Gate-Tunable Electrostatic Friction of Grain Boundary in Chemical-Vapor-Deposited MoS₂

Two-dimensional (2D) semiconducting materials, such as MoS2, are widely studied owing to their great potential in advanced electronic devices. However, MoS2 films grown using chemical vapor deposition (CVD) exhibit lower-than-expected properties owing to numerous defects. Among them, grain boundary (GB) is a critical parameter that determines electrical and mechanical properties of MoS2. Herein, we report the gate-tunable electrostatic friction of GBs in CVD-grown MoS2. Using atomic force microscopy (AFM), we found that electrostatic friction of MoS2 is generated by the Coulomb interaction between tip and carriers of MoS2, which is associated with the local band structure of GBs. Therefore, electrostatic friction is enhanced by localized charge carrier distribution at GB, which is linearly related to the loading force of the tip. Our study shows a strong correlation between electrostatic friction and localized band structure in MoS2 GB, providing a novel method for identifying and characterizing GBs of polycrystalline 2D materials

Instantaneous and Repeatable Self-Healing of Fully Metallic Electrodes at Ambient Conditions

Recent approaches in self-healable electrodes use polymers with exhibiting significantly low electrical conductivity, compared to conventional metals. Such self-healable electrodes also require external stimuli to initiate self-healing, or present slow restoration for their intrinsic healing. Herein, we introduce an instantaneous and repeatable self-healing of highly conductive, fully metallic electrodes at ambient conditions. These electrodes consist of silver and liquid metal (with no polymer), and exhibit a sufficiently high conductivity of 2 S/μm. The liquid metal (LM) component enables instantaneous and repeatable self-healing of these electrodes (within a few milliseconds) under no external energy as well as high stretchability. Additionally, the inclusion of silver in this LM improves the mechanical strength of this composite, thereby overcoming the limitation of a pristine LM that has low mechanical strength. Moreover, this composite formation can be effective in preventing the penetration of gallium atoms into different metals, while preserving electrical contact properties. Also the self-healable nature of electrodes enables their outstanding sustainability against electrical breakdown at relatively high electric fields. Furthermore, the compatibility of these self-healable electrodes with conventional photolithography and wet etching facilitates high-resolution patterning for device fabrications, as demonstrated in an example with a self-healable organic light-emitting diode display

Instantaneous and Repeatable Self-Healing of Fully Metallic Electrodes at Ambient Conditions

Recent approaches in self-healable electrodes use polymers with exhibiting significantly low electrical conductivity, compared to conventional metals. Such self-healable electrodes also require external stimuli to initiate self-healing, or present slow restoration for their intrinsic healing. Herein, we introduce an instantaneous and repeatable self-healing of highly conductive, fully metallic electrodes at ambient conditions. These electrodes consist of silver and liquid metal (with no polymer), and exhibit a sufficiently high conductivity of 2 S/μm. The liquid metal (LM) component enables instantaneous and repeatable self-healing of these electrodes (within a few milliseconds) under no external energy as well as high stretchability. Additionally, the inclusion of silver in this LM improves the mechanical strength of this composite, thereby overcoming the limitation of a pristine LM that has low mechanical strength. Moreover, this composite formation can be effective in preventing the penetration of gallium atoms into different metals, while preserving electrical contact properties. Also the self-healable nature of electrodes enables their outstanding sustainability against electrical breakdown at relatively high electric fields. Furthermore, the compatibility of these self-healable electrodes with conventional photolithography and wet etching facilitates high-resolution patterning for device fabrications, as demonstrated in an example with a self-healable organic light-emitting diode display

Instantaneous and Repeatable Self-Healing of Fully Metallic Electrodes at Ambient Conditions

Recent approaches in self-healable electrodes use polymers with exhibiting significantly low electrical conductivity, compared to conventional metals. Such self-healable electrodes also require external stimuli to initiate self-healing, or present slow restoration for their intrinsic healing. Herein, we introduce an instantaneous and repeatable self-healing of highly conductive, fully metallic electrodes at ambient conditions. These electrodes consist of silver and liquid metal (with no polymer), and exhibit a sufficiently high conductivity of 2 S/μm. The liquid metal (LM) component enables instantaneous and repeatable self-healing of these electrodes (within a few milliseconds) under no external energy as well as high stretchability. Additionally, the inclusion of silver in this LM improves the mechanical strength of this composite, thereby overcoming the limitation of a pristine LM that has low mechanical strength. Moreover, this composite formation can be effective in preventing the penetration of gallium atoms into different metals, while preserving electrical contact properties. Also the self-healable nature of electrodes enables their outstanding sustainability against electrical breakdown at relatively high electric fields. Furthermore, the compatibility of these self-healable electrodes with conventional photolithography and wet etching facilitates high-resolution patterning for device fabrications, as demonstrated in an example with a self-healable organic light-emitting diode display

Nanoscale Patterns of Oligonucleotides Formed by Electrohydrodynamic Jet Printing with Applications in Biosensing and Nanomaterials Assembly

