Application of Piezoelectric actuated MEMS for ultra high neurological surgery
The precision is highly important. The precision problem can be controlled by decreasing the size of the robotic arm to the suitable controllable size. Still, as for power sources, the motor vibration and transmission can cause unnecessary movement, endangering the patient. MEMS is potential solution such that it can provide a surgical tool with minimum human intervention. Micro and non-robotic arms application goes beyond medical application and it prove its validity for many challenging applications, so such mechanisms can make the manufacturing of Nano devices, and electronics, simpler. Nano scale crafted electronics are used in consumer computers, and smartphones.
Introducing considerable simple design, with high precision nano robotics can be a useful tool to decrease the scale of nano scale crafting. For example, moving atoms using Scanning Tunneling Microscope (STM) can be a systematic production process for Nano crafting. MEMS have several challenges which also the advantages of such systems. First is the spacial challenge (small size manufacturing). So, the process of making small complex linking mechanisms, gears, etc. is a difficult task, add to that the cost factor, so for high quality micro and Nano devices, even with relatively simple set of gears, moving joints and links, needs highly specialized processes and expensive machines. Compliance mechanism as a way of design simple ,single-part mechanism that achieve the task such as clamping by applying currents on it. Within the advancement in material processing, many techniques been advanced for cheaper micro and Nano structure manufacturing such as lithography and CVD. For example, Toledo et al at 2017 successfully built compliant mechanism using Silicon on insulator base actuator. Piezoelectric materials are anisotropic dielectrics. electricity is varying with external electric and/or force field that is applied to the piezoelectric structure. It forms an electric dipole. Because of dielectric polarization, different charges react positively proportional to the electric field that applied. The polarization can be formulated in terms dipole moments. When a piezoelectric force field act on the piezoelectric material, the topology of the atomic structure of the crystal deviate in a way creating effective dipoles, and a dipole moment is formed. And because of anisotropic properties, when a piezoelectric material is loaded electrically then the electrical dipoles appear only after electrical or mechanical load. Electro-elasticity deals with such phenomenon. The piezoelectric effect is presented as the density electric moment (P) as shown in equation
Add alt text
Here, d is the piezoelectric modulus associated to stress tensor. Related strain be
Add alt text
The electro-mechanical coupling can be derived from Maxwell’s. the total strain energy of the electro-mechanical system is given as
Add alt text
The derivative of energy equation in terms of strain gives the designated stress, and the derivative in terms of electric field vector gives the component of electrically induced displacement.
Add alt text
Add alt text
Designing micro electro-mechanical systems based gripper is challenging task specially with introducing accurate and tactile gripping. Tactile gripping is important aspect of designing ultra high positioning systems. Non parametric optimization is a powerful methodology for structural design. topology optimization is on of the important methodology of the non parametric tendency of structures and machine design and optimization.. Topology optimization (TO) be designed method based on a mathematical scheme to introduce non-existence material within design space to get designer properties such as light weight or certain mechanical properties.Topology optimization shows good results of designing single structure that can-do movement by applying action in desired points. Compliant mechanisms that is designed using topology optimizations, have no bearing, and do not need complicated links attachment, so it eases the way of making. Making compliant mechanism of piezoelectric will offer self-actuation by applying potential, so it will not need complex mechanism to derive and apply forces.
