# A State-of-the-Art Review on Robots and Medical Devices Using Smart Fluids and Shape Memory Alloys
## 5 Conclusions and Future Direction  
This topical review presents state-of-the-art developments of robotic applications using smart materials. Smart materials used for robotic applications include electro-rheological (ER) fluids, magneto-rheological (MR) fluids, and shape memory alloys (SMAs). As reviewed, these smart materials can be effectively used as actuators for various types of robots, but there exist still many material and technical limitations for practical implementation. Both ERF and MRF are very effective to devise special robots such as leg robot in which unwanted vibrations need to be controlled in real time. To successfully realize those special robots in practical environment, the higher level of the field-dependent yield stress, the higher robustness to impurities, the wider temperature range, the less abrasiveness and wear properties, and the prevention of particle sedimentation are essentially required to be resolved or improved. Bio-inspired small-scale soft robotics using SMAs are very promising candidates for practical use because of their artificial muscle properties with large strain variation. However, in order to apply SMAs to robots, the narrow bandwidth issue associated with the asymmetric actuation property should be first resolved. Moreover, continuous improvement on their controllability, stability, and large actuation force are still essential to be ensured for future-oriented robot applications associated with SMA actuator. This review article has covered recent advances and trends on robotic applications using diverse smart materials.  
The words representing future robots will be 'artificial intelligence' and 'natural mimicking', and the implementation of natural mimicking is proceeding in the form of soft robotics. Soft robotics is a newly emerging field of robot research. It is expected that friendly human-robot interaction will be obtained based on inherent soft characteristics. The soft robots can be adopted to their surroundings actively and can mimic the function of biological systems such as octopus leg and human muscles. The final goal of soft robotics is the integration of soft actuators, sensors, controls and power source without any rigid part. Soft materials, actuating mechanisms using the materials, and fabrication methods such as 3D printing have been extensively studied. However, there are still many challenges in the field of soft robotics. From the material aspect of the sensor and the actuator, soft and smart materials, such as shape memory alloys, shape memory polymers, electro-rheological fluids, electro-rheological elastomers, magneto-rheological fluids, magneto-rheological elastomers, and electro-active polymers (EAPs) are very important part for the successful development of soft robots. Smart materials will change the definition of a robot and the relationship between robot and human.  
However, it should be noted here that the development of a new class of smart materials, which can be optimally and adaptively applicable to various robots, is still an on-going research issue. Continuous advances in the synthesis of smart materials are likely to motivate the creativity of researchers seeking to harness these materials for robotic applications. Finally, this review article provides very useful information on the potential research opportunities and emerging technologies using smart materials for the innovative robots of the future.  
Figure 12: SMA wire-based end-effector for minimally invasive surgery [91].  
**Author Contributions:** [PERSON] as a corresponding author takes the primary responsibility for this article. [PERSON] and [PERSON] drafted the manuscript, and all co-authors reviewed.  
**Funding:** This research was funded by INHA IST-NASA Deep Space Exploration Joint Research Center (NRF-2017K1A4A3013662).  
**Conflicts of Interest:** The authors declare no conflicts of interest.