Liquid infiltration is an efficient way to densify carbon nanotubes (CNTs) and was used to strengthen CNT fibres in the method of array spinning. Rather than the volatility, the dipole moment of solvent plays a more important role in determining the densification level. The fibres densified by highly polar but non-volatile solvents such as N , N -dimethylformamide, dimethyl sulphoxide, and N -methyl-2-pyrrolidone were 100–200 MPa stronger than those by ethanol and acetone. Ethylene glycol is the most efficient solvent due to its two polar OH groups and improved the fibre strength to 1.45 GPa. Long chain or cross-linked polymers like polyvinyl alcohol, polyimide, and bismaleimide (BMI) were introduced into CNT fibres by infiltration with aid of polar solvents. These polymers reinforced the fibres significantly, as they can connect non-neighboring CNTs and benefit the load transfer. The strongest CNT/BMI fibre was 2.38 GPa in strength and 110 GPa in modulus.

Enhancement of carbon nanotube ﬁbres using diﬀerent solvents and polymers

Soft materials possess several distinctive characteristics, such as controllable deformation, infinite degrees of freedom, and self-assembly, which make them promising candidates for building soft machines, robots, and haptic interfaces. In this Review, we give an overview of recent advances in these areas, with an emphasis on two specific topics: bio-inspired design and additive manufacturing. Biology is an abundant source of inspiration for functional materials and systems that mimic the function or mechanism of biological tissues, agents, and behaviors. Additive manufacturing has enabled the fabrication of materials and structures prevalent in biology, thereby leading to more-capable soft robots and machines. We believe that bio-inspired design and additive manufacturing have been, and will continue to be, important tools for the design of soft robots.

Bio-inspired Design and Additive Manufacturing of Soft Materials, Machines, Robots, and Haptic Interfaces

The microvalve is one of the most important components in microfluidics. With decades of development, the microvalve has been widely used in many industries such as life science, chemical engineering, chip, and so forth. This paper presents a comprehensive review of the progress made over the past years about microvalves based on different actuation mechanisms. According to driving sources, plenty of actuation mechanisms are developed and adopted in microvalves, including electricity, magnetism, gas, material and creature, surface acoustic wave, and so on. Although there are currently a variety of microvalves, problems such as leakage, low precision, poor reliability, high energy consumption, and high cost still exist. Problems deserving to be further addressed are suggested, aimed at materials, fabrication methods, controlling performances, flow characteristics, and applications.

/pdf/actuation-mechanism-of-microvalves-a-review-g5ryvu4dso.pdf

Actuation Mechanism of Microvalves: A Review.

This work aims to build inclusive vision of the Internet of Things (IoT), Internet of Everything (IoE), Tactile Internet and 5G, leveraging on MEMS technology, with focus on Energy Harvesters (EH-MEMS) and Radio Frequency passives (RF-MEMS). The IoT is described, stressing the pervasivity of sensing/actuating functions. High-level performances 5G will have to score are reported. Unifying vision of the mentioned paradigms is then built. The IoT evolves into the IoE by overtaking the concept of thing. Further step to Tactile Internet requires significant reduction in latency, it being enabled by 5G. The discussion then moves closer to the hardware components level. Sets of specifications driven by IoT and 5G applications are derived. Concerning the former, the attention is concentrated on typical power requirements imposed by remote wireless sensing nodes. Regarding the latter, a set of reference specifications RF passives will have to meet in order to enable 5G is developed. Once quantitative targets are set, a brief state of the art of EH-MEMS and RF-MEMS solutions is developed, targeting the IoT and 5G, respectively. In both scenarios, it will be demonstrated that MEMS are able to address the requirements previously listed, concerning EH from various sources and RF passive components. In conclusion, the frame of reference depicted in this work outlines a relevant potential borne by EH-MEMS and RF-MEMS solutions within the unified scenario of IoT, IoE, Tactile Internet and 5G, making the forecast of future relentless growth of MEMS-based devices, more plausible and likely to take place.

Internet of things (IoT); internet of everything (IoE); tactile internet; 5G – A (not so evanescent) unifying vision empowered by EH-MEMS (energy harvesting MEMS) and RF-MEMS (radio frequency MEMS)

The design, fabrication, and characterization of a new type of tactile display for people with blindness or low vision is reported Each tactile element comprises a piezoelectric extensional actuator that vibrates in plane, with a microfabricated scissor mechanism to convert the in-plane actuations into robust, higher-amplitude, out-of-plane (vertical) vibrations that are sensed with the finger pads When the tactile elements are formed into a 2D array, information can be conveyed to the user by varying the pattern of vibrations in space and time Analytical models and finite element analysis were used to design individual tactile elements, which were implemented with PZT actuators and both SU-8 and 3D-printed scissor amplifiers The measured displacements of these 3 mm × 10 mm, MEMS-enabled tactile elements exceed 10 µm, in agreement with models, with measured forces exceeding 45 mN The performance of the MEMS-enabled tactile elements is compared with the performance of larger, fully-macroscale tactile elements to demonstrate the scale dependence of the devices The creation of a 28-element prototype is also reported, and the qualitative user experience with the individual tactile elements and displays is described

http://iopscience.iop.org/article/10.1088/0960-1317/24/12/125014/pdf

Scalable, MEMS-enabled, vibrational tactile actuators for high resolution tactile displays

