Wen Hwa Chu

Bio: Wen Hwa Chu is an academic researcher from Case Western Reserve University. The author has contributed to research in topics: Deflection (engineering) & Cantilever. The author has an hindex of 1, co-authored 1 publications receiving 248 citations.

Analysis of tip deflection and force of a bimetallic cantilever microactuator

Abstract: The authors present a model of the electromechanical performance of bimetallic cantilever microactuators by deriving the relationship between the tip deflection and change in temperature using a simple analytical approach. The model is verified by comparison with finite element analysis and published experimental data. The maximum tip force generated by a bimetallic cantilever beam is calculated by finding the reaction force needed at the tip to prevent cantilever beam deflection.

Memory effects in complex materials and nanoscale systems

Abstract: Memory effects are ubiquitous in nature and are particularly relevant at the nanoscale where the dynamical properties of electrons and ions strongly depend on the history of the system, at least within certain time scales. We review here the memory properties of various materials and systems which appear most strikingly in their non-trivial, time-dependent resistive, capacitative and inductive characteristics. We describe these characteristics within the framework of memristors, memcapacitors and meminductors, namely memory-circuit elements with properties that depend on the history and state of the system. We examine basic issues related to such systems and critically report on both theoretical and experimental progress in understanding their functionalities. We also discuss possible applications of memory effects in various areas of science and technology ranging from digital to analog electronics, biologically inspired circuits and learning. We finally discuss future research opportunities in the field.

Modeling and optimal design of piezoelectric cantilever microactuators

Abstract: A novel model is described for predicting the static behavior of a piezoelectric cantilever actuator with an arbitrary configuration of elastic and piezoelectric layers. The model is compared to deflection measurements obtained from 500-/spl mu/m-long ZnO cantilever actuators fabricated by surface micromachining. Modeled and experimental results demonstrate the utility of the model for optimizing device design. A discussion of design considerations and optimization of device performance is presented.

High-Performance Multiresponsive Paper Actuators

Abstract: There is an increasing demand for soft actuators because of their importance in soft robotics, artificial muscles, biomimetic devices, and beyond. However, the development of soft actuators capable of low-voltage operation, powerful actuation, and programmable shape-changing is still challenging. In this work, we propose programmable bilayer actuators that operate based on the large hygroscopic contraction of the copy paper and simultaneously large thermal expansion of the polypropylene film upon increasing the temperature. The electrothermally activated bending actuators can function with low voltages (≤ 8 V), low input electric power per area (P ≤ 0.14 W cm–2), and low temperature changes (≤ 35 °C). They exhibit reversible shape-changing behavior with curvature radii up to 1.07 cm–1 and bending angle of 360°, accompanied by powerful actuation. Besides the electrical activation, they can be powered by humidity or light irradiation. We finally demonstrate the use of our paper actuators as a soft gripper r...

Microcantilever Biosensors

Abstract: Microcantilever arrays have been used for multiplexed, label-free detection of biomolecules. Adsorption of analyte molecules on immobilized receptors on the cantilevers result in cantilever bending due to surface free energy variation. Piezoresistive readout of cantilever bending offers a simple method of signal transduction that is compatible with microfabrication. Although the microcantilever-based biosensing appears to high sensitivity and selectivity, reproducibility of the technique appears to be a challenge. We have developed a novel method of immobilizing receptors that increases the reproducibility. We have demonstrated simultaneous detection of cancer and cardiac markers using cantilever arrays with immobilized receptors.

Soft electrothermal actuators using silver nanowire heaters.

Abstract: Low-voltage and extremely flexible electrothermal bimorph actuators were fabricated in a simple, efficient and scalable process. The bimorph actuators were made of flexible silver nanowire (AgNW) based heaters, which exhibited a fast heating rate of 18 °C s−1 and stable heating performance with large bending. The actuators offered the largest bending angle (720°) or curvature (2.6 cm−1) at a very low actuation voltage (0.2 V sq−1 or 4.5 V) among all types of bimorph actuators that have been reported to date. The actuators can be designed and fabricated in different configurations that can achieve complex patterns and shapes upon actuation. Two applications of this type of soft actuators were demonstrated towards biomimetic robotics – a crawling robot that can walk spontaneously on ratchet surfaces and a soft gripper that is capable of manipulating lightweight and delicate objects.