November 2024
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Drawing inspiration from nature, soft materials are at the core of a transformation toward adaptive and responsive engineered systems, capable of conquering demanding terrain and safe when interacting with biological life. Despite recent advances in 3D printing of soft materials, researchers are still far from being able to print complex soft systems where a multitude of different components need to work together symbiotically. Closing this gap necessitates a platform that unites diverse materials into one synergetic process. Here, a multi‐material printing system is presented, combining gelatin‐based hydrogels with a new biodegradable support material. This organic ink maintains up to 60° overhang and is printable over gaps to structurally support the main biogel body, while triggered dissolution enables its selective removal and the formation of internal cavities. Therefore, the creation of vascular networks, tunable scaffolds, and embedded sensors within a single printing process becomes feasible. Furthermore, a perforation‐resistant, joint‐like vacuum actuator (VAc) is designed and 3D printed, capable of bending to angles up to 60° at fast response times down to 0.23 s. Combining these approaches in an efficient, streamlined fabrication process with biodegradable materials will unlock new sustainability dimensions for complex and durable soft systems.
![Electroluminescence quantum efficiency (ELQE)
a, Normalized electroluminescence (EL) spectra and b, the measured electroluminescence quantum efficiency (ELQE) values at different injection currents. The star indicates solar cell operating conditions, where the injection current equals the short-circuit current density under 1 sun illumination. c-f, Normalized measured (meas) and calculated (calc) EL photon flux and external quantum efficiency (EQE) for c, MAPbI3, d, Cs0.12MA0.88PbI3, e, MBA2MA6Pb7I22, f, MBA2(Cs0.12MA0.88)6Pb7I22 used for the calculation of the radiative limit of the open-circuit voltage VOCrad\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\rm{V}}}_{{\rm{OC}}}^{{\rm{rad}}}$$\end{document} following the procedure described in Supplementary Note 2. The convergence between the measured and calculated EQE and EL curves signifies a robust reciprocal relationship between the two. An Urbach tail fit was applied to the low energy part of the measured EQE below ~10⁻² quantum efficiency, resulting in the derived EQEPVfit\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{EQE}}_{{\rm{PV}}}^{{\rm{fit}}}$$\end{document} fit, capturing the exponential decay accurately. The respective Urbach energies as well as calculated open-circuit voltages are indicated in the plot.](https://www.researchgate.net/publication/379895728/figure/fig1/AS:11431281255876596@1719439557115/Electroluminescence-quantum-efficiency-ELQE-a-Normalized-electroluminescence-EL_Q320.jpg)
![The copper sensor on wood substrate used to analyze temperature dependency. a) Surface texture of beech veneer before and after sanding 0° to the fiber direction and 90° to the fiber direction b). The dashed lines in graphs (c–f) are linear fits of the measured data. c) Resistance of a copper trace on sanded beech as a function of length l for various widths w [0.25 mm (black); 0.50 mm (red); 0.75 mm (green); 1.00 mm (blue); 1.25 mm (turquoise); 1.50 mm (purple)] 0° to the fiber direction and for various widths w [1.00 mm (black); 1.25 mm (red); 1.50 mm (green); 1.75 mm (blue); 2.00 mm (turquoise); 2.25 mm (purple)] 90° to the fiber direction d). e) Conductance of a copper trace on sanded beech as a function of width w for various lengths l [5 mm (black); 10 mm (red); 15 mm (green); 20 mm (blue); 25 mm (turquoise); 30 mm (purple)] 0° to the fiber direction and 90° to the fiber direction f). Time‐dependent resistance measurement [black, thick line] of a copper sensor with meander structure and temperature measurement [blue, thin line] with a type K thermocouple. Measurements include one peak of 103 °C g), ten cycles with 103 °C maxima i), negative temperature of –20 °C k), and their respective temperature‐dependent resistance h, j, and l).](https://www.researchgate.net/publication/379032813/figure/fig3/AS:11431281260128235@1720842590445/The-copper-sensor-on-wood-substrate-used-to-analyze-temperature-dependency-a-Surface_Q320.jpg)
![The silver sensor on wood substrate used to analyze temperature dependency. a) Surface texture of sanded beech veneer with a screen‐printed silver trace 0° to the fiber direction. The dashed lines in graphs b,c) are linear fits of the measured data. b) Resistance of a silver trace on sanded beech as a function of length l for various widths w [0.30 mm (black); 0.50 mm (red); 1.00 mm (green)] 0° to the fiber direction. c) Conductance of a silver trace on sanded beech as a function of width w for various lengths l [2 cm (black); 4 cm (red); 8 cm (green); 12 cm (blue); 16 cm (turquoise); 20 cm (purple); 24 cm (yellow)] 0 ° to the fiber direction. Time‐dependent resistance measurement [black, thick line] of a silver sensor with meander structure and temperature measurement [blue, thin line] with a thermocouple type K. Measurements include one peak of 103 °C d), 10 cycles with 103 °C maxima f), negative temperature of –20 °C h) and their respective temperature‐dependent resistance e, g, and i).](https://www.researchgate.net/publication/379032813/figure/fig4/AS:11431281260128236@1720842590840/The-silver-sensor-on-wood-substrate-used-to-analyze-temperature-dependency-a-Surface_Q320.jpg)
![The copper sensor used to analyze the curing of varnish and the influence of humidity changes on the substrate. a) Hot press setup for applying varnish and performing in‐situ measurements. b) Ohmic conductance measured inside the hot press for various frequencies [10 000 Hz (black); 1000 Hz (red); 100 Hz (green)] and impedance at different times [0 min (yellow); 0.5 min (black); 5 min (red); 11 min (green); 14 min (blue); 17 min (turquoise); 20 min (purple)] d) at 150 °C c). e) Resistance increases over time without surface sealing and with varnish g) caused by swelling/shrinking of the wood due to changes in relative humidity at room temperature f, h). i) Photographs of wooden multimedia touchpad and measured signal amplitudes due to touches of varying force j).](https://www.researchgate.net/publication/379032813/figure/fig5/AS:11431281260145947@1720842591234/The-copper-sensor-used-to-analyze-the-curing-of-varnish-and-the-influence-of-humidity_Q320.jpg)