The design, fabrication, and test of a new type of tactile display for the blind is reported. An array of piezoelectric extensional actuators vibrates in plane, and microfabricated scissor mechanisms convert the in-plane actuations into robust, higher-amplitude, out-of-plane vibrations. Information can be conveyed by varying the vibration patterns in space and time. Analytical and FEM models were used to design individual tactile elements, which were implemented with PZT actuators and both SU-8 and 3D-printed scissor amplifiers. The measured displacements of 3 mm x 10 mm tactile elements exceed 10 μm, in agreement with models, with measured forces exceeding 45 mN. The creation of a 28-element prototype is also reported.

/pdf/compact-scalable-high-resolution-mems-enabled-tactile-f7w1teeld4.pdf

Compact, scalable, high-resolution, mems-enabled tactile displays

The design, fabrication, and characterization of an out-of-plane micro tactile actuator that employs pivot hinges fabricated by a multilayer self-aligned approach to deliver exceptional high force and large displacement are demonstrated. The device includes a piezoelectric extensional actuator that vibrates in plane and a micro-fabricated motion amplifier to convert the in-plane vibrations to larger out-of-plane vibrations. These advances are enabled by a self-aligned assembly process that eliminates the need to fabricate re-entrant SU-8 multilayers. For pivot-hinged actuators with 10 mm2 and 2 mm2 areas, maximum displacements of 9.8 μm and 5.5 μm respectively and maximum forces of 9.6 mN and 5.9 mN respectively are reported.

A pivot-hinged, multilayer SU-8 micro motion amplifier assembled by a self-aligned approach

A passively self-aligned, assembly-based process for rapidly creating compact, micro-barrel hinges with unconstrained rotation from SU-8 epoxy is presented. The alignment process takes places in two stages: a coarse alignment stage guided by external dowel pins followed by a fine alignment stage driven by the hinges' features themselves. The assembly of pins into housings circumvents the design rules for minimum gap between features of given thickness in SU-8 processing, enabling reduced hinge clearance for minimization of “side play”. The present hinges' fabrication and function are demonstrated through the design, implementation, and characterization of a displacement-amplifying, out-of-plane, scissor-based actuator that is driven by an in-plane, piezoelectric extensional actuator. The micro-barrel hinge enabled motion amplifier comprises six functional SU-8 multilayer plates joined by three layers of adhesives. Each functional plate comprises two or three layers of SU-8 fabricated by multiple exposures and a single development step. Displacements of up to 11.5 μm and forces of up to 10.5 mN are measured for the 10 mm2 actuator, corresponding to a displacement and force per unit area of up to 1.15 μm/mm2 and 1.05 mN/mm2 respectively and offering potential solutions for applications like haptic interfaces and micropumps.

Passively self-aligned assembly of compact barrel hinges for high-performance, out-of-plane mems actuators

The design, fabrication, and demonstration of a set of 2 mm2, high-force actuators that combine piezoelectric in-plane actuators with MEMS-enabled scissor mechanisms (motion amplifiers) to simultaneously produce high out-of-plane forces and large out-of-plane displacements are presented. The microscissor motion amplifier employs two layers of lithographically-patterned SU-8 microstructure laminated with a thin film of structural polyimide and adhesive to form hinges. Performance is optimized by varying layer thickness and adhesive types. Measured displacements of >3 μm and measured forces of >5 mN are observed, corresponding to a displacement per unit area of 1.6 μm/mm2 and a force per unit area of 2.6 mN/mm2. Cyanoacrylate adhesive provides superior performance to silicone adhesive, with larger force output. Thicker polyimide hinges provide smaller displacement but greater force than thinner polyimide hinges. These powerful, compact actuators have significant potential for high-force applications like tactile displays and micropumps.

https://iopscience.iop.org/article/10.1088/1742-6596/660/1/012026/pdf

Xin Xie

Papers

Scalable, MEMS-enabled, vibrational tactile actuators for high resolution tactile displays

Compact, scalable, high-resolution, mems-enabled tactile displays

A pivot-hinged, multilayer SU-8 micro motion amplifier assembled by a self-aligned approach

Passively self-aligned assembly of compact barrel hinges for high-performance, out-of-plane mems actuators

A high-force, out-of-plane actuator with a MEMS-enabled microscissor motion amplifier