An introduction to heat transfer

This review comprises a detailed survey of ongoing methodologies for soft actuators, highlighting approaches suitable for nanometer- to centimeter-scale robotic applications. Soft robots present a special design challenge in that their actuation and sensing mechanisms are often highly integrated with the robot body and overall functionality. When less than a centimeter, they belong to an even more special subcategory of robots or devices, in that they often lack on-board power, sensing, computation, and control. Soft, active materials are particularly well suited for this task, with a wide range of stimulants and a number of impressive examples, demonstrating large deformations, high motion complexities, and varied multifunctionality. Recent research includes both the development of new materials and composites, as well as novel implementations leveraging the unique properties of soft materials.

Soft Actuators for Small-Scale Robotics.

Ferroelectrics are essential components in a wide range of applications, including ultrasonic transducers, sensors, and actuators. In the single crystal form, relaxor-PbTiO3 (PT) piezoelectric materials have been extensively studied due to their ultrahigh piezoelectric and electromechanical properties. In this article, a perspective and future development of relaxor-PT crystals are given. Initially, various techniques for the growth of relaxor-PT crystals are reviewed, with crystals up to 100 mm in diameter and 200 mm in length being readily achievable using the Bridgman technique. Second, the characterizations of dielectric and electromechanical properties are surveyed. Boundary conditions, including temperature, electric field, and stress, are discussed in relation to device limitations. Third, the physical origins of the high piezoelectric properties and unique loss characteristics in relaxor-PT crystals are discussed with respect to their crystal structure, phase, engineered domain configuration, macr...

/pdf/high-performance-ferroelectric-relaxor-pbtio3-single-3cp5am04w0.pdf

High performance ferroelectric relaxor-PbTiO3 single crystals: Status and perspective

Advantages and Challenges of Relaxor-PbTiO3 Ferroelectric Crystals for Electroacoustic Transducers- A Review.

Systems including an implantable receiver-stimulator and an implantable controller-transmitter are used for leadless electrical stimulation of body tissues. Cardiac pacing and arrhythmia control is accomplished with one or more implantable receiver-stimulators and an external or implantable controller-transmitter. Systems are implanted by testing external or implantable devices at different tissue sites, observing physiologic and device responses, and selecting sites with preferred performance for implanting the systems. In these systems, a controller-transmitter is activated at a remote tissue location to transmit/deliver acoustic energy through the body to a receiver-stimulator at a target tissue location. The receiver-stimulator converts the acoustic energy to electrical energy for electrical stimulation of the body tissue. The tissue locations(s) can be optimized by moving either or both of the controller-transmitter and the receiver-stimulator to determine the best patient and device responses.

Leadless tissue stimulation systems and methods

This abstract outlines current developments of a micro-assembly facility focusing on studies using a three fingered gripper. Individual fingers of the gripper comprise thin fibers ranging in diameter from 7 to 80 μm that are attached to quartz based oscillators and are capable of sensing proximity, contact, and controlling adhesion forces. To optimize gripper finger performance, an electrolytic etching facility has been used to selectively modify oscillator performance and this system is currently being developed for automated processing. To demonstrate current performance of the gripper system, a micro-CMM contact sensing probe has been assembled and a preliminary performance evaluation is presented.

/pdf/development-of-a-micro-scale-assembly-facility-with-a-three-5divwshoja.pdf

Development of a Micro-scale Assembly Facility with a Three Fingered, Self-aware Assembly Tool and Electro-chemical Etching Capabilities

The authors present a novel closed loop electromagnetic actuator for fine position control. In this, six NdBFe permanent magnets are attached to a linear flexure mechanism. These are, in turn, surrounded by solenoid actuation coils. Feedback is provided by a sensor having sub-nanometre capability. Initial results are presented of a system in which two such springs have been combined to form a tunnelling profilometer. This has been used to profile 35 nm of the surface of a silicon wafer that has been coated with a 20 nm thick gold film. Results indicate nanometre-level resolution and a thermal drift in the probe axis of better than 0.02 nm s-1.

https://iopscience.iop.org/article/10.1088/0957-4484/3/1/007/pdf

A profilometer for surface proximity probe applications

A force characterization device utilizes a flexure having a compliant portion and a solid portion. During operation of a coordinate measuring machine (CMM) on the solid portion of the flexure, a first capacitance probe detects displacement of the solid portion of the flexure in a first dimension and a second capacitance probe detects displacement of the solid portion of the flexure in a second dimension perpendicular to the first dimension. The detected displacements in the first and second dimensions of the solid portion of the flexure are correlated to forces applied to the flexure in the first and second dimensions based on the detected displacements and the predetermined spring constant of the compliant portion of the flexure. A total applied force is determined based on the forces applied to the flexure in the first and second dimensions. The flexure may be utilized for touch-trigger operations or scanning operations of the CMM. For scanning operations, a normal force applied and a coefficient of friction between the contact probe of the CMM and the solid portion of the flexure may be determined from the total applied force and the forces applied in the first and second dimensions.

Dual-axis static and dynamic force characterization device

The application of thin films in low friction bearings is well known but conventional materials (e.g., PTFE or graphite) suffer from poor processability, susceptibility to chemical attack or thermal runaway. In contrast, electrochemically grown conducting polymer films can be readily deposited onto complex surfaces with good thermal properties. The tribological properties of electropolymerized films can also be selected as desired, i.e., a low friction coefficient and a low wear rate; this makes them a promising choice for bearing material in microactuators or other sliding systems.

Electropolymerized films for low friction microactuator bearings

A symmetric ultra-precision spindle design in which all forces of constraint are, within the tolerances of manufacturing and assembly processes, symmetrically arranged about its axis. Additionally this design may require little or no external power other than the forces to rotate the spindle.

Stuart T. Smith

Papers

Development of a Micro-scale Assembly Facility with a Three Fingered, Self-aware Assembly Tool and Electro-chemical Etching Capabilities

A profilometer for surface proximity probe applications

Dual-axis static and dynamic force characterization device

Electropolymerized films for low friction microactuator bearings

Symmetric spindle design