The field of molecular electronics, also known as moletronics, deals with the assembly of molecular electronic components using molecules as the building blocks. It is an interdisciplinary field that includes physics, chemistry, materials science, and engineering. Moletronics mainly deals with the reduction of size of silicon components. Novel research has been performed in developing electrical-equivalent molecular components. Moletronics has established its influence in electronic and photonic applications, such as conducting polymers, photochromics, organic superconductors, electrochromics, and many more. Since there is a need to reduce the size of the silicon chip, attaining such technology at the molecular level is essential. Although the experimental verification and modeling of molecular devices present a daunting task, vital breakthroughs have been achieved in this field. This article combines an overview of various molecular components, such as molecular transistors, diodes, capacitors, wires, and insulators, with a discussion of the potential applications of different molecules suitable for such components. We emphasize future developments and provide a brief review of different achievements that have been made regarding graphene-based molecular devices.
Absolute distance measurement is a fundamental technique in mobile and large-scale dimensional metrology. Dual-comb ranging is emerging as a powerful tool that exploits phase resolution and frequency accuracy for high-precision and fast-rate distance measurement. Using two coherent frequency combs, dual-comb ranging allows time and phase response to be measured rapidly. It breaks through the limitations related to the responsive bandwidth, ambiguity range, and dynamic measurement characteristics of conventional ranging tools. This review introduces dual-comb ranging and summarizes the key techniques for realizing this ranging tool. As optical frequency comb technology progresses, dual-comb ranging shows promise for various professional applications.
Ultra-short laser pulses possess many advantages for materials processing. Ultrafast laser has a significantly low thermal effect on the areas surrounding the focal point; therefore, it is a promising tool for micro- and submicro-sized precision processing. In addition, the nonlinear multiphoton absorption phenomenon of focused ultra-short pulses provides a promising method for the fabrication of various structures on transparent material, such as glass and transparent polymers. A laser direct writing process was applied in the fabrication of high-performance three-dimensional (3D) structured multilayer micro-supercapacitors (MSCs) on polymer substrates exhibiting a peak specific capacitance of 42.6 mF·cm−2 at a current density of 0.1 mA·cm−2. Furthermore, a flexible smart sensor array on a polymer substrate was fabricated for multi-flavor detection. Different surface treatments such as gold plating, reduced-graphene oxide (rGO) coating, and polyaniline (PANI) coating were accomplished for different measurement units. By applying principal component analysis (PCA), this sensing system showed a promising result for flavor detection. In addition, two-dimensional (2D) periodic metal nanostructures inside 3D glass microfluidic channels were developed by all-femtosecond-laser processing for real-time surface-enhanced Raman spectroscopy (SERS). The processing mechanisms included laser ablation, laser reduction, and laser-induced surface nano-engineering. These works demonstrate the attractive potential of ultra-short pulsed laser for surface precision manufacturing.
This paper presents an atomic force microscopy (AFM) tip-based nanomachining method to fabricate periodic nanostructures. This method relies on combining the topography generated by machined grooves with the topography resulting from accumulated pile-up material on the side of these grooves. It is shown that controlling the distance between adjacent and parallel grooves is the key factor in ensuring the quality of the resulting nanostructures. The presented experimental data show that periodic patterns with good quality can be achieved when the feed value between adjacent scratching paths is equal to the width between the two peaks of material pile-up on the sides of a single groove. The quality of the periodicity of the obtained nanostructures is evaluated by applying one- and two-dimensional fast Fourier transform (FFT) algorithms. The ratio of the area of the peak part to the total area in the normalized amplitude–frequency characteristic diagram of the cross-section of the measured AFM image is employed to quantitatively analyze the periodic nanostructures. Finally, the optical effect induced by the use of machined periodic nanostructures for surface colorization is investigated for potential applications in the fields of anti-counterfeiting and metal sensing.
This paper presents a dual-platform scanner for dental reconstruction based on a three-dimensional (3D) laser-scanning method. The scanner combines translation and rotation platforms to perform a holistic scanning. A hybrid calibration method for laser scanning is proposed to improve convenience and precision. This method includes an integrative method for data collection and a hybrid algorithm for data processing. The integrative method conveniently collects a substantial number of calibrating points with a stepped gauge and a pattern for both the translation and rotation scans. The hybrid algorithm, which consists of a basic model and a compensation network, achieves strong stability with a small degree of errors. The experiments verified the hybrid calibration method and the scanner application for the measurement of dental pieces. Two typical dental pieces were measured, and the experimental results demonstrated the validity of the measurement that was performed using the dual-platform scanner. This method is effective for the 3D reconstruction of dental pieces, as well as that of objects with irregular shapes in engineering fields.
In this investigation, a picosecond laser was employed to fabricate surface textures on a Stavax steel substrate, which is a key material for mold fabrication in the manufacturing of various polymer products. Three main types of surface textures were fabricated on a Stavax steel substrate: periodic ripples, a two-scale hierarchical two-dimensional array of micro-bumps, and a micro-pits array with nano-ripples. The wettability of the laser-textured Stavax steel surface was converted from its original hydrophilicity into hydrophobicity and even super-hydrophobicity after exposure to air. The results clearly show that this super-hydrophobicity is mainly due to the surface textures. The ultrafast laser-induced catalytic effect may play a secondary role in modifying the surface chemistry so as to lower the surface energy. The laser-induced surface textures on the metal mold substrates were then replicated onto polypropylene substrates via the polymer injection molding process. The surface wettability of the molded polypropylene was found to be changed from the original hydrophilicity to super-hydrophobicity. This developed process holds the potential to improve the performance of fabricated plastic products in terms of wettability control and easy cleaning.
