2015, Lu, Xueyi, Deng, Junwen, Si, Wenping, Sun, Xiaolei, Liu, Xianghong, Liu, Bo, Liu, Lifeng, Oswald, Steffen, Baunack, Stefan, Grafe, Hans Joachim, Yan, Chenglin, Schmidt, Oliver G.

Trilayered Pd/MnOx/Pd nanomembranes are fabricated as the cathode catalysts for Li‐O2 batteries. The combination of Pd and MnOx facilitates the transport of electrons, lithium ions, and oxygen‐containing intermediates, thus effectively decomposing the discharge product Li2O2 and significantly lowering the charge overpotential and enhancing the power efficiency. This is promising for future environmentally friendly applications.

2021, Bandari, Vineeth Kumar, Schmidt, Oliver G.

The development of small machines, once envisioned by Feynman decades ago, has stimulated significant research in materials science, robotics, and computer science. Over the past years, the field of miniaturized robotics has rapidly expanded with many research groups contributing to the numerous challenges inherent to this field. Smart materials have played a particularly important role as they have imparted miniaturized robots with new functionalities and distinct capabilities. However, despite all efforts and many available soft materials and innovative technologies, a fully autonomous system-engineered miniaturized robot (SEMR) of any practical relevance has not been developed yet. In this review, the foundation of SEMRs is discussed and six main areas (structure, motion, sensing, actuation, energy, and intelligence) which require particular efforts to push the frontiers of SEMRs further are identified. During the past decade, miniaturized robotic research has mainly relied on simplicity in design, and fabrication. A careful examination of current SEMRs that are physically, mechanically, and electrically engineered shows that they fall short in many ways concerning miniaturization, full-scale integration, and self-sufficiency. Some of these issues have been identified in this review. Some are inevitably yet to be explored, thus, allowing to set the stage for the next generation of intelligent, and autonomously operating SEMRs.

2015, Karnaushenko, Daniil, Münzenrieder, Niko, Karnaushenko, Dmitriy D., Koch, Britta, Meyer, Anne K., Baunack, Stefan, Petti, Luisa, Tröster, Gerhard, Makarov, Denys, Schmidt, Oliver G.

Smart biomimetics, a unique class of devices combining the mechanical adaptivity of soft actuators with the imperceptibility of microelectronics, is introduced. Due to their inherent ability to self‐assemble, biomimetic microelectronics can firmly yet gently attach to an inorganic or biological tissue enabling enclosure of, for example, nervous fibers, or guide the growth of neuronal cells during regeneration.

2021, Chen, Yongpeng, Yin, Yin, Ma, Libo, Schmidt, Oliver G.

Optoplasmonic whispering-gallery-mode (WGM) microcavities, consisting of plasmonic nanostructures and optical microcavities, provide excellent platforms for exploring fundamental mechanisms as well as facilitating novel optoplasmonic applications. These integrated systems support hybrid modes with both subwavelength mode confinement and high-quality factor which do not exist in either pure optical WGM microcavities or plasmonic resonators. In this progress report, geometric designs and fabrication strategies of optoplasmonic microcavities, which efficiently bridge the interaction between resonant light and plasmonic resonances, are reviewed in detail. Three types of hybrid modes in the optoplasmonic microcavities, that is, surface-plasmon-polariton whispering-gallery modes, hybrid photon–plasmon whispering-gallery modes, and heterostructured metal–dielectric whispering-gallery modes, are considered. These modes are characterized by a largely enhanced evanescent field that is referred to as a plasmon-type field in hybrid whispering-gallery modes. Moreover, the coupling effect between localized surface plasmon resonances and whispering-gallery modes is summarized. The underlying coupling mechanisms and their influence on mode shifts, Q factor, mode splitting, and line shapes of the whispering-gallery modes are discussed. Applications based on optoplasmonic WGM microcavities including enhanced sensing, nanolasing, and free-space coupling are highlighted, followed by an outlook of the opportunities and challenges in developing large-scale on-chip integrated optoplasmonic systems.

2020, Li, Fei, Qu, Jiang, Li, Yang, Wang, Jinhui, Zhu, Minshen, Liu, Lixiang, Ge, Jin, Duan, Shengkai, Li, Tianming, Bandari, Vineeth Kumar, Huang, Ming, Zhu, Feng, Schmidt, Oliver G.

High performance, flexibility, safety, and robust integration for micro‐supercapacitors (MSCs) are of immense interest for the urgent demand for miniaturized, smart energy‐storage devices. However, repetitive photolithography processes in the fabrication of on‐chip electronic components including various photoresists, masks, and toxic etchants are often not well‐suited for industrial production. Here, a cost‐effective stamping strategy is developed for scalable and rapid preparation of graphene‐based planar MSCs. Combining stamps with desired shapes and highly conductive graphene inks, flexible MSCs with controlled structures are prepared on arbitrary substrates without any metal current collectors, additives, and polymer binders. The interdigitated MSC exhibits high areal capacitance up to 21.7 mF cm−2 at a current of 0.5 mA and a high power density of 6 mW cm−2 at an energy density of 5 µWh cm−2. Moreover, the MSCs show outstanding cycling performance and remarkable flexibility over 10 000 charge–discharge cycles and 300 bending cycles. In addition, the capacitance and output voltage of the MSCs are easily adjustable through interconnection with well‐defined arrangements. The efficient, rapid manufacturing of the graphene‐based interdigital MSCs with outstanding flexibility, shape diversity, and high areal capacitance shows great potential in wearable and portable electronics.

