Research on vacuumgripper based on fuzzy control for micromanipulators

This paper presents a vacuum gripper （as an actuator of an intelligent micromanipulator） for micro objects （with a diameter of 100 - 300μm） assembly tasks. The gripper is composed of a vacuum unit and a control unit. The vacuum unit with a proportional valve and a pressure sensor, and the control unit with a PC ＋ MCU two-layered control architecture are designed. The mechanical structure, workflow and major programs of the micro-gripper are presented. This paper discusses the major components of the adhesion force acting on micro objects. Some equations of the operation conditions m three phases of pick, hold and place are derived by mechanics analysis. The pneumatic system＇s pressure loss is inevitable. There are some formulas for calculating the amount of the pressure loss, but parameters in formulas are diffficult to be quantified and evaluated. To control the working pressure accurately, a pressure controller based on fuzzy logic is designed. With MATLAB＇s fuzzy logic toolbox, simulation experiments are performed to validate the performance of the fuzzy PD controller. The gripper is characterized by a steady and reliable performance and a simple structure, and it is suitable for handling micro objects with a sub-millimeter size.

Handmade cloning:recent advances,potential and pitfalls

Handmade cloning （HMC） is the most awaited, simple and micromanipulator-ffee version of somatic cell nuclear transfer （SCNT）. The requirement of expensive micromanipulators and skilled expertise is eliminated in this technique, proving it as a major revolution in the field of embryology. During the past years, many modifications have been incorporated in this technique to boost its efficiency. This alternative approach to micromanipulator based traditional cloning O-C） works wonder in generating comparable or even higher birth rates in addition to declining costs drastically and enabling cryopreservation. This technique is not only applicable to intraspecies nuclear transfer but also to interspecies nuclear transfer （iSCNT） thus permitting conservation of endangered species. It also offers unique possibilities for automation of SCNT which aims at production of transgenic animals that can cure certain human diseases by producing therapeutics hence, providing a healthier future for the wellbeing of humans. The present review aims at highlighting certain aspects of HMC including recent advancements in procedure and factors involved in elevating its efficiency besides covering the potentials and pitfalls of this technique

Release Method of Microobjects Based on Piezoelectric Vibration

A release method of microobjects is presented based on the piezoelectric vibration.To achieve an effective release,the piezoelectric vibration is added to overcome adhesion force happened in the microoperation.This technique employs inertia force to overcome adhesion force,thereby achieving 90%repeatability with a releasing accuracy of 4± 0.5μm,which was experimentally quantified through the manipulation of 20—80μm polystyrene spheres under an optical microscope.Experimental results confirmed that this adhesion control technique was independent of substrate.Theoretical analyses were conducted to understand the releasing mechanism.Therefore,the micromanipulation system proved to be effective for active releasing of micromanipulation.A novel gripper structure with triple finger is devised.In the design,three cantilevers are considered as the end effectors of the fingers,driven by piezoelectric ceramic transducer(PZT).Tungsten tipped probes are used to pick and place the micro objects.

Rotation of Biological Cells:Fundamentals and Applications

Cell rotation is one of the most important techniques for cell manipulation in modern bioscience,as it not only permits cell observation from any arbitrary angle,but also simplifies the procedures for analyzing the mechanical properties of cells,characterizing cell physiology,and performing microsurgery.Numerous approaches have been reported for rotating cells in a wide range of academic and industrial applications.Among them,the most popular are micro-robot-based direct contact manipulation and field-based non-contact methods(e.g.,optical,magnetic,electric,acoustic,and hydrodynamic methods).This review first summarizes the fundamental mechanisms,merits,and demerits of these six main groups of approaches,and then discusses their differences and limitations in detail.We aim to bridge the gap between each method and illustrate the development progress,current advances,and prospects in the field of cell rotation.

