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- ItemMicromotor-mediated sperm constrictions for improved swimming performance(Berlin ; Heidelberg : Springer, 2021) Striggow, Friedrich; Nadporozhskaia, Lidiia; Friedrich, Benjamin M.; Schmidt, Oliver G.; Medina-Sánchez, MarianaSperm-driven micromotors, consisting of a single sperm cell captured in a microcap, utilize the strong propulsion generated by the flagellar beat of motile spermatozoa for locomotion. It enables the movement of such micromotors in biological media, while being steered remotely by means of an external magnetic field. The substantial decrease in swimming speed, caused by the additional hydrodynamic load of the microcap, limits the applicability of sperm-based micromotors. Therefore, to improve the performance of such micromotors, we first investigate the effects of additional cargo on the flagellar beat of spermatozoa. We designed two different kinds of microcaps, which each result in different load responses of the flagellar beat. As an additional design feature, we constrain rotational degrees of freedom of the cell’s motion by modifying the inner cavity of the cap. Particularly, cell rolling is substantially reduced by tightly locking the sperm head inside the microcap. Likewise, cell yawing is decreased by aligning the micromotors under an external static magnetic field. The observed differences in swimming speed of different micromotors are not so much a direct consequence of hydrodynamic effects, but rather stem from changes in flagellar bending waves, hence are an indirect effect. Our work serves as proof-of-principle that the optimal design of microcaps is key for the development of efficient sperm-driven micromotors.
- ItemNano-biosupercapacitors enable autarkic sensor operation in blood([London] : Nature Publishing Group UK, 2021) Lee, Yeji; Bandari, Vineeth Kumar; Li, Zhe; Medina-Sánchez, Mariana; Maitz, Manfred F.; Karnaushenko, Daniil; Tsurkan, Mikhail V; Karnaushenko, Dmitriy D.; Schmidt, Oliver G.Today’s smallest energy storage devices for in-vivo applications are larger than 3 mm3 and lack the ability to continuously drive the complex functions of smart dust electronic and microrobotic systems. Here, we create a tubular biosupercapacitor occupying a mere volume of 1/1000 mm3 (=1 nanoliter), yet delivering up to 1.6 V in blood. The tubular geometry of this nano-biosupercapacitor provides efficient self-protection against external forces from pulsating blood or muscle contraction. Redox enzymes and living cells, naturally present in blood boost the performance of the device by 40% and help to solve the self-discharging problem persistently encountered by miniaturized supercapacitors. At full capacity, the nano-biosupercapacitors drive a complex integrated sensor system to measure the pH-value in blood. This demonstration opens up opportunities for next generation intravascular implants and microrobotic systems operating in hard-to-reach small spaces deep inside the human body.
- ItemFlexible MXene films for batteries and beyond(Hoboken, NJ : Wiley, 2022) Huang, Yang; Lu, Qiongqiong; Wu, Dianlun; Jiang, Yue; Liu, Zhenjie; Chen, Bin; Zhu, Minshen; Schmidt, Oliver G.MXenes add dozens of metallic conductors to the family of two-dimensional (2D) materials. A top-down synthesis approach removing A-layer atoms (e.g., Al, Si, and Ga) in MAX phases to produce 2D flakes attaches various surface terminations to MXenes. With these terminations, MXenes show tunable properties, promising a range of applications from energy storage devices to electronics, including sensors, transistors, and antennas. MXenes are also excellent building blocks to create flexible films used for flexible and wearable devices. This article summarizes the synthesis of MXene flakes and highlights aspects that need attention for flexible devices. Rather than listing the development of energy storage devices in detail, we focus on the main challenges of and solutions for constructing high-performance devices. Moreover, we show the applications of MXene films in electronics to call on designs to construct a complete system based on MXene with good flexibility, which consists of a power source, sensors, transistors, and wireless communications.
