RESUMEN
To get an optimal product of orthopaedic implant or regenerative medicine needs to follow trial-and-error analyses to investigate suitable product's material, structure, mechanical properites etc. The whole process from in vivo tests to clinical trials is expensive and time-consuming. Computational model is seen as a useful analysis tool to make the product development. A series of models for simulating tissue engineering process from cell attachment to tissue regeneration are reviewed. The challenging is that models for simulating tissue engineering processes are developed separately. From cell to tissue regeneration, it would go through blood injection after moving out the defect; to cell disperse and attach on the scaffold; to proliferation, migration and differentiation; and to the final part-becoming mature tissues. This paper reviewed models that related to tissue engineering process, aiming to provide an opportunity for researchers to develop a mature model for whole tissue engineering process. This article focuses on the model analysis methods of cell adhesion, nutrient transport and cell proliferation, differentiation and migration in tissue engineering. In cell adhesion model, one of the most accurate method is to use discrete phase model to govern cell movement and use Stanton-Rutland model for simulating cell attachment. As for nutrient transport model, numerical model coupling with volume of fluid model and species transport model together is suitable for predicting nutrient transport process. For cell proliferation, differentiation and migration, finite element method with random-walk algorithm is one the most advanced way to simulate these processes. Most of the model analysis methods require further experiments to verify the accuracy and effectiveness. Due to the lack of technology to detect the rate of nutrient diffusion, there are especially few researches on model analysis methods in the area of blood coagulation. Therefore, there is still a lot of work to be done in the research of the whole process model method of tissue engineering. In the future, the numerical model would be seen as an optimal way to investigate tissue engineering products bioperformance and also enable to optimize the parameters and material types of the tissue engineering products.
Asunto(s)
Ingeniería de Tejidos , Diferenciación Celular , Movimiento Celular , Proliferación Celular , Simulación por ComputadorRESUMEN
BACKGROUND: Surgical robotic systems have been proven to be accurate and dexterous during minimally invasive surgery (MIS). However, single incision laparoscopic surgery (SILS) requires more compact robotic arms with sufficient dexterity and output. METHODS: A shape memory alloy (SMA)-actuated instrument was adopted to assist operations. The instrument fixed at the slave site had three degrees of freedom (DOFs) and was driven by SMA wires, pitch, yaw, and grip, with an 8 mm diameter; a passive hydraulic support mechanism was placed in vitro. RESULTS: In vitro, the maximum force, velocity and accuracy were proven to be sufficient for medical application. In an animal study, the system was inserted into the abdomen; three more generic constraints were tested: medical gesture, safety, and implementation. CONCLUSIONS: The robot was feasible and safe for multi-angle monitoring, grasping, and holding an organ. The SMA-actuated system was accurate and dexterous with minimal system volume.
Asunto(s)
Procedimientos Quirúrgicos Robotizados/instrumentación , Aleaciones , AnimalesRESUMEN
With the progress of miniaturization, shape memory alloy (SMA) actuators exhibit high energy density, self-sensing ability and ease of fabrication, which make them well suited for practical applications. This paper presents a self-sensing controlled actuator drive that was designed using antagonistic pairs of SMA wires. Under a certain pre-strain and duty cycle, the stress between two wires becomes constant. Meanwhile, the strain to resistance curve can minimize the hysteresis gap between the heating and the cooling paths. The curves of both wires are then modeled by fitting polynomials such that the measured resistance can be used directly to determine the difference between the testing values and the target strain. The hysteresis model of strains to duty cycle difference has been used as compensation. Accurate control is demonstrated through step response and sinusoidal tracking. The experimental results show that, under a combination control program, the root-mean-square error can be reduced to 1.093%. The limited bandwidth of the frequency is estimated to be 0.15 Hz. Two sets of instruments with three degrees of freedom are illustrated to show how this type actuator could be potentially implemented.