2015, Melzer, Michael, Karnaushenko, Daniil, Lin, Gungun, Baunack, Stefan, Makarov, Denys, Schmidt, Oliver G.

A novel fabrication method for stretchable magnetoresistive sensors is introduced, which allows the transfer of a complex microsensor systems prepared on common rigid donor substrates to prestretched elastomeric membranes in a single step. This direct transfer printing method boosts the fabrication potential of stretchable magnetoelectronics in terms of miniaturization and level of complexity, and provides strain‐invariant sensors up to 30% tensile deformation.

2021, Dong, Haiyun, Saggau, Christian Niclaas, Zhu, Minshen, Liang, Jie, Duan, Shengkai, Wang, Xiaoyu, Tang, Hongmei, Yin, Yin, Wang, Xiaoxia, Wang, Jiawei, Zhang, Chunhuan, Zhao, Yong Sheng, Ma, Libo, Schmidt, Oliver G.

Metal halide perovskites are promising materials for optoelectronic and photonic applications ranging from photovoltaics to laser devices. However, current perovskite devices are constrained to simple low-dimensional structures suffering from limited design freedom and holding up performance improvement and functionality upgrades. Here, a micro-origami technique is developed to program 3D perovskite microarchitectures toward a new type of microcavity laser. The design flexibility in 3D supports not only outstanding laser performance such as low threshold, tunable output, and high stability but also yields new functionalities like 3D confined mode lasing and directional emission in, for example, laser “array-in-array” systems. The results represent a significant step forward toward programmable microarchitectures that take perovskite optoelectronics and photonics into the 3D era. © 2021 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.

2020, Valligatla, Sreeramulu, Wang, Jiawei, Madani, Abbas, Naz, Ehsan Saei Ghareh, Hao, Qi, Saggau, Christian Niclaas, Yin, Yin, Ma, Libo, Schmidt, Oliver G.

3D photonic integrated circuits are expected to play a key role in future optoelectronics with efficient signal transfer between photonic layers. Here, the optical coupling of tubular microcavities, supporting resonances in a vertical plane, with planar microrings, accommodating in‐plane resonances, is explored. In such a 3D coupled composite system with largely mismatched cavity sizes, periodic mode splitting and resonant mode shifts are observed due to mode‐selective interactions. The axial direction of the microtube cavity provides additional design freedom for selective mode coupling, which is achieved by carefully adjusting the axial displacement between the microtube and the microring. The spectral anticrossing behavior is caused by strong coupling in this composite optical system and is excellently reproduced by numerical modeling. Interfacing tubular microcavities with planar microrings is a promising approach toward interlayer light transfer with added optical functionality in 3D photonic systems.

2014, Melzer, Michael, Mönch, Jens Ingolf, Makarov, Denys, Zabila, Yevhen, Bermúdez, Gilbert Santiago Cañón, Karnaushenko, Daniil, Baunack, Stefan, Bahr, Falk, Yan, Chenglin, Kaltenbrunner, Martin, Schmidt, Oliver G.

Highly flexible bismuth Hall sensors on polymeric foils are fabricated, and the key optimization steps that are required to boost their sensitivity to the bulk value are identified. The sensor can be bent around the wrist or positioned on the finger to realize an interactive pointing device for wearable electronics. Furthermore, this technology is of great interest for the rapidly developing market of ­eMobility, for optimization of eMotors and magnetic bearings.

2020, Zhu, Minshen, Wang, Xiaojie, Tang, Hongmei, Wang, Jiawei, Hao, Qi, Liu, Lixiang, Li, Yang, Zhang, Kai, Schmidt, Oliver G.

Hydrogels are widely used in flexible aqueous batteries due to their liquid-like ion transportation abilities and solid-like mechanical properties. Their potential applications in flexible and wearable electronics introduce a fundamental challenge: how to lower the freezing point of hydrogels to preserve these merits without sacrificing hydrogels' basic advantages in low cost and high safety. Moreover, zinc as an ideal anode in aqueous batteries suffers from low reversibility because of the formation of insulative byproducts, which is mainly caused by hydrogen evolution via extensive hydration of zinc ions. This, in principle, requires the suppression of hydration, which induces an undesirable increase in the freezing point of hydrogels. Here, it is demonstrated that cooperatively hydrated cations, zinc and lithium ions in hydrogels, are very effective in addressing the above challenges. This simple but unique hydrogel not only enables a 98% capacity retention upon cooling down to −20 °C from room temperature but also allows a near 100% capacity retention with >99.5% Coulombic efficiency over 500 cycles at −20 °C. In addition, the strengthened mechanical properties of the hydrogel under subzero temperatures result in excellent durability under various harsh deformations after the freezing process. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim