulated in SF/PL hydrogels for 7 days, and cell viability and morphology were observed. Live/dead staining assay demonstrated that the hydrogel system possessed good cytocompatibility. These features support that SF/PL hydrogels have a potential as cell delivery scaffold in musculoskeletal tissue engineering. [ABSTRACT FROM AUTHOR]

A composite with high visible light transmittance, mechanically tunable refractive index (RI) and rubber-like mechanical properties, based on poly(dimethylsiloxane) (PDMS) and barium titanate nanoparticles (BT) was prepared on three steps. First, BT nanoparticles were obtained by high-energy milling. Second, the nanoparticles were embedded in PDMS by in-situ polymerization; the BT content was varied up to 1.0 wt% (0.17 vol%). Finally, ∼0.5 mm membranes were prepared by solvent casting. The effect of the BT concentration was examined. Powder XRD and Raman spectroscopy revealed a tetragonal crystal structure for the nanoparticles. SEM images confirmed a mean particle size of ∼64 nm and together with EDX mappings showed a moderate dispersion of the nanoparticles in some membranes, whereas other exhibited agglomerates at the surface. The normal transmittance of the membranes was measured with a spectroscopic ellipsometer while they were stretched in-situ at different percentages. The RI variations as a function of strain were calculated from the transmittance spectra. The results exhibit surprising variations in the RI, up to ∼5 times higher than those associated to PDMS alone, implying that the presence of BT significantly influences the optical response of the PDMS when stretched. However, the response is neither linear nor well understood; further studies must be performed to clarify this new interaction. [ABSTRACT FROM AUTHOR]

In this work, various pyrromethene dyes were doped into elastic films of polydimethylsiloxane (PDMS) as active layers of organic VCSELs and the laser properties of such PDMS-based VCSELs were systematically investigated. Mechanically tunable laser emission with high slope efficiencies, low threshold and wide tuning range were obtained. By uploading various stress or changing distributed-Bragg reflector (DBR) mirrors, single mode laser emission could be tuned from ∼590 to 690 nm, indicating their potential applications as cost-effective coherent sources on bio-chips. Under the pump energy 10 times higher than the threshold, the laser emission of organic VCSELs remained at its initial level after 1.2 × 10 5 pulses and a fast self-recovery process on the laser output energy with the elapse of aging time was observed. The differences between the self-recovery rates of various pyrromethene dyes were also discussed. [ABSTRACT FROM AUTHOR]

Mechanical tuning of defect modes in a polymer-based one-dimensional photonic crystal was demonstrated for the terahertz (THz) spectral range. A sharp defect mode in the photonic bandgap was achieved by symmetrically enclosing a defect layer with two identical pairs of alternating compact and low-density layers. By adjusting the thickness of the defect layer, the spectral position of the defect mode within the photonic bandgap was easily controlled. Normal incidence transmission spectroscopy in a spectral range from 82 to 125 GHz was used to determine the THz spectral response for different defect layer thicknesses. The transmission data were analyzed using stratified optical layer model calculations. Spectral shift of the center frequency of the narrow transmission peak within a distinct photonic bandgap was observed in the experimental transmission spectra. The shift was achieved by mechanical tuning of the defect layer thickness. A good agreement between the relevant model parameters and the corresponding design parameters was found. [ABSTRACT FROM AUTHOR]

Composite gratings play important roles in modern information technology. However, such gratings are generally based on the same structural pattern with limited types, and their structural parameters are difficult to tune, which greatly limit their application. A mechanically tunable composite grating in bilayer film, which orthogonally couples a sinusoidal phase grating and a rectangular phase grating, is developed here. The structural parameters of the grating can be well tuned by mechanically stretching or releasing the grating in the uniaxial direction. Naturally, this property allows tunable light manipulation: that is, a single incident laser beam can be split into a 2D diffraction beams array, and the intensity and propagation angle of each diffraction beam can be precisely controlled via mechanical manipulation of the grating. A theoretical model based on scalar diffraction theory that can quantitatively describe and accurately predict this light manipulation is further established. In addition, after treatment with an electron beam, the tunable structures can be immobilized, which enables the storage of information in the bilayer film. This work may open up new pathways for composite grating fabrication and further extend the applications of composite gratings in diverse fields. A composite grating orthogonally coupling a sinusoidal and a rectangular phase grating is created in a bilayer film. This pattern can be well tuned under mechanical manipulation, and it allows tunable light manipulation behavior. Under additional irradiation treatment, the tunable pattern can be immobilized, which allows one to store information into this bilayer film as well as to prepare a rigid grating on a compliant substrate. [ABSTRACT FROM AUTHOR]

Multi-material 3D printing with several mechanically distinct materials at once has expanded the potential applications for additive manufacturing technology. Fewer material options exist, however, for additive systems that employ vat photopolymerization (such as stereolithography, SLA, and digital light projection, DLP, 3D printers), which are more commonly used for advanced engineering prototypes and manufacturing. Those material selections that do exist are limited in their capacity for fusion due to disparate chemical and physical properties, limiting the potential mechanical range for multi-material printed composites. Here, we present an ethylene glycol phenyl ether acrylate (EGPEA)-based formulation for a polymer resin yielding a range of elastic moduli between 0.6 MPa and 33 MPa simply by altering the ratio of monomer and crosslinker feedstocks in the formulation. This simple chemistry is also well suited to form seamless adhesions between mechanically dissimilar formulations, making it a promising candidate for multi-material DLP 3D printing. Preliminary tests with these polymer formulations indicate that variability due to molecular differences between hard and soft formulations is near net shape and less than 3% of the prescribed dimensions, comparable to existing commercial DLP and SLA resins, with unique advantages of a wide range of elastomer stiffness and seamless fusion for 3D printing of structurally detailed and mechanically heterogeneous composites.