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Not AvailableThis paper reports on thermally switchable tethers that control the rapid release of strained microhooks from silicon substrates. Applications include automated microassembly of electronic circuits using clips that grasp microscale (<200 micron diameter) conductive fibers, as well as assembly of microdevices onto heat-sensitive materials by grasping. We developed an integrated, photoresist-based thermal release structure that allows the first direct observations of the release process outside the etch chamber. High speed camera video (4200 frames/s) shows the cantilevers release in an order determined by thermal diffusion, with groups of ~ 1200 micron long cantilevers releasable at 100 Hz. Side-view video is analyzed to show that the height of the graspable region is approximately half the hook length. The thermally isolated release method prevents the microhooks from heating, making it potentially useful for grasping heat-sensitive polymeric and biological materials. 

This paper reports on the steps that happen after the release of strained microhooks from silicon substrates. The application is automated microassembly of electronic circuits using clips that grasp microscale (< 200 micron diameter) conductive fibers. We developed an integrated, photoresist-based thermal release structure that allows the first direct observations of the release process outside the etch chamber. High speed camera video (4200 frames/s) shows the cantilevers release in an order determined by thermal diffusion, with groups of ~1200 micron long cantilevers releasable at 100 Hz. Side-view video is analyzed to show that the height of the graspable region is approximately half the hook length. 

Packaging electronic devices within electronic textiles and fibrous substrates requires an understanding of how fibers interact with circuit components in different operating conditions. In this paper, we use microeletromechanical (MEMS) devices to put devices in electrical contact with fine wires. We characterize the electronic properties of MEMS-to-wire contacts and discuss general guidelines for optimizing the design of these grippers and potential MEMS-based circuits. We then demonstrate how these grippers can act as non-rigid circuit components that effectively transfer power to devices such as LEDs. Analysis shows that our grippers are suitable conductors (under 150 Ohms) under standard operating temperatures (25-100 deg. C) with potential for use as sensors for current overflow or temperature. Methods such as parylene deposition and silver epoxy to stabilize MEMS performance are briefly discussed and explored. 

Electronic textile (E-textile) research requires an understanding of the mechanical properties of fabric substrates used to build and support electronics. Because fibers are often non-uniform and fabrics are easily deformed, locating fiber junctions on the irregular surface is challenging, yet is essential for packaging electronics on textiles at the resolution of single fibers that deliver power and signals. In this paper, we demonstrate the need to identify fiber junctions in a task where microelectromechanical structures (MEMS) are integrated on fabrics. We discuss the benefits of fiber-aligned placement compared with random placement. Thereafter we compare three image processing algorithms to extract fiber junction locations from sample fabric images. The Hough line transform algorithm implemented in MATLAB derives line segments from the image to model the fibers, identifying crossings by the intersections of the line segments. The binary image analysis algorithm implemented in MATLAB searches the image for unique patterns of 1s and 0s that represent the fiber intersection. The pattern matching algorithm implemented in Vision Assistant - LabVIEW, uses a pyramid value correlation function to match a reference template to the remainder of the fabric image to identify the crossings. Of the three algorithms, the binary image analysis method had the highest accuracy, while the pattern matching algorithm was fastest. 

ABSTRACT This paper discusses new components and approaches to make stretchable optical fiber sensors better meet the power and washability requirements of wearables. First, an all-polymer quick connector allows the light source and photosensor to be quickly detached for washing. Second, the paper investigates the possibility of driving the sensors using ambient light instead of an onboard light source. While optical strain sensors and touch sensors have advantages over electronic ones in wet environments, and the intrinsic stretchability of the fibers is useful for soft robotics and highly conformal wearables, the typical light-emitting diode (LED) light source consumes more power than an electronic resistive or capacitive strain sensor. In this work, ambient light of uniform but unknown intensity is demonstrated to drive an elastomeric optical touch sensor in a differential configuration.