Materials and Methods for Sustainable Soft Devices 

Martin Kaltenbrunner*,#  

* Department of Soft Matter Physics, Johannes Kepler University Linz, Altenbergerstr. 69, 4040  

Linz, Austria (martin.kaltenbrunner@jku.at) 

# LIT Soft Materials Lab, Johannes Kepler University Linz, Altenbergerstr. 69, 4040 Linz,  

Austria (martin.kaltenbrunner@jku.at) 

Abstract 

Soft devices provide unique opportunities in our quest for a more sustainable future. Among the  key issues to overcome are the search for high performance green materials, end-of-lifetime  considerations in complex (soft) systems, and their energy efficiency.  

This talk aims at suggesting solutions for some of these grand challenges. We introduce  bioderived materials and fabrication methods for soft systems that biodegrade, yet are of high  resilience. Based on highly stretchable biogels and degradable elastomers, our forms of soft  electronics and robots are designed for prolonged operation in ambient conditions without fatigue,  but fully degrade after use through biological triggers. Electronic skins provide sensory feedback,  while stretchable and biodegradable batteries enable autonomous operation. 3D printing of  biodegradable hydrogels enables omnidirectional soft robots with multifaceted optical sensing  abilities. Going beyond, we introduce a systematically-determined compatible materials systems  for the creation of fully biodegradable, high-performance electrohydraulic soft actuators. These  embodiments reliably operate up to high electric fields, show performance comparable to nonbiodegradable counterparts, and survive over 100,000 actuation cycles. We elucidate their  fundamental operating principles and provide materials combinations that enable power-efficient electrohydraulic actuators void of detrimental interfacial charging. Pushing the boundaries of  sustainable electronics furhter, we demonstrate a concept for growth and processing of fungal  mycelium skins as biodegradable substrate material. Mycelium-based batteries with capacities as  high as ~3.8 mAh cm−2 allow to power autonomous sensing devices including a Bluetooth  module and humidity and proximity sensors, all integrated onto mycelium flexible circuit boards. 

References 

[1] M. Baumgartner, F. Hartmann, M. Drack, D. Preninger, D. Wirthl, R. Gerstmayr, L. Lehner,  G. Mao, R. Pruckner, S. Demchyshyn, L. Reiter, M. Strobel, T. Stockinger, D. Schiller, S. Kimeswenger, F. Greibich, G. Buchberger, E. Bradt, S. Hild, S. Bauer, M. Kaltenbrunner,  “Resilient yet entirely degradable gelatin-based biogels for soft robots and electronics”,  Nature Materials 19 (10), 1102-1109 (2020) 

[2] A. Heiden, D. Preninger, L. Lehner, M. Baumgartner, M. Drack, E. Woritzka, D. Schiller,  R. Gerstmayr, F. Hartmann, M. Kaltenbrunner, “3D printing of resilient biogels for  omnidirectional and exteroceptive soft actuators”, Science Robotics 63, 7 (2022) 

[3] E. H. Rumley, D. Preninger, A. S. Shomron, P. Rothemund, F. Hartmann, M. Baumgartner,  N. Kellaris, A. Stojanovic, Z. Yoder, B. Karrer, C. Keplinger, M. Kaltenbrunner, “Biodegradable electrohydraulic actuators for sustainable soft robots”, Science Advances 9,  eadf5551 (2023)

[4] I-D. Sîrbu, D. Preninger, D. Danninger, L. Penkner, R. Schwödiauer, G. Moretti, N. Arnold,  M. Fontana, M. Kaltenbrunner, “Electrostatic actuators with constant force at low power loss  using matched dielectrics”, Nature Electronics, (2023) 

[5] D. Danninger, R. Pruckner, L. Holzinger, R. Koeppe, M. Kaltenbrunner, “MycelioTronics:  Fungal mycelium skin for sustainable electronics”, Science Advances 8 (45), eadd7118 (2022);