Metallic biomaterials are increasingly being used in various medical applications due to their high strength, fracture resistance, good electrical conductivity, and biocompatibility. However, their practical applications have been largely limited due to poor surface performance. Laser microprocessing is an advanced method of enhancing the surface-related properties of biomaterials. This work demonstrates the capability of laser microprocessing for biomedical metallic materials including magnesium and titanium alloys, with potential applications in cell adhesion and liquid biopsy. We investigate laser-material interaction, microstructural evolution, and surface performance, and analyze cell behavior and the surface-enhanced Raman scattering (SERS) effect. Furthermore, we explore a theoretical study on the laser microprocessing of metallic alloys that shows interesting results with potential applications. The results show that cells exhibit good adhesion behavior at the surface of the laser-treated surface, with a preferential direction based on the textured structure. A significant SERS enhancement of 6 × 103 can be obtained at the laser-textured surface during Raman measurement.
Rechargeable lithium-ion batteries (LIBs) afford a profound impact on our modern daily life. However, LIBs are approaching the theoretical energy density, due to the inherent limitations of intercalation chemistry; thus, they cannot further satisfy the increasing demands of portable electronics, electric vehicles, and grids. Therefore, battery chemistries beyond LIBs are being widely investigated. Next-generation lithium (Li) batteries, which employ Li metal as the anode and intercalation or conversion materials as the cathode, receive the most intensive interest due to their high energy density and excellent potential for commercialization. Moreover, significant progress has been achieved in Li batteries attributed to the increasing fundamental understanding of the materials and reactions, as well as to technological improvement. This review starts by summarizing the electrolytes for next-generation Li batteries. Key challenges and recent progress in lithium-ion, lithium–sulfur, and lithium–oxygen batteries are then reviewed from the perspective of energy and chemical engineering science. Finally, possible directions for further development in Li batteries are presented. Next-generation Li batteries are expected to promote the sustainable development of human civilization.
Fault tolerance is essential for the maneuverability of self-propelled biomimetic robotic fish in real-world aquatic applications. This paper explores the fault-tolerance control problem of a free-swimming robotic fish with multiple moving joints and a stuck tail joint. The created control system is composed of two main components: a feedback controller and a feedforward compensator. Specifically, the bio-inspired central pattern generator-based feedback controller is designed to make the robotic fish robust to external disturbances, while the feedforward compensator speeds up the convergence of the overall control system. Simulations are performed for control system analysis and performance validation of the faulty robotic fish. The experimental results demonstrate that the proposed fault-tolerant control method is able to effectively regulate the faulty robotic fish, allowing it to complete the desired motion in the presence of damage and thereby improving both the stability and the lifetime of the real robotic system.
A wearable force-feedback glove is a promising way to enhance the immersive sensation when a user interacts with virtual objects in virtual reality scenarios. Design challenges for such a glove include allowing a large fingertip workspace, providing a desired force sensation when simulating both free- and constrained-space interactions, and ensuring a lightweight structure. In this paper, we present a force-feedback glove using a pneumatically actuated mechanism mounted on the dorsal side of the user’s hand. By means of a triple kinematic paired link with a curved sliding slot, a hybrid cam-linkage mechanism is proposed to transmit the resistance from the pneumatic piston rod to the fingertip. In order to obtain a large normal component of the feedback force on the user’s fingertip, the profile of the sliding slot was synthesized through an analysis of the force equilibrium on the triple kinematic paired link. A prototype five-fingered glove with a mass of 245 g was developed, and a wearable force-measurement system was constructed to permit the quantitative evaluation of the interaction performance in both free and constrained space. The experimental results confirm that the glove can achieve an average resistance of less than 0.1 N in free-space simulation and a maximum fingertip force of 4 N in constrained-space simulation. The experiment further confirms that this glove permits the finger to move freely to simulate typical grasping gestures.
Measuring the absolute protein expression quantity for a specific promoter is necessary in the fields of both molecular biology and synthetic biology. The strength of a promoter is traditionally characterized by measuring the fluorescent intensity of the fluorescent protein downstream of the promoter. Until now, measurement of the absolute protein expression quantity for a promoter, however, has been unsuccessful in synthetic biology. The fact that the protein coding sequence influences the expression level for different proteins, and the inconvenience of measuring the absolute protein expression level, present a challenge to absolute quantitative measurement. Here, we introduce a new method that combines the insulator RiboJ with the standard fluorescence curve in order to measure the absolute protein expression quantity quickly; this method has been validated by modeling verification. Using this method, we successfully measured nine constitutive promoters in the Anderson promoter family. Our method provides data with higher accuracy for pathway design and is a straightforward way to standardize the strength of different promoters.
Poly(ethylene terephthalate) hydrolase (PETase) from Ideonella sakaiensis exhibits a strong ability to degrade poly(ethylene terephthalate) (PET) at room temperature, and is thus regarded as a potential tool to solve the issue of polyester plastic pollution. Therefore, we explored the interaction between PETase and the substrate (a dimer of the PET monomer ethylene terephthalate, 2PET), using a model of PETase and its substrate. In this study, we focused on six key residues around the substrate-binding groove in order to create novel high-efficiency PETase mutants through protein engineering. These PETase mutants were designed and tested. The enzymatic activities of the R61A, L88F, and I179F mutants, which were obtained with a rapid cell-free screening system, exhibited 1.4 fold, 2.1 fold, and 2.5 fold increases, respectively, in comparison with wild-type PETase. The I179F mutant showed the highest activity, with the degradation rate of a PET film reaching 22.5 mg per μmol·L−1 PETase per day. Thus, this study has created enhanced artificial PETase enzymes through the rational protein engineering of key hydrophobic sites, and has further illustrated the potential of biodegradable plastics.