The widespread use of DNA in microarrays for applications in biotechnology, combined with its promise in programmed nanomaterials assembly, unusual electronic devices, and other areas has created interest in methods for patterning DNA with high spatial resolution. Techniques based on thermal or piezoelectric inkjet printing are attractive due to their noncontacting nature and their compatibility with diverse materials and substrate types; their modest resolution (i.e., 10−20 μm) represents a major limitation for certain systems. Here we demonstrate the use of an operationally similar printing approach that exploits electrohydrodynamic forces, rather than thermal or acoustic energy, to eject DNA inks through fine nozzles, in a controlled fashion. This DNA printer is capable of resolution approaching 100 nm. A range of experiments on patterns of DNA formed with this printer demonstrates its key features. Example applications in DNA-directed nanoparticle assembly and DNA aptamer-based biosensing illustrate two representative uses of the patterns that can be formed

Nanoscale Patterns of Oligonucleotides Formed by Electrohydrodynamic Jet Printing with Applications in Biosensing and Nanomaterials Assembly

The widespread use of DNA in microarrays for applications in biotechnology, combined with its promise in programmed nanomaterials assembly, unusual electronic devices, and other areas has created interest in methods for patterning DNA with high spatial resolution. Techniques based on thermal or piezoelectric inkjet printing are attractive due to their noncontacting nature and their compatibility with diverse materials and substrate types; their modest resolution (i.e., 10−20 μm) represents a major limitation for certain systems. Here we demonstrate the use of an operationally similar printing approach that exploits electrohydrodynamic forces, rather than thermal or acoustic energy, to eject DNA inks through fine nozzles, in a controlled fashion. This DNA printer is capable of resolution approaching 100 nm. A range of experiments on patterns of DNA formed with this printer demonstrates its key features. Example applications in DNA-directed nanoparticle assembly and DNA aptamer-based biosensing illustrate two representative uses of the patterns that can be formed

Nanoscale Patterns of Oligonucleotides Formed by Electrohydrodynamic Jet Printing with Applications in Biosensing and Nanomaterials Assembly

The widespread use of DNA in microarrays for applications in biotechnology, combined with its promise in programmed nanomaterials assembly, unusual electronic devices, and other areas has created interest in methods for patterning DNA with high spatial resolution. Techniques based on thermal or piezoelectric inkjet printing are attractive due to their noncontacting nature and their compatibility with diverse materials and substrate types; their modest resolution (i.e., 10−20 μm) represents a major limitation for certain systems. Here we demonstrate the use of an operationally similar printing approach that exploits electrohydrodynamic forces, rather than thermal or acoustic energy, to eject DNA inks through fine nozzles, in a controlled fashion. This DNA printer is capable of resolution approaching 100 nm. A range of experiments on patterns of DNA formed with this printer demonstrates its key features. Example applications in DNA-directed nanoparticle assembly and DNA aptamer-based biosensing illustrate two representative uses of the patterns that can be formed

Nanoscale Patterns of Oligonucleotides Formed by Electrohydrodynamic Jet Printing with Applications in Biosensing and Nanomaterials Assembly

The widespread use of DNA in microarrays for applications in biotechnology, combined with its promise in programmed nanomaterials assembly, unusual electronic devices, and other areas has created interest in methods for patterning DNA with high spatial resolution. Techniques based on thermal or piezoelectric inkjet printing are attractive due to their noncontacting nature and their compatibility with diverse materials and substrate types; their modest resolution (i.e., 10−20 μm) represents a major limitation for certain systems. Here we demonstrate the use of an operationally similar printing approach that exploits electrohydrodynamic forces, rather than thermal or acoustic energy, to eject DNA inks through fine nozzles, in a controlled fashion. This DNA printer is capable of resolution approaching 100 nm. A range of experiments on patterns of DNA formed with this printer demonstrates its key features. Example applications in DNA-directed nanoparticle assembly and DNA aptamer-based biosensing illustrate two representative uses of the patterns that can be formed

Magnetic Manipulation of Locomotive Liquid Electrodes for Wireless Active Cardiac Monitoring

For electrocardiogram (ECG) detection, the position of conventional patch-type electrodes based on solid-state metals are difficult to manipulate after attachment and also can lead to poor interface with stretchable, rough skin surfaces. Herein, we present a liquid form of ECG electrodes that can be magnetically reconfigured on human skin by providing its conformal interfacing. These electrodes consist of biocompatible liquid-metal droplets where magnetic particles are homogeneously dispersed, and their conformal contact with skin can yield significantly low impedance as well as high signal-to-noise ratio of ECG peaks. These electrodes are also capable of complex motions such as linear movements, splitting, and merging under external magnetic fields. Furthermore, magnetic manipulation of each electrode position on human skin enables precise monitoring of ECG signals with the change in ECG vectors. The integration of liquid-state electrodes with electronic circuitry demonstrates wireless and continuous ECG monitoring while magnetically moving this entire system on human skin