Melt-spun thin ribbons of shape memory TiNiCu alloy for micromechanical applications

The development of micromechanical devices(MEMS and NEMS)on the basis of nanostructured shape memory alloys is reported.A Ti_(50)Ni_(25)Cu_(25)(at.%)alloy fabricated by the melt spinning technique in the form of a ribbon with a thickness around 40µm and a width about 1.5 mm was chosen as a starting material.Technological parameters were optimized to produce the alloy in an amorphous state.The thickness of the ribbon was reduced to 5–14µm by means of electrochemical polishing.A nanostructural state of the thin ribbons was obtained via the dynamic crystallization of the amorphous alloy by application of a single electric pulse with duration in the range of 300–900µs.A microtweezers prototype with a composite cantilever of 0.8µm thick and 8µm long was developed and produced on the basis of the obtained nanostructured thin ribbons by means of the focused ion beam technique.Controlled deformation of the micromanipulator was achieved by heating using semiconductor laser radiation in a vacuum chamber of scanning ion-probe microscope.

UNDERSTANDING THE MECHANICAL PROPERTIES OF SINGLE MICRO-PARTICLES AND THEIR COMPACTION BEHAVIOUR

The compaction of particulate materials to form tablets is increasingly employed as a final dosage form for functional products due to its simplicity and low cost. However, the functionality of some products may be impaired due to the high compression pressures required. The general aim of the current study is to understand the relationship between the mechanical properties of single feed particles （〈 100μm） and their compaction behaviour in order to produce tablets at low compression pressure with acceptable strength. The materials studied were pharmaceutical excipients, comprising three enteric polymer particles and three different powders in the form of agglomerates. The mechanical properties of the individual particles or agglomerates were determined by a micromanipulation technique. The samples were also compacted in cylindrical tableting dies. It was observed that there was a strong correlation between the forces required to cause the fracture of the single particles and those derived from the compaction measurements as determined using an existing analysis.

Micro Manipulation Using Magnetic Microrobots

When developing microscale robotic systems it is desired that they are capable of performing microscale tasks such as small scale manipulation and transport. In this paper, we demonstrate the transport of microscale objects using single or multiple microrobots in low Reynolds number fluidic environment. The microrobot is composed of a ‘U＇ shaped SU-8 body, coated on one side with nickel. Once the nickel coating is magnetized, the motion of the microrobots can be driven by external magnetic fields. To invoke different responses from two microrobots under a global magnetic field, two batches of microrobots were fabricated with different thicknesses of nickel coating as a way to promote heterogeneity within the microrobot population. The heterogeneity in magnetic content induces different spatial and temporal responses under the same control input, resulting in differences in movement speed. The nickel coated microstructure is manually controlled through a user interface developed using C＋＋. This paper presents a control strategy to navigate the microrobots by controlling the direction and strength of ex- ternally applied magnetic field, as well as orientation of the microrobots based on their polarity. In addition, multiple micro- robots are used to perform transport tasks.

Closed-loop Control Using High Power Hexapole Magnetic Tweezers for 3D Micromanipulation

This paper presents the design,modeling,integration,and application of 3D printed high power hexapole magnetic tweezers for 3D micromanipulation applications.Six sharp-tipped magnetic poles were configured with electromagnetic coils and mounted on 3D printed magnetic yokes to form a tilted Cartesian coordinate system for actuation.A closed loop control algorithm was developed to automatically manipulate external power supplies connected to the magnetic tweezers,by using 3D positional information obtained from real-time image processing techniques.When compared against other designs of magnetic tweezers,our system has a larger working space and can generate higher magnetic field strengths.This allows for more diverse applications regarding small scale manipulation,including cell manipulation and cell therapy.Experiments and analytics explained in this paper demonstrate the closed-loop manipulation of microswimmers can provide a magnetic force as high as 800 pN while maintaining a positional error below 4μm in 3D and 1.6μm in 2D.Using the desired location as the control input,the microswimmers investigated were able to achieve arbitrary 2D and 3D trajectories.We also show that the implemented hexapole magnetic tweezers have adequate power to control microswimmers in Newtonian fluid environments.The system will later be optimized and deployed to control microswimmers in non-Newtonian fluid environments.