Publications - Conference Paper

The computation of skin forces and deformations for tactile rendering requires an accurate model of the extremely nonlinear behavior of the skin. In this work, we investigate the characterization of fingermechanics with the goal of designing accurate nonlinear models for tactile rendering. First, we describe a measurement setup that enables the acquisition of contact force and contact area in the context of controlled finger indentation experiments. Second, we describe an optimization procedure that estimates the parameters of strain-limiting deformation models that match best the acquired data. We show that the acquisition setup allows the measurement of force and area information with high repeatability, and the estimation method reaches nonlinear models that match the measured data with high accuracy.

Effective execution of a manipulation task using prosthetic or robotic hands requires that the motion and the impedance profiles of the fingers be appropriately commanded. This, however, brings some design and control challenges regarding the individual planning and realization of the finger motion and stiffnesstrajectories. It appears that the central nervous system solves for this complexity in an effective and coordinated manner which has been well-recognized under the concept of hand synergies. While the exploitation of this concept in kinematic coordinates has lead to the development of several successful robotic designs and control strategies, its extension to dynamic coordinates, such as coordinated stiffening of the fingers, remains to be investigated. Indeed, in this study we provide preliminary evidence on the existence of such coordinated stiffening patterns in human fingers and establish initial steps towards a real-time and effective modelling of the finger stiffness in a tripod grasp. To achieve this goal, the endpoint stiffness of the thumb, index and middle fingers of five healthy subjects are experimentally identified and correlated with the electromyography (EMG) signals recorded from a dominant antagonistic pair of the forearm muscles. Our findings suggest that: i) the magnitude of thestiffness ellipses at the fingertips grows in a coordinated way, subsequent to the co-contraction of the forearm muscles; ii) the length of the ellipses' axes appears to have a nearly linear relationship with the co-contraction level of the antagonistic muscle pair.

Decentralized coordination of multi-agents requires that every agent reliably and efficiently disseminates its state to neighbours
through a wireless network. If dissemination is unreliable, safety issues may ensue. Unfortunately, the broadcast service of
wireless network is efficient but unreliable (e. g., IEEE 802.11). The Neighbourhood Monitoring Protocol (NMP) [1] is an efficient
and scalable protocol that assures a reliable state dissemination between mobile agents, under some conditions of channel
utilization. NMP runs on top of IEEE 802.11. In this paper we evaluate NMP with a specific decentralized collision avoidance
algorithm based on the GRP policy [2]. The algorithm is particularly challenging because it accommodates an arbitrary number
non-holonomic agents. We show that NMP allows the system to scale well and provides a very high state delivery ratio even if it
operates on the unreliable broadcast service like 802.11. Doing so, NMP assures the correct state information to the collision
avoidance algorithm.

More meaningful in-vitro models which simulate the physiological conditions of native tissue are becoming essential in the pharmaceutical field, for early and rapid screening of drug candidates. Here, we describe a multi-organ-on-plate system based on single and double flow mini bioreactor modules for dynamic in-vitro studies of intestinal drug absorption, drug metabolism and more relevant toxicity studies. The double flow module for membrane culture was firstly characterized using computational fluid dynamic models and measurements of pressure gradients, in order to indentify the optimal flow rates for maximizing the passage of solutes through the membrane. Then, cell culture experiments were performed with fully differentiated Caco-2 cells seeded on the semi-permeable membrane as a dynamic model of the intestinal epithelium, connected to a single flow chamber with metabolically competent human upcyte® hepatocytes (Medicyte GmbH, Germany) seeded on a 3D collagen cryogel. First we assessed the role of flow in modulating the passage of compounds across the epithelial barrier. Then toxicity tests were performed by administering different concentrations of hepatotoxic compounds (i.e. Diclofenac, Nimesulide, industrial nanoparticles) in the apical compartment of the MB, compared the data with cell cultures in transwells. Our results show: i) the presence of flow significantly increases translocation of all molecules tested across the membrane, ii) flow conditioned Caco-2 cells are more permeable to small hydrophilic compounds, despite having high TEER values iii) although they display higher levels of phenotypic markers (tight junctions, albumin expression etc), cells in the system are more susceptible to drug induced toxicity. In conclusion, the multi-organ-on-plate system predicts drug adsorption and toxicity better than traditional cell cultures and could be used to reduce, refine and eventually replace animal tests.