3D-Printing and Machine Learning Control of Soft Ionic Polymer-Metal Composite Actuators.

This paper presents a new manufacturing and control paradigm for developing soft ionic polymer-metal composite (IPMC) actuators for soft robotics applications. First, an additive manufacturing method that exploits the fused-filament (3D printing) process is described to overcome challenges with existing methods of creating custom-shaped IPMC actuators. By working with ionomeric precursor material, the 3D-printing process enables the creation of 3D monolithic IPMC devices where ultimately integrated sensors and actuators can be achieved.

Nanothorn electrodes for ionic polymer-metal composite artificial muscles.

Ionic polymer-metal composites (IPMCs) have recently received tremendous interest as soft biomimetic actuators and sensors in various bioengineering and human affinity applications, such as artificial muscles and actuators, aquatic propulsors, robotic end-effectors, and active catheters. Main challenges in developing biomimetic actuators are the attainment of high strain and actuation force at low operating voltage. Here we first report a nanostructured electrode surface design for IPMC comprising platinum nanothorn assemblies with multiple sharp tips.

Range-based control of dual-stage nanopositioning systems.

A novel dual-stage nanopositioner control framework is presented that considers range constraints. Dual-stage nanopositioners are becoming increasingly popular in applications such as scanning probe microscopy due to their unique ability to achieve long-range and high-speed operation. The proposed control approach addresses the issue that some precision positioning trajectories are not achievable through existing control schemes.

Invited review article: high-speed flexure-guided nanopositioning: mechanical design and control issues.

Recent interest in high-speed scanning probe microscopy for high-throughput applications including video-rate atomic force microscopy and probe-based nanofabrication has sparked attention on the development of high-bandwidth flexure-guided nanopositioning systems (nanopositioners). Such nanopositioners are designed to move samples with sub-nanometer resolution with positioning bandwidth in the kilohertz range. State-of-the-art designs incorporate uniquely designed flexure mechanisms driven by compact and stiff piezoelectric actuators.

Compact ultra-fast vertical nanopositioner for improving scanning probe microscope scan speed.

The mechanical design of a high-bandwidth, short-range vertical positioning stage is described for integration with a commercial scanning probe microscope (SPM) for dual-stage actuation to significantly improve scanning performance. The vertical motion of the sample platform is driven by a stiff and compact piezo-stack actuator and guided by a novel circular flexure to minimize undesirable mechanical resonances that can limit the performance of the vertical feedback control loop. Finite element analysis is performed to study the key issues that affect performance.

Cyclic energy harvesting from pyroelectric materials.

A method of continuously harvesting energy from pyroelectric materials is demonstrated using an innovative cyclic heating scheme. In traditional pyroelectric energy harvesting methods, static heating sources are used, and most of the available energy has to be harvested at once. A cyclic heating system is developed such that the temperature varies between hot and cold regions.

Bridging the gap between conventional and video-speed scanning probe microscopes.

A major disadvantage of scanning probe microscopy is the slow speed of image acquisition, typically less than one image per minute. This paper describes three techniques that can be used to increase the speed of a conventional scanning probe microscope by greater than one hundred times. This is achieved by the combination of high-speed vertical positioning, sinusoidal scanning, and high-speed image acquisition.

Charge drives for scanning probe microscope positioning stages.

Due to hysteresis exhibited by piezoelectric actuators, positioning stages in scanning probe microscopes require sensor-based closed-loop control. Although closed-loop control is effective at eliminating non-linearity at low scan speeds, the bandwidth compared to open loop is severely reduced. In addition, sensor noise significantly degrades achievable resolution in closed loop.

Control Issues in High-speed AFM for Biological Applications: Collagen Imaging Example.

This article considers the precision positioning problem associated with high-speed operation of the Atomic Force Microscope (AFM), and presents an inversion-based control approach to achieve precision positioning. Although AFMs have high (nanoscale) spatial resolution, a problem with current AFM systems is that they have low temporal resolution, i.e.