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In the development of surgical technologies, one of the challenges in their initial validation has been the creation of accurate bench-top tissue phantoms. Tissue phantoms made of elastomeric material have fixed mechanical properties and are not able to increase in size, so they cannot mimic growth process or change in mechanical properties of their real counterparts. In this work we present a novel real-time soft tissue simulator aimed at testing the in vivo dynamic behavior of robotic implants. The simulator is capable of reproducing mechanical properties of the biological tissue, e.g. viscoelasticity, as well as its metabolism, being able to grow up to 260 mm. A control strategy based on impedance control enables the simulation of changing mechanical properties in real-time, in order to recreate conditions such as fibrosis or tissue scarring. We finally show the platform in use with a soft implant. The electric actuation in conjunction with the 500 Hz control loop frequency guarantees fast and accurate response. We believe our platform has the potential to reduce the need for in vivo preclinical studies and shorten the path to clinical experimentation.

In this study, a novel robotic bioreactor is presented with capabilities of closed-loop control of force and displacement applied to a tissue scaffold and tissue scaffold stiffness calculation. These characteristics bring the potential of a robotic bioreactor that can optimize the mechanical properties of tissue constructs in order for them to match those of native tissues. Custom position and force control signals are designed to maintain a steady tensioning of the tissue scaffold while the latter one's mechanical properties evolve in time. We propose a simple model to support the hypothesis that the stiffness of a cell-seeded scaffold increases over time, and thus force control signals need to be adjusted accordingly. The robotic bioreactor is able to measure the stiffness of a scaffold sample relatively accurately, with an average standard deviation of 0.2N/mm. The combination of accurate stiffness measurements and a closed-loop control system equips the robotic bioreactor with the fundamental requirements to achieve stiffness based force control in future in vitro experiments, and thus to a tissuescaffold responsive technology for advanced tissue engineering.

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This article investigates an inverted pendulum on a mobile cart (mobile inverted pendulum) controlled via a programmable logic controller and actuated by a double-acting pneumatic cylinder. The study is conducted both theoretically, by modeling and simulating the entire system, and experimentally, using a specially developed test bench. Four low-cost 2/2 proportional valves are used for cylinder control. The control architecture consists of two nested control loops with proportional–integral–derivative compensators. To reduce cost, a programmable logic controller was used to manage both the system control and data acquisition. The results of the simulations carried out using linear and nonlinear models of the system were validated by comparison with those obtained experimentally.