Giulia Lanzara

A Spider-Web-Like Highly Expandable Sensor Network for Multifunctional Materials

www.MaterialsViews.com C O M M A Spider-Web-Like Highly Expandable Sensor Network for Multifunctional Materials U N IC A By Giulia Lanzara , * Nathan Salowitz , Zhiqiang Guo , and Fu-Kuo Chang IO N The skin of living animals is an inspiration for the next generation of materials, devices, and structures. Human skin is sensitive to pressure, strain, and temperature; [ 1 , 2 ] dolphins or bats drastically reduce drag by sensing fl uid fl ow [ 3–5 ] and adapting either their skin shape [ 6 , 7 ] or rigidity; [ 8 ] and snakes use their skin to detect vibrations. [ 9 ] The fundamental common factor in these examples is that the living tissue is integrated with a network of distributed nanoor microscale sensors and actuators. To mimic such systems, novel materials and devices, such as paperlike displays, [ 10–12 ]

Bio-inspired stretchable network-based intelligent composites

The human skin hosts an array of sensors that are capable of detecting and interpreting many traits important to how we function and survive. The goal of mimicking this capability in composites to create intelligent composite materials has led to the development of a bio-inspired stretchable network composed of numerous micro-fabricated sensors capable of detecting multiple stimuli. The components of the network are small scale and flexible making the network embeddable within complexly shaped composite layups and flexible structures with minimal impact on the host structure. This paper outlines recent progress in ongoing work to develop the bio-inspired network in order to create intelligent composite materials.

An Approach to Cost-Effective, Robust, Large-Area Electronics using Monolithic Silicon

We have developed an approach to build large-area electronics from monolithic silicon integrated circuits. The method used deep reactive ion etching to structure a monolithic silicon substrate into a stretchable, two-dimensional, wired network that can be expanded to cover large planar or curved surfaces to realize high-performance, large-area, monolithic silicon electronics in a cost-effective manner. This approach has applications in sensing, smart materials, electronic textile,RFID tag and microconcentrator solar cell manufacturing.

Micro-fabricated, expandable temperature sensor network for macro-scale deployment in composite structures

We have developed methods for creating a highly expandable temperature sensor network for distributed temperature measurement. Stresses and strains due to network expansion are minimized through finite element analysis. Through the use of a uniquely patterned polyimide substrate and wire pattern an expansion ratio of 1,000% is achieved and the electrical resistance of components is maintained from pre-expansion to full expansion. Platinum resistance temperature detectors and electrodes are integrated directly in the polyimide-based network through a non-standard micro fabrication process. Calibration and interpolation algorithms have been developed for temperature measurement. Real-time distributed temperature measurement has been achieved through this sensor network, and it has shown great potential to be integrated into composites. 1 2

Influence of Interface Degradation on the Performance of Piezoelectric Actuators

An experimental and numerical study was performed to investigate the effects of interface debonding on the performance of piezoelectric (PZT) ceramic actuators for structural health monitoring (SHM) systems. Interface degradation of PZT actuators may occur over time during the in-service life of the structure compromising the performance and reliability of the SHM system. Energy losses and signal changes should be understood to guarantee the reliability of the SHM systems during the life-time of the structure. Here we present the first systematic study on the performance of PZT actuators with a partially degraded interface. The electro-mechanical coupling between PZT actuators and a hosting aluminium plate was found to vary with the interface debonding over a wide frequency range affecting the amplitude and phase of the actuator’s signal. A signal delay and an amplitude decrease were observed for: increasing debonding area, different debond shape, and location underneath the PZT actuators. Changes were found to be dependent on the actuation frequency with respect to the PZT resonance frequency. A spectral element-based code integrated with a coupled electro-mechanical field solver was used to verify the experimental results by simulating the propagation of ultrasonic Lamb waves in an aluminum plate with built-in PZT sensors/actuators.

A large area flexible expandable network for structural health monitoring

An investigation was performed to develop a flexible sensor network that can be stretched and expanded to cover structures with an order of magnitude larger than its original unexpanded size. The increasing need to cover large areas with a high number of sensors, networks, and electronic devices for structural health monitoring leads to this study. In this paper a flexible polymer with ultra- high stretching capability (linear expansions larger than 1000% the original length) is designed, fabricated and tested for sensor network applications. The stretchability of the polymer is achieved by engineering thousands of micronodes, which house the sensors and electronics, interconnected by extendable and flexible polymer microwires. The extendable microwires are the key element to perform uniform expansions of the network in all directions, to allow precise location of the nodes, to maximize the polymer expansion per unit area and to allow translation only of the nodes. With the proposed microwire design, a linear elongation wider than 1000% was achieved for a 256 nodes network, avoiding failure of the microwires and micronodes during fabrication and extension. It is believed that the proposed flexible, expandable polymer design is a cost-effective approach to integrate networks of thousands of sensors, actuators and electronic devices into large structures.

Functionalization of stretchable networks with sensors and switches for composite materials

An investigation was performed to develop appropriate techniques to design and fabricate (using complementary metal-oxide semiconductor/micro-electro-mechanical systems technologies) highly stretchable networks of distributed sensors and organic diodes that could be stretched, and surface-mounted or embedded into polymeric materials to cover an area several orders of magnitude larger than its original size. Both analysis and experiments were performed to validate the design and fabrication methods. The techniques sought to reduce stresses due to network expansion, and a new spin-coated fabrication process was developed to enable high-resolution features in the network. Networks with temperature sensors and piezoelectric sensors were fabricated and tested to demonstrate functionality in advanced composite materials that are common in aircraft.