The fingerprint effect describes the relationship between slip speed, fingerprint ridge spacing, and the frequency of vibrations created by the movement of a fingerprint across a surface. We have previously shown that the spacing between straight, parallel, evenly spaced ridges in fingerprint-like structures, and thus the vibrations produced by the fingerprint effect, are dependent on the orientation of the ridges with respect to the direction of movement. We also showed that, when ridge orientation is known, the fingerprint effect can be used to estimate slip speed in real-time. The physical processes behind the fingerprint effect also apply to the interaction between a surface and other, non-ridge, microstructures. It is, therefore, theoretically possible to use the fingerprint effect generated by these structures to estimate slip speed. However, it is first necessary to understand the nature of the fingerprint effect generated by these non-ridge structures. In this paper, we show that digitized structures, evenly spaced in columns and rows, have a more complex relationship to the fingerprint effect than ridges do. At most orientations, these structures produce vibrations amplified around four frequencies, each determined by a set of virtual ridges defined by the digitized structures. A sensor with$\mathbf{100}\ \boldsymbol{\mu} \mathbf{m}$tall,$\mathbf{150}\ \boldsymbol{\mu} \mathbf{m}$wide micropillars in evenly spaced rows and columns, with a spacing of$\mathbf{300}\ \boldsymbol{\mu} \mathbf{m}$center-to-center, is fabricated. This sensor is tested at angles between 0° and 90° by 15° increments. The results support our theoretical analysis.

The fingerprint effect, wherein vibrations are produced with frequencies related to the speed of a surface sliding across fingerprint ridges and the period of those ridges, has been studied for use in both slip detection and texture recognition. Here, we use a simple bioinspired sensor with parallel, straight, fingerprint-like ridges and a single ferroelectric ceramic transducer to show that the fingerprint effect is orientation dependent and that, if the orientation is known, it can be used to estimate slip speed. Our results, obtained at sliding speeds of 15 mm/s, 20 mm/s, and 25 mm/s and orientations from 0° – 90°, clearly demonstrate this dependence. Additionally, we use our results to run a simulation, using MATLAB software, of real-time slip speed estimation. The simulation shows that the fingerprint effect can be used for real-time slip-speed estimation.

This paper presents the fabrication, characterization and testing of bio-inspired synthetic dry adhesive fiber arrays. Fibers were fabricated via micromolding followed by spatula tip formation via dipping. Arrays of fibers with diameters between 28 mum and 57 mum and a height of 114 mum were fabricated with high uniformity on 6.25 cm2areas with up to 95% yield. Adaptation to uneven surfaces was observed with fiber elongations over 6 times the original height of the fiber. The unstructured sample exhibited 1.6 times as much adhesion as the fiber array sample for the flat punch indenter. However, fibrillar samples demonstrated up to 5.3 times as much adhesion as the unstructured sample for the hemispherical indenter. The fibrillar adhesive sample was implemented on a wall climbing robot which was able to carry itself and climb a distance on a painted wall and wood door.

One of the primary impediments to building ensembles of modular robots is the complexity and number of mechanical mechanisms used to construct the individual modules. As part of the Claytronics project - which aims to build very large ensembles of modular robots - we investigate how to simplify each module by eliminating moving parts and reducing the number of mechanical mechanisms on each robot by using force-at-a-distance actuators. Additionally, we are also investigating the feasibility of using these unary actuators to improve docking performance, implement intermodule adhesion, power transfer, communication, and sensing. In this paper we describe our most recent results in the magnetic domain, including our first design sufficiently robust to operate reliably in groups greater than two modules. Our work should be seen as an extension of systems such as Fracta [9], and a contrasting line of inquiry to several other researchers' prior efforts that have used magnetic latching to attach modules to one another but relied upon a powered hinge [10] or telescoping mechanism [12] within each module to facilitate self-reconfiguration.

We propose a demonstration of extremely scalable modular robotics algorithms developed as part of the Claytronics Project (http://www-2.cs.cmu.edu/~claytronics/), as well as a demonstration of proof-of-concept prototypes. Our effort envisions multi-million-module robot ensembles able to morph into three-dimensional scenes, eventually with sufficient fidelity so as to convince a human observer the scenes are real. Although this work is potentially revolutionary in the sense that it holds out the possibility of radically altering the relationship between computation, humans, and the physical world, many of the research questions involved are similar in flavor to more mainstream systems research, albeit larger in scale. For instance, as in sensor networks, each robot will incorporate sensing, computation, and communications components. However, unlike most sensor networks each robot will also include mechanisms for actuation and motion. Many of the key challenges in this project involve coordination and communication of sensing and actuation across such large ensembles of independent units.