California Institute of Technology

Louisiana State University and Agricultural & Mechanical College

Kaushik Bhattacharya

Guruswami Ravichandran

Beverley McKeon

Md Zubaer Hossain

Chun-Jen Hsueh

Axel Scherer

Harry A Atwater

Demetri Psaltis

Michael Ortiz

Yi-Chung Shu

Blaise Aurélien Bourdin

Rongjing Zhang

Guruwaminaidu Ravichandran

Doron Shilo

Kaushik Dayal

Paul Mazur

Matthew Dicken

Eric Burcsu

A multilayered active surface is presented whose rugosity can be controlled by an applied electrical field. Varying the applied electrical field can control the rugosity of the surface which makes contact with a fluid, and thereby can affect instabilities of the boundary layer. A middle layer of the multilayered active surface can be made of a compliant electroactive material. In some cases, a pre-stretch in the middle layer can predefine a rugosity of the multilayered active surface without an applied electrical field, in which case an applied electrical field can further alter the rugosity in both amplitude and spatial periodicity and ultimately result to a smooth surface for a higher value of the applied electrical field. A top layer and a bottom layer are constructed using conductive material and uses as electrodes coupled to a voltage source to generate the electric field that controls the rugosity of the surface.

Flow control technique by dielectric materials

Systems and methods in accordance with embodiments of the invention determine the effective toughness of a given material, and also implement materials possessing improved effective toughness values. In one embodiment, a method of determining the effective toughness of a material includes: causing a crack to propagate through the material; where the relative constant velocity and the relative overall direction are prescribed and maintained for the duration of the propagation of the crack through the material; measuring the energy release rate of the crack as it propagates through the material; and defining the effective toughness of the material as the maximum value of the measured energy release rate.

Systems and methods for determining the effective toughness of a material and for implementing materials possessing improved effective toughness characteristics

Methods for measuring the effective fracture toughness in a material are described. A rail and roller system are used to apply a gradual force to a specimen. The time-dependent force creates a steady fracture development that allows a camera to record the progressive fracture in the material. Mathematical methods can then be used to analyze the fracture progression and determine the effective fracture toughness.

Measurement of fracture toughness of heterogeneous materials

A structure configured to modify its surface morphology between a smooth state and a rough state in response to an applied stress. In demonstrated examples, a soft (PDMS) substrate is produced, and is pre-strained. A relatively stiff overlayer of a metal, such as chromium and gold, is applied to the substrate. When the pre-strained substrate is allowed to relax, the free surface of the stiff overlayer is forced to become distorted, yielding a free surface having a roughness of less than 1 millimeter. Repeated application and removal of the applied stress has been shown to yield reproducible changes in the morphology of the free surface. An application of such morphing free surface is to control a boundary layer transition of an aerodynamic fluid flowing over the surface.

Morphing surfaces for the control of boundary layer transition

The present invention relates to the field measuring the mechanical response of micro-electro-mechanical systems. More specifically, the present invention pertains to a method and apparatus that allows the direct control of the load applied to a Micro-Electro-Mechanical System in order to measure the mechanical response. The system comprises a loading sub-system, a displacement measurement sub-system, and an optional observation sub-system.

Method and apparatus for measuring the mechanical response of micro-electro-mechanical systems

Systems and methods for manipulating light with tunable ferroelectric photonic devices. Devices having tunable properties that exhibit photonic bandgap behavior are fabricated from ferroelectric materials. Apparatus is provided to apply tuning signals to the ferroelectric material using one or more of electric fields, mechanical forces, optical fields, and thermal fields. Control circuitry is provided to generate the control signals needed to apply the tuning signals. Input and output ports are provided to allow input signals to be received and to provide output signals. In some cases, a feedback loop is provided to use a portion of the output signal as a diagnostic signal for control of the operation of the device within an acceptable range. It is expected that ferroelectric photonic devices operating according to principles of the invention will be useful for a wide variety of applications, including optical switching, optical modulation, optical computing, and performing logic optically.

Ferroelectric nanophotonic materials and devices

An electrostrictive actuator incorporating a single crystal ferroelectric material is subjected to combined electrical and mechanical loading. Electrodes are used to generate an electric field in a ferroelectric plate. The subsequent domain switching process produces large strains that can be recovered by applying stress with a mechanical load.

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Pasadena, CA, United States of America

Kaushik Bhattacharya