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Abstract Source/Drain extension doping is crucial for minimizing the series resistance of the ungated channel and reducing the contact resistance of field‐effect transistors (FETs) in complementary metal–oxide–semiconductor (CMOS) technology. 2D semiconductors, such as MoS₂and WSe₂, are promising channel materials for beyond‐silicon CMOS. A key challenge is to achieve extension doping for 2D monolayer FETs without damaging the atomically thin material. This work demonstrates extension doping with low‐resistance contacts for monolayer WSe₂p‐FETs. Self‐limiting oxidation transforms a bilayer WSe₂into a hetero‐bilayer of a high‐work‐function WO_xSe_yon a monolayer WSe₂. Then, damage‐free nanolithography defines an undoped nano‐channel, preserving the high on‐current of WO_xSe_y‐doped FETs while significantly improving their on/off ratio. The insertion of an amorphous WO_xSe_yinterlayer under the contacts achieves record‐low contact resistances for monolayer WSe₂over a hole density range of 10¹²to 10¹³cm⁻²(1.2 ± 0.3 kΩ µm at 10¹³cm⁻²). The WO_xSe_y‐doped extension exhibits a sheet resistance as low as 10 ± 1 kΩ □⁻¹. Monolayer WSe₂p‐FETs with sub‐50 nm channel lengths reach a maximum drain current of 154 µA µm⁻¹with an on/off ratio of 10⁷–10⁸. These results define strategies for nanometer‐scale selective‐area doping in 2D FETs and other 2D architectures. 

Abstract The ongoing reduction in transistor sizes drives advancements in information technology. However, as transistors shrink to the nanometer scale, surface and edge states begin to constrain their performance. 2D semiconductors like transition metal dichalcogenides (TMDs) have dangling‐bond‐free surfaces, hence achieving minimal surface states. Nonetheless, edge state disorder still limits the performance of width‐scaled 2D transistors. This work demonstrates a facile edge passivation method to enhance the electrical properties of monolayer WSe₂nanoribbons, by combining scanning transmission electron microscopy, optical spectroscopy, and field‐effect transistor (FET) transport measurements. Monolayer WSe₂nanoribbons are passivated with amorphous WO_xSe_yat the edges, which is achieved using nanolithography and a controlled remote O₂plasma process. The same nanoribbons, with and without edge passivation are sequentially fabricated and measured. The passivated‐edge nanoribbon FETs exhibit 10 ± 6 times higher field‐effect mobility than the open‐edge nanoribbon FETs, which are characterized with dangling bonds at the edges. WO_xSe_yedge passivation minimizes edge disorder and enhances the material quality of WSe₂nanoribbons. Owing to its simplicity and effectiveness, oxidation‐based edge passivation could become a turnkey manufacturing solution for TMD nanoribbons in beyond‐silicon electronics and optoelectronics. 

A long-unrealized goal in solid-state nanopore sensing is to achieve out-of-plane electrical sensing and control of DNA during translocation, which is a prerequisite for base-by-base ratcheting that enables DNA sequencing in biological nanopores. Two-dimensional (2D) heterostructures, with their capability to construct out-of-plane electronics with atomic layer precision, are ideal yet unexplored candidates for use as electrical sensing membranes. Here, we demonstrate a nanopore architecture using a vertical 2D heterojunction diode consisting of p-type WSe₂on n-type MoS₂. This diode exhibits rectified interlayer tunneling currents modulated by ionic potential, while the heterojunction potential reciprocally rectifies ionic transport through the nanopore. We achieve concurrent detection of DNA translocation using both ionic and diode currents and demonstrate a 2.3-fold electrostatic slowing of average translocation speed. Encapsulation layers enhance chemical and mechanical stability and durability while preserving the spatial resolution of atomically sharp 2D heterointerface for sensing. These results establish a paradigm for out-of-plane electrical sensing of single biomolecules. 

Neuronal control of skeletal muscle function is ubiquitous across species for locomotion and doing work. In particular, emergent behaviors of neurons in biohybrid neuromuscular systems can advance bioinspired locomotion research. Although recent studies have demonstrated that chemical or optogenetic stimulation of neurons can control muscular actuation through the neuromuscular junction (NMJ), the correlation between neuronal activities and resulting modulation in the muscle responses is less understood, hindering the engineering of high-level functional biohybrid systems. Here, we developed NMJ-based biohybrid crawling robots with optogenetic mouse motor neurons, skeletal muscles, 3D-printed hydrogel scaffolds, and integrated onboard wireless micro–light-emitting diode (μLED)–based optoelectronics. We investigated the coupling of the light stimulation and neuromuscular actuation through power spectral density (PSD) analysis. We verified the modulation of the mechanical functionality of the robot depending on the frequency of the optical stimulation to the neural tissue. We demonstrated continued muscle contraction up to 20 minutes after a 1-minute-long pulsed 2-hertz optical stimulation of the neural tissue. Furthermore, the robots were shown to maintain their mechanical functionality for more than 2 weeks. This study provides insights into reliable neuronal control with optoelectronics, supporting advancements in neuronal modulation, biohybrid intelligence, and automation. 

Biohybrid robots, composed of cellular actuators and synthetic scaffolds, have garnered much attention in recent years owing to the advantages provided by their biological components. In recent years, various forms of biohybrid robots have been developed that are capable of life-like movements, such as walking, swimming, and gripping. Specifically, for walking or crawling biorobots, there is a need for complex functionality and versatile and robust fabrication processes. Here, we designed and fabricated multi-actuator biohybrid walkers with multi-directional walking capabilities in response to noninvasive optical stimulation through a scalable modular biofabrication process. Our new fabrication approach provides a constant mechanical strain throughout the cellular differentiation and maturation process. This maximizes the myotube formation and alignment, limits passive bending, and produces higher active forces. These demonstrations of the new fabrication process and bioactuator designs can pave the way for advanced multi-cellular biohybrid robots and enhance our understanding of the emergent behaviors of these multi-cellular engineered living systems. 

A silicon integrated microfluidics system prints picoliter-segmented analytes for attomole-level chemical analysis with mass spectrometry imaging. 

Myokines and exosomes, originating from skeletal muscle, are shown to play a significant role in maintaining brain homeostasis. While exercise has been reported to promote muscle secretion, little is known about the effects of neuronal innervation and activity on the yield and molecular composition of biologically active molecules from muscle. As neuromuscular diseases and disabilities associated with denervation impact muscle metabolism, we hypothesize that neuronal innervation and firing may play a pivotal role in regulating secretion activities of skeletal muscles. We examined this hypothesis using an engineered neuromuscular tissue model consisting of skeletal muscles innervated by motor neurons. The innervated muscles displayed elevated expression of mRNAs encoding neurotrophic myokines, such as interleukin-6, brain-derived neurotrophic factor, and FDNC5, as well as the mRNA of peroxisome-proliferator-activated receptor γ coactivator 1α, a key regulator of muscle metabolism. Upon glutamate stimulation, the innervated muscles secreted higher levels of irisin and exosomes containing more diverse neurotrophic microRNAs than neuron-free muscles. Consequently, biological factors secreted by innervated muscles enhanced branching, axonal transport, and, ultimately, spontaneous network activities of primary hippocampal neurons in vitro. Overall, these results reveal the importance of neuronal innervation in modulating muscle-derived factors that promote neuronal function and suggest that the engineered neuromuscular tissue model holds significant promise as a platform for producing neurotrophic molecules.