- ItemHuman spermbots for patient-representative 3D ovarian cancer cell treatment(Cambridge : RSC Publ., 2020) Xu, Haifeng; Medina-Sánchez, Mariana; Zhang, Wunan; Seaton, Melanie P. H.; Brison, Daniel R.; Edmondson, Richard J.; Taylor, Stephen S.; Nelson, Louisa; Zeng, Kang; Bagley, Steven; Ribeiro, Carla; Restrepo, Lina P.; Lucena, Elkin; Schmidt, Christine K.; Schmidt, Oliver G.Cellular micromotors are attractive for locally delivering high concentrations of drug, and targeting hard-to-reach disease sites such as cervical cancer and early ovarian cancer lesions by non-invasive means. Spermatozoa are highly efficient micromotors perfectly adapted to traveling up the female reproductive system. Indeed, bovine sperm-based micromotors have shown potential to carry drugs toward gynecological cancers. However, due to major differences in the molecular make-up of bovine and human sperm, a key translational bottleneck for bringing this technology closer to the clinic is to transfer this concept to human material. Here, we successfully load human sperm with Doxorubicin (DOX) and perform treatment of 3D cervical cancer and patient-representative ovarian cancer cell cultures, resulting in strong anticancer cell effects. Additionally, we define the subcellular localization of the chemotherapeutic drug within human sperm, using high-resolution optical microscopy. We also assess drug effects on sperm motility and viability over time, employing sperm samples from healthy donors as well as assisted reproduction patients. Finally, we demonstrate guidance and release of human drug-loaded sperm onto cancer tissues using magnetic microcaps, and show the sperm microcap loaded with a second anticancer drug, camptothecin (CPT), which unlike DOX is not suitable for directly loading into sperm due to its hydrophobic nature. This co-drug delivery approach opens up novel targeted combinatorial drug therapies for future applications. © 2020 The Royal Society of Chemistry.
- ItemIntegrated molecular diode as 10 MHz half-wave rectifier based on an organic nanostructure heterojunction([London] : Nature Publishing Group UK, 2020) Li, Tianming; Bandari, Vineeth Kumar; Hantusch, Martin; Xin, Jianhui; Kuhrt, Robert; Ravishankar, Rachappa; Xu, Longqian; Zhang, Jidong; Knupfer, Martin; Zhu, Feng; Yan, Donghang; Schmidt, Oliver G.Considerable efforts have been made to realize nanoscale diodes based on single molecules or molecular ensembles for implementing the concept of molecular electronics. However, so far, functional molecular diodes have only been demonstrated in the very low alternating current frequency regime, which is partially due to their extremely low conductance and the poor degree of device integration. Here, we report about fully integrated rectifiers with microtubular soft-contacts, which are based on a molecularly thin organic heterojunction and are able to convert alternating current with a frequency of up to 10 MHz. The unidirectional current behavior of our devices originates mainly from the intrinsically different surfaces of the bottom planar and top microtubular Au electrodes while the excellent high frequency response benefits from the charge accumulation in the phthalocyanine molecular heterojunction, which not only improves the charge injection but also increases the carrier density.
- ItemImperceptible Supercapacitors with High Area-Specific Capacitance(Weinheim : Wiley-VCH, 2021) Ge, Jin; Zhu, Minshen; Eisner, Eric; Yin, Yin; Dong, Haiyun; Karnaushenko, Dmitriy D.; Karnaushenko, Daniil; Zhu, Feng; Ma, Libo; Schmidt, Oliver G.Imperceptible electronics will make next-generation healthcare and biomedical systems thinner, lighter, and more flexible. While other components are thoroughly investigated, imperceptible energy storage devices lag behind because the decrease of thickness impairs the area-specific energy density. Imperceptible supercapacitors with high area-specific capacitance based on reduced graphene oxide/polyaniline (RGO/PANI) composite electrodes and polyvinyl alcohol (PVA)/H2SO4 gel electrolyte are reported. Two strategies to realize a supercapacitor with a total device thickness of 5 µm—including substrate, electrode, and electrolyte—and an area-specific capacitance of 36 mF cm−2 simultaneously are implemented. First, the void volume of the RGO/PANI electrodes through mechanical compression is reduced, which decreases the thickness by 83% while retaining 89% of the capacitance. Second, the PVA-to-H2SO4 mass ratio is decreased to 1:4.5, which improves the ion conductivity by 5000% compared to the commonly used PVA/H2SO4 gel. Both advantages enable a 2 µm-thick gel electrolyte for planar interdigital supercapacitors. The impressive electromechanical stability of the imperceptible supercapacitors by wrinkling the substrate to produce folds with radii of 6 µm or less is demonstrated. The supercapacitors will be meaningful energy storage modules for future self-powered imperceptible electronics.
