Robots are starting to transition from the confines of the manufacturing floor to homes, schools, hospitals, and highly dynamic environments. As, a result, it is impossible to foresee all the probable operational situations of robots, and preprogram the robot behavior in those situations. Among human-robot interaction technologies, haptic communication is an intuitive physical interaction method that can help define operational behaviors for robots cooperating with humans. Multimodal robotic skin with distributed sensors can help robots increase perception capabilities of their surrounding environments.
Electro-Hydro-Dynamic (EHD) printing is a flexible multi-modal sensor fabrication method because of its direct printing capability of a wide range of materials onto substrates with non-uniform topographies. In past work we designed interdigitated comb electrodes as a sensing element and printed piezoresistive strain sensors using customized EHD printable PEDOT:PSS based inks. We formulated a PEDOT:PSS derivative ink, by mixing PEDOT:PSS and DMSO. Bending induced characterization tests of prototyped sensors showed high sensitivity and sufficient stability.
In this paper, we describe SkinCells, robot skin sensor arrays integrated with electronic modules. 4x4 EHD-printed arrays of strain sensors was packaged onto Kapton sheets and silicone encapsulant and interconnected to a custom electronic module that consists of a microcontroller, Wheatstone bridge with adjustable digital potentiometer, multiplexer, and serial communication unit. Thus, SkinCell’s electronics can be used for signal acquisition, conditioning, and networking between sensor modules. Several SkinCells were loaded with controlled pressure, temperature and humidity testing apparatuses, and testing results are reported in this paper.
In order to control neural prosthetics by recording signals from peripheral nerves with the required specificity, high density electrode arrays that can be easily implanted on very small peripheral nerves (50μm-500μm) are needed. Interfacing with these small nerves is surgically challenging due to their size and fragile nature. To address this problem, a Flexible MicroChannel Electrode Array for interfacing with small diameter peripheral nerves and nerve fascicles was developed. The electrochemical characterization and electrophysiological recordings from the common peroneal nerve of a rat are presented along with demonstration of the surgical ease-of-use of the array.
Robotic skins with multi-modal sensors are necessary to facilitate better human-robotic interaction in non-structured
environments. Integration of various sensors, especially onto substrates with non-uniform topographies, is challenging
using standard semiconductor fabrication techniques. Printing is seen as a technology with great promise that can be
used for sensor fabrication and integration as it may allow direct printing of different sensors onto the same substrate
regardless of topology. In this work, we investigate Electro-Hydro-Dynamic (EHD) printing, a method that allows
printing of micron-sized features with a wide range of materials, for fabricating pressure sensor arrays using Poly(3,4-
ethylenedioxythiophene):Polystyrene Sulfonate (PEDOT:PSS). Fabrication of such sensors has been achieved by prepatterning
gold or platinum metallized interdigitated comb electrode arrays on a polyimide substrate, with three custom
made PEDOT:PSS based inks printed directly onto the electrode arrays. These three inks include a formulation of
PEDOT:PSS and NMP; PEDOT:PSS, PVP, and NMP; and PEDOT:PSS, PVP, Nafion, and NMP. All these inks were
successfully printed onto sensor elements. The initial results of bending-induced strain tests on the fabricated sensors
display that all the inks are sensitive to strain. This confirms their suitability for pressure and strain sensor applications;
however, the behavior of each ink; including sensitivity, linearity, and stability; is unique to the type.
Human-robot interaction can be made more sophisticated and intuitive if the entire body of a robot is covered with multimodal sensors embedded in artificial skin. In order to efficiently interact with humans in unstructured environments, robotic skin may require sensors such as touch, impact, and proximity. Integration of various types of sensors into robotic skin is challenging due to the topographical nature of skin. Printing is a promising technology that can be explored for sensor integration as it may allow both sensors and interconnects to be directly printed into the skin. We are developing Electrohydrodynamic (EHD) inkjet printing technology in order to co-fabricate various devices onto a single substrate. Using strong applied electrostatic forces, EHD allows the printing of microscale features from a wide array of materials with viscosities ranging from 100 to 1000cP, highly beneficial for multilateral integration. Thus far we have demonstrated EHD’s capability at printing patterns of Poly(2,3-dihydrothieno-1,4-dioxin)-poly(styrenesulfonate) for pressure sensor applications, generating patterns with modified commercial photoresist for mask-less lithography, and obtaining ZnO microstructures for direct device printing. Printed geometries range from a few tens of microns to millimeters. We have used inks with viscosities ranging from 230 to 520cp and from non-conductive to 135μS/cm. These results clearly show that the EHD is a promising multi-material printing platform and would be an enabling technology that can be used to co-fabricate various devices into robotic skin.
This paper presents an implementation of a bubble actuator array (BAA) based active robotic skin, a modular system, onto existing low cost robotic end-effectors or prosthetic hands for conformal grasping of objects. The active skin is comprised of pneumatically controlled polyurethane rubber bubbles with overlaid sensors for feedback control. Sensor feedback allows the BAA based robotic skin to conformally grasp an object with an explicit uniform force distribution. The bubble actuator array reported here is capable of applying up to 4N of force at each point of contact and tested for conformally grasping objects with a radius of curvature up to 57.15mm. Once integrated onto a two-finger gripper with one degree of freedom (DOF), the active skin was shown to reduce point of contact forces of up to 50% for grasped objects.
We present the fabrication and testing of a silicon carbide balanced mass double-ended tuning fork that survives harsh environments without compromising the device strain sensitivity and resolution bandwidth. The device features a material stack that survives corrosive environments and enables high-temperature operation. To perform high-temperature testing, a specialized setup was constructed that allows the tuning fork to be characterized using traditional silicon electronics. The tuning fork has been operated at 600°C in the presence of dry steam for short durations. This tuning fork has also been tested to 64,000 G using a hard-launch, soft-catch shock implemented with a light gas gun. However, the device still has a strain sensitivity of 66 Hz/µ and strain resolution of 0.045 µ in a 10-kHz bandwidth. As such, this balanced-mass double-ended tuning fork can be used to create a variety of different sensors including strain gauges, accelerometers, gyroscopes, and pressure transducers. Given the adaptable fabrication process flow, this device could be useful to microelectromechanical systems (MEMS) designers creating sensors for a variety of different applications.
The residual strain of amorphous and polycrystalline SiC films deposited using a single precursor 1,3-disilabutane is characterized as a function of deposition temperature ranging from 700 to 850°C. SiC microstrain gauges and cantilever beam arrays fabricated by micromachining are employed to characterize directly the average residual strain and strain gradient. The residual strain of SiC films changes from compressive to tensile as the deposition temperature increases. The strain gradient is also found to depend on the deposition temperature, and can be adjusted between positive and negative values to fabricate flat, curling-up, and curling-down micromechanical structures.
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