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Traditional robotic vehicle control algorithms, implemented on digital devices with firmware, result in high power consumption and system complexity. Advanced control systems based on different device physics are essential for the advancement of sophisticated robotic vehicles and miniature mobile robots. Here, we present a nanoelectronics-enabled analog control system mimicking conventional controllers’ dynamic responses for real-time robotic controls, substantially reducing training cost, power consumption, and footprint. This system uses a reservoir computing network with interconnected memristive channels made from layered semiconductors. The network’s nonlinear switching and short-term memory characteristics effectively map input sensory signals to high-dimensional data spaces, enabling the generation of motor control signals with a simply trained readout layer. This approach minimizes software and analog-to-digital conversions, enhancing energy and resource efficiency. We demonstrate this system with two control tasks: rover target tracking and drone lever balancing, achieving similar performance to traditional controllers with ~10-microwatt power consumption. This work paves the way for ultralow-power edge computing in miniature robotic systems. 

2D-layered materials (e.g., graphene and transition metal dichalcogenides) have attracted huge attention due to their unique mechanical and electrical properties. Emerging research efforts, which seek to combine device characterization and high-resolution electron micrography analysis for 2D-layered device features, demand nano/microlithographic techniques capable of producing ordered 2D material patterns on ultrathin membranes with nanoscale thicknesses. However, such membranes are so fragile that most conventional lithographic techniques can be hardly performed on them to generate 2D material patterns. Our previous works have demonstrated that the rubbing-induced site-selective (RISS) deposition method can produce arbitrary 2D semiconductor (e.g., MoS2 and Bi2Se3) patterns on regular device substrates. This fabrication route prevents the vulnerable 2D-layered structures from the detrimental damage introduced by plasma etching and resist-based lithography processes. In this work, we explore the applicability of RISS for directly producing 2D material patterns on nanomembranes. Specifically, this work shows that a polymeric interfacing layer on the rubbing template features, which can effectively prevent stress concentration during the rubbing process, is crucial to successful implementation of RISS processes on nanomembranes. Furthermore, we carried out the mechanics simulation of the Von Mises stress and pressure distribution on the RISS-processed membrane to identify the optimal rubbing load, which can generate sufficient triboelectric charge for material deposition but no damage to the membrane. Using this approach, we have successfully demonstrated the deposition of Bi2Se3 patterns on 25 nm SiOx nanomembranes and high-resolution transmission electron micrography characterization of the crystallographic structures. 

Despite the unique advantages of the memristive switching devices based on two-dimensional (2D) transition metal dichalcogenides, scalable growth technologies of such 2D materials and wafer-level fabrication remain challenging. In this work, we present the gold-assisted large-area physical vapor deposition (PVD) growth of Bi2Se3 features for the scalable fabrication of 2D-material-based crossbar arrays of memristor devices. This work indicates that gold layers, prepatterned by photolithography processes, can catalyze PVD growth of few-layer Bi2Se3 with 100-folds larger crystal grain size in comparison with that grown on bare Si/SiO2 substrates. We also present a fluid-guided growth strategy to improve growth selectivity of Bi2Se3 on Au layers. Through the experimental and computational analyses, we identify two key processing parameters, i.e., the distance between Bi2Se3 powder and the target substrate and the distance between the leading edges of the substrate and the substrate holder with a hollow interior, which plays a critical role in realizing large-scale growth. By optimizing these growth parameters, we have successfully demonstrated cm-scale highly-selective Bi2Se3 growth on crossbar-arrayed structures with an in-lab yield of 86%. The whole process is etch- and plasma-free, substantially minimizing the damage to the crystal structure and also preventing the formation of rough 2D-material surfaces. Furthermore, we also preliminarily demonstrated memristive devices, which exhibit reproducible resistance switching characteristics (over 50 cycles) and a retention time of up to 106 s. This work provides a useful guideline for the scalable fabrication of vertically arranged crossbar arrays of 2D-material-based memristive devices, which is critical to the implementation of such devices for practical neuromorphic applications. 

Herein we report the assessment of the effects of shockwave (SW) impacts on adult rat hippocampal progenitor cell (AHPC) neurospheres (NSs), which are used as in vitro brain models, for enhancing our understanding of the mechanisms of traumatic brain injury (TBI). The assessment has been achieved by using culture dishes and a new microchip. The microchip allows the chemicals released from the brain models cultured inside the cell culture chamber under SW impacts to diffuse to the nano sensors in adjacent sensor chambers through built-in diffusion barriers, which are used to prevent the cells from entering the sensor chambers, thereby mitigating the biofouling issues of the sensor surface. Experiments showed the negative impact of the SW on the viability, proliferation, and differentiation of the cells within the NSs. A qPCR gene expression analysis was performed and appeared to confirm some of the immunocytochemistry (ICC) results. Finally, we demonstrated that the microchip can be used to monitor lactate dehydrogenase (LDH) released from the AHPC-NSs subjected to SW impacts. As expected, LDH levels changed when AHPC-NSs were injured by SW impacts, verifying this chip can be used for assessing the degrees of injuries of AHPC-NSs by monitoring LDH levels. Taken together, these results suggest the feasibility of using the chip to better understand the interactions between SW impacts and in vitro brain models, paving a way for potentially establishing in vitro TBI models on a chip. 

Memristors based on 2D semiconductors such as MoS2 and its derivative materials exhibit analog switching behaviors capable of emulating some synaptic functions, including short-term plasticity, long-term potentiation, and spike-time-dependent-plasticity. Additional investigation is needed to realize reliable control of such synaptic behaviors for practical device implementation. To meet this scientific need, we fabricated MoS2-based memristors and studied their paired-pulse facilitation (PPF) and long-term memory characteristics under different pulse programming settings. This research has provided a guideline for identifying the programming settings for different neuromorphic processes. For example, a specific setting resulting in PPF > 30% and long-term conductance change < 20% has been identified to be suited for processing real-time temporal information. Furthermore, this research also indicates that the MoS2 memristor keeps having an almost constant relative change in conductance but greatly enhanced drive current level under laser illumination. This behavior can enable an easy integration of such memristive devices with state-of-the-art controller circuits for practice neuromorphic control applications. 

Along with the increasing interest in MoS 2 as a promising electronic material, there is also an increasing demand for nanofabrication technologies that are compatible with this material and other relevant layered materials. In addition, the development of scalable nanofabrication approaches capable of directly producing MoS 2 device arrays is an imperative task to speed up the design and commercialize various functional MoS 2 -based devices. The desired fabrication methods need to meet two critical requirements. First, they should minimize the involvement of resist-based lithography and plasma etching processes, which introduce unremovable contaminations to MoS 2 structures. Second, they should be able to produce MoS 2 structures with in-plane or out-of-plane edges in a controlled way, which is key to increase the usability of MoS 2 for various device applications. Here, we introduce an inkjet-defined site-selective (IDSS) method that meets these requirements. IDSS includes two main steps: (i) inkjet printing of microscale liquid droplets that define the designated sites for MoS 2 growth, and (ii) site-selective growth of MoS 2 at droplet-defined sites. Moreover, IDSS is capable of generating MoS 2 with different structures. Specifically, an IDSS process using deionized (DI) water droplets mainly produces in-plane MoS 2 features, whereas the processes using graphene ink droplets mainly produce out-of-plane MoS 2 features rich in exposed edges. Using out-of-plane MoS 2 structures, we have demonstrated the fabrication of miniaturized on-chip lithium ion batteries, which exhibit reversible lithiation/delithiation capacity. This IDSS method could be further expanded as a scalable and reliable nanomanufacturing method for generating miniaturized on-chip energy storage devices.