- ItemAdvanced architecture designs towards high-performance 3D microbatteries(Amsterdam : Elsevier, 2021) Li, Yang; Qu, Jiang; Li, Fei; Qu, Zhe; Tang, Hongmei; Liu, Lixiang; Zhu, Minshen; Schmidt, Oliver G.Rechargeable microbatteries are important power supplies for microelectronic devices. Two essential targets for rechargeable microbatteries are high output energy and minimal footprint areas. In addition to the development of new high-performance electrode materials, the device configurations of microbatteries also play an important role in enhancing the output energy and miniaturizing the footprint area. To make a clear vision on the design principle of rechargeable microbatteries, we firstly summarize the typical configurations of microbatteries. The advantages of different configurations are thoroughly discussed from the aspects of fabrication technologies and material engineering. Towards the high energy output at a minimal footprint area, a revolutionary design for microbatteries is of great importance. In this perspective, we review the progress of fabricating microbatteries based on the rolled-up nanotechnology, a derivative origami technology. Finally, we discussed the challenges and perspectives in the device design and materials optimization.
- ItemIRONSperm: Sperm-templated soft magnetic microrobots(Washington, DC : American Association for the Advancement of Science, 2020) Magdanz, Veronika; Khalil, Islam S.M.; Simmchen, Juliane; Furtado, Guilherme P.; Mohanty, Sumit; Gebauer, Johannes; Xu, Haifeng; Klingner, Anke; Aziz, Azaam; Medina-Sánchez, Mariana; Schmidt, Oliver G.; Misra, SarthakWe develop biohybrid magnetic microrobots by electrostatic self-assembly of nonmotile sperm cells and magnetic nanoparticles. Incorporating a biological entity into microrobots entails many functional advantages beyond shape templating, such as the facile uptake of chemotherapeutic agents to achieve targeted drug delivery. We present a single-step electrostatic self-assembly technique to fabricate IRONSperms, soft magnetic microswimmers that emulate the motion of motile sperm cells. Our experiments and theoretical predictions show that the swimming speed of IRONSperms exceeds 0.2 body length/s (6.8 ± 4.1 µm/s) at an actuation frequency of 8 Hz and precision angle of 45°. We demonstrate that the nanoparticle coating increases the acoustic impedance of the sperm cells and enables localization of clusters of IRONSperm using ultrasound feedback. We also confirm the biocompatibility and drug loading ability of these microrobots, and their promise as biocompatible, controllable, and detectable biohybrid tools for in vivo targeted therapy.
- ItemRecent developments of stamped planar micro-supercapacitors: Materials, fabrication and perspectives(Amsterdam : Elsevier, 2021) Li, Fei; Li, Yang; Qu, Jiang; Wang, Jinhui; Bandari, Vineeth Kumar; Zhu, Feng; Schmidt, Oliver G.The rapid development of wearable and portable electronics has dramatically increased the application for miniaturized energy storage components. Stamping micro-supercapacitors (MSCs) with planar interdigital configurations are considered as a promising candidate to meet the requirements. In this review, recent progress of the different stamping materials and various stamping technologies are first discussed. The merits of each material, manufacturing process of each stamping method and the properties of stamping MSCs are scrutinized, respectively. Further insights on technical difficulties and scientific challenges are finally demonstrated, including the limited thickness of printed electrodes, poor overlay accuracy and printing resolution.
- ItemTargeted Sub-Attomole Cancer Biomarker Detection Based on Phase Singularity 2D Nanomaterial-Enhanced Plasmonic Biosensor(Berlin ; Heidelberg [u.a.] : Springer, 2021) Wang, Yuye; Zeng, Shuwen; Crunteanu, Aurelian; Xie, Zhenming; Humbert, Georges; Ma, Libo; Wei, Yuanyuan; Brunel, Aude; Bessette, Barbara; Orlianges, Jean-Christophe; Lalloué, Fabrice; Schmidt, Oliver G.; Yu, Nanfang; Ho, Ho-PuiDetection of small cancer biomarkers with low molecular weight and a low concentration range has always been challenging yet urgent in many clinical applications such as diagnosing early-stage cancer, monitoring treatment and detecting relapse. Here, a highly enhanced plasmonic biosensor that can overcome this challenge is developed using atomically thin two-dimensional phase change nanomaterial. By precisely engineering the configuration with atomically thin materials, the phase singularity has been successfully achieved with a significantly enhanced lateral position shift effect. Based on our knowledge, it is the first experimental demonstration of a lateral position signal change > 340 μm at a sensing interface from all optical techniques. With this enhanced plasmonic effect, the detection limit has been experimentally demonstrated to be 10–15 mol L−1 for TNF-α cancer marker, which has been found in various human diseases including inflammatory diseases and different kinds of cancer. The as-reported novel integration of atomically thin Ge2Sb2Te5 with plasmonic substrate, which results in a phase singularity and thus a giant lateral position shift, enables the detection of cancer markers with low molecular weight at femtomolar level. These results will definitely hold promising potential in biomedical application and clinical diagnostics.