Dana D. Damian

Slip Speed Feedback for Grip Force Control

Grasp stability in the human hand has been resolved by means of an intricate network of mechanoreceptors integrating numerous cues about mechanical events, through an ontogenetic grasp practice. An engineered prosthetic interface introduces considerable perturbation risks in grasping, calling for feedback modalities that address the underlying slip phenomenon. In this study, we propose an enhanced slip feedback modality, with potential for myoelectric-based prosthetic applications, that relays information regarding slip events, particularly slip occurrence and slip speed. The proposed feedback modality, implemented using electrotactile stimulation, was evaluated in psychophysical studies of slip control in a simplified setup. The obtained results were compared with vision and a binary slip feedback that transmits on-off information about slip detection. The slip control efficiency of the slip speed display is comparable to that obtained with vision feedback, and it clearly outperforms the efficiency of the on-off slip modality in such tasks. These results suggest that the proposed tactile feedback is a promising sensory method for the restoration of stable grasp in prosthetic applications.

Soft-matter capacitive sensor for measuring shear and pressure deformation

We introduce a soft-matter sensor that measures elastic pressure and shear deformation. The sensor is composed of a sheet of elastomer that is embedded with fluidic parallel-plate capacitors. When the elastomer is pressed or sheared, the electrodes of the embedded capacitors come closer together or slide past each other, respectively, leading to a change in capacitance. The magnitude and direction of the shear deformation is established by comparing the change in capacitance of multiple embedded capacitors. We characterize the soft sensor theoretically and experimentally. Experiments indicate that 2D shear and pressure deformation can be discriminated with approximately 500 μm and 5 kPa sensitivity, respectively. The theoretical predictions and experimental results are in reasonable agreement. We also propose improvements to the fabrication method in order to facilitate integration of soft-matter sensing with wearable electronics.

Ingestible, controllable, and degradable origami robot for patching stomach wounds

Developing miniature robots that can carry out versatile clinical procedures inside the body under the remote instructions of medical professionals has been a long time challenge. In this paper, we present origami-based robots that can be ingested into the stomach, locomote to a desired location, patch a wound, remove a foreign body, deliver drugs, and biodegrade. We designed and fabricated composite material sheets for a biocompatible and biodegradable robot that can be encapsulated in ice for delivery through the esophagus, embed a drug layer that is passively released to a wounded area, and be remotely controlled to carry out underwater maneuvers specific to the tasks using magnetic fields. The performances of the robots are demonstrated in a simulated physical environment consisting of an esophagus and stomach with properties similar to the biological organs.

Artificial ridged skin for slippage speed detection in prosthetic hand applications

The human hand is one of the most complex structures in the body, being involved in dexterous manipulation and fine sensing. Traditional engineering approaches have mostly attempted to match such complexity in robotics without sufficiently stressing on the underlying mechanisms that its morphology encodes. In this work, we propose an artificial skin able to encode, through its morphology, the tactile sense of a robotic hand, characteristic to slippage events. The underlying layout consists of ridges and allows slippage detection and the quantification of slippage speed. Such encoding of slippage signal becomes suitable for relaying tactile feedback to users in prosthetic applications. This approach emphasizes the importance of exploiting morphology and mechanics in structures for the design of prosthetic interfaces.

Artificial Tactile Sensing of Position and Slip Speed by Exploiting Geometrical Features

Rich information about artificial grasps can be obtained using tactile sensing arrays. However, the complexity of the integration and computation inherent to tactile sensor arrays limits their applicability for prosthetic manipulators. We present an artificial ridged skin that detects the position and speed of a slipping object using a single force sensor. The artificial skin features parallel ridges arranged in a nonuniform configuration. An evolutionary algorithm generates distributions of ridges evaluated by the accuracy and resolution of detecting the position and speed of a slipping object. Slip experiments on real skins featuring ridge distributions generated by the evolutionary algorithm show that ridge arrangement is critical for an improved sensing of object position and slip speed. We report ridge patterns that detect object position and speed with errors as low as 10% at slip speeds of up to 60 mm/s. The artificial skin has an average speed sensing resolution of 10 mm/s, an average position sensing resolution of 15 mm, and is robust to various grip conditions, e.g., speed variation, object weight, and contact area. By exploiting the geometrical features of the artificial skin, enhanced tactile information is acquired. The concept opens a promising avenue for robust and energy-efficient tactile sensing systems.

Robotic implant to apply tissue traction forces in the treatment of esophageal atresia

This paper introduces robotic implants as a novel class of medical robots in the context of treating esophageal atresia. The robotic implant is designed to apply traction forces to the two disconnected esophageal segments to induce sufficient growth so that the two ends can be joined together to form a functioning esophagus. In contrast to the current manual method of externally applying traction forces, the implant offers the potential to avoid prolonged patient sedation and to substantially reduce the number of X-rays required. A prototype design is presented along with evaluation experiments that demonstrate its capabilities to apply traction forces to ex vivo esophageal tissues.

In vivo tissue regeneration with robotic implants

A robotic implant for inducing tissue growth in tubular organs is demonstrated through esophageal lengthening in swine. Robots that reside inside the body to restore or enhance biological function have long been a staple of science fiction. Creating such robotic implants poses challenges both in signaling between the implant and the biological host, as well as in implant design. To investigate these challenges, we created a robotic implant to perform in vivo tissue regeneration via mechanostimulation. The robot is designed to induce lengthening of tubular organs, such as the esophagus and intestines, by computer-controlled application of traction forces. Esophageal testing in swine demonstrates that the applied forces can induce cell proliferation and lengthening of the organ without a reduction in diameter, while the animal is awake, mobile, and able to eat normally. Such robots can serve as research tools for studying mechanotransduction-based signaling and can also be used clinically for conditions such as long-gap esophageal atresia and short bowel syndrome.

Electromagnetically driven elastic actuator

Elastic and active elements will play a leading role in the development of dexterous and compliant robots. We present the fabrication of an elastic functional structure with ferromagnetic properties capable of producing compressive stress and strain in the presence of magnetic fields. The elastic structure consists of a mixture of a soft elastomer and 99% pure iron powder. The magnetic and elastic properties of the material were modeled and investigated based on the principles of electromagnetism. These elastic actuators reach up to approximately -2700 N/m2 stress and achieve a strain of approximately 17% when embedded in a solenoid coil. The elastic actuators are promising for use as muscle-like structures while they provide softness in interaction.

An automated metrics set for mutual adaptation between human and robotic device

In rehabilitation robotics, a strong coupling between human and robot entails high requirements for achieving mutual adaptation. The latter underlies the acceptance of the robotic device as an extension of the human body and promotes an efficient collaboration. We present automated metrics for quantifying models of human-robot interaction and the mutual adaptation based on the pattern of informational flow between the two participants in the interaction. These methods allow the robotic device to gain the ability to score the mutual adaptation and to implement strategies for increasing it, fostering the human-centered robot autonomy in rehabilitation robotics.

The role of quantitative information about slip and grip force in prosthetic grasp stability

Abstract Prosthetic hands introduce an artificial sensorimotor interface between the prosthesis wearer and the environment that is prone to perturbations. We analyze theoretically and evaluate psychophysically the performance in stable grip control in conditions of physical grasps perturbation, such as object slip. Simulation results suggest that user-centered stable grasp control depends on two primal user parameters: reaction time to slip and grip force intensity. Experiments with human users indicate that a user’s response time can be controlled by relaying information about the speed of the slipping object, while minimal grip force intensity can be adjusted with information about grip force at the onset of the slip. Based on our theoretical and experimental findings, we propose a stable grasp control method for prosthetic hands.