Dominiek Reynaerts

Assembly of microsystems

In the microworld, as well as in the macroworld, assembly is a crucial operation in the genesis of a product. This keynote paper focusses on the assembly problems occurring in the manufacturing cycle of microsystems. Scaling effects make that the assembly problems are different in the microworld. The different assembly operations and techniques, like manipulation by physical contact, non-contact manipulation, smart assembly techniques, and joining methods are thoroughly discussed. Finally, some relevant examples of micro-assembly systems and of assembled microproducts are given.

The MANUS-HAND Dextrous Robotics Upper Limb Prosthesis: Mechanical and Manipulation Aspects

Dextrous artificial hand design and manipulation is an active research topic. A very interesting practical application is the field of upper limb prosthetics. This paper presents the mechanical design and manipulation aspects of the MANUS-HAND project to develop a multifunctional upper limb prosthesis. The kinematics of our design makes use of the so-called underactuated principle and leads to an innovative design that triples the performance of currently existing commercial hand prosthesis. In addition, the thumb design allows its positioning both in flexion and opposition. As a consequence, up to four grasping modes (cylindrical, precision, hook and lateral) are available with just two actuators.The proposed impedance control approach allows the fingers to behave as virtual springs. Given the difficulty of including the user in the control loop, this approach is based on an autonomous coordination and control of the grasp. As a consequence, the requirements on the Human Machine interface are reduced. At the end of the paper, we briefly describe the clinical trials that were set up for evaluation purposes.

Pneumatic and hydraulic microactuators: A review

The development of MEMS actuators is rapidly evolving and continuously new progress in terms of efficiency, power and force output is reported. Pneumatic and hydraulic are an interesting class of microactuators that are easily overlooked. Despite the 20 years of research, and hundreds of publications on this topic, these actuators are only popular in microfluidic systems. In other MEMS applications, pneumatic and hydraulic actuators are rare in comparison with electrostatic, thermal or piezo-electric actuators. However, several studies have shown that hydraulic and pneumatic actuators deliver among the highest force and power densities at microscale. It is believed that this asset is particularly important in modern industrial and medical microsystems, and therefore, pneumatic and hydraulic actuators could start playing an increasingly important role. This paper shows an in-depth overview of the developments in this field ranging from the classic inflatable membrane actuators to more complex piston–cylinder and drag-based microdevices.

Design aspects of shape memory actuators

Abstract The need for high performance and at the same time compact actuators has existed for a long time, especially for multi-degree-of-freedom devices like robot hands and walking robots. These devices mostly use electrical actuators. Also for the presented research, the interest in designing actuators based on shape Memory Alloys emerged from a study in the field of multi-fingered robot hands. Shape Memory Alloy actuation is very attractive because of the very high power density that can be obtained using these materials. When calculating the ratio of actuator output to actuator volume, also called power density, SMA actuators offer even higher values than hydraulic actuation. Nevertheless, controlling these actuators and implementing them in robotic systems is not so straightforward. This paper defines a number of design rules for shape memory alloy based robotic actuators. It is demonstrated that SMA actuation offers very attractive properties for example in space applications and especially in a zero-gravity environment. This paper also shows that, when using an appropriate cooling method, accurate position control for Shape Memory Alloy actuators can be obtained.

An implantable drug-delivery system based on shape memory alloy micro-actuation

Abstract Shape memory alloy actuators feature an extremely high power-to-volume ratio. This property is a major advantage for miniature applications. This paper describes implantable drug-delivery systems based on shape memory alloy micro-actuation. A first type is designed for use with solid drugs while a second design enables delivery of liquid drugs. The operating principle of the latter system is based on a precisely controlled discontinuous release from a pressurized reservoir. It is realized using a shape memory actuated microwave system. One dose can be controlled with an accuracy up to 5 μl. The system is remotely powered and controlled using a transcutaneous transformer. A refilling possibility based on transcutaneous injections is provided. The design of the valve is such that it can be mounted on a printed circuit board together with the other electrical components. Furthermore, the valve is optimized towards aspects like biocompatibility, low-cost production, lifetime, safety and minimal dimensions. The drug-delivery system is aiming at patients who need multiple injections each day over a long period of time. The current prototype could already reduce the number of injections by a factor of 200. By further miniaturization a reduction factor of 3000 could be obtained.

Design of miniature parallel manipulators for integration in a self-propelling endoscope

Abstract This paper presents two designs for a miniature robotic manipulator that has to be integrated into a self-propelling endoscope. The endoscope is meant to inspect and intervene in the human colon through which it moves by inchworm locomotion. Both manipulator designs are based on a 3-degree-of-freedom (dof) Stewart platform, either driven by hydraulic pistons or by electromagnetic motors. The hydraulic manipulator is 12 mm in diameter and 30 mm long. It has a stroke of 10 mm and tilts 30–35°. The system is designed to be used at pressures up to 10 bar at which each piston generates a force of 7 N. Piezoelectric and electromagnetic valves are developed that will be integrated into the manipulator. The electrical platform has three telescopic legs driven by a motor-spindle combination. This manipulator has a length and diameter of respectively 50 and 15 mm, and generates speeds up to 5 mm/s and forces up to 1.2 N per leg.

Development of an axial microturbine for a portable gas turbine generator

A miniature gas turbine is under development with the aim of generating electrical energy from fuel. This system consists of a compressor, combustion chamber, turbine and generator. The turbine is a single-stage axial impulse turbine (Laval turbine) with a rotor diameter of 10 mm, made of stainless steel using die-sinking electro-discharge machining. It has been tested with compressed air to speeds up to 160 000 rpm and generates a maximum mechanical power of 28 W with an efficiency of 18.4%. When coupled to a small generator, it generates 16 W of electrical power, which corresponds to an efficiency for the total system of 10.5%. The power density is mainly limited by the maximal speed of the ball bearings. The main losses are the blade profile losses and the exit losses. Higher speeds can considerably reduce the exit losses and therefore increase efficiency and power density. An improved turbine has been tested at temperatures up to 360 °C and generates up to 44 W of electrical energy with a total efficiency of 16%. A 20 mm diameter centrifugal compressor matching the pressure and flow characteristics of the turbine has been designed and is currently under construction.

Microstructuring of silicon by electro-discharge machining (EDM) — part I: theory

Abstract Currently, nearly all microcomponents are fabricated by micro-electronic production technologies like etching, deposition and other (photo) lithographic techniques. In this way, main emphasis has been put on surface micromechanics. The major challenge for the future will be the development of real three-dimensional microstructures. The main objective of the proposed research is the development of a production technology for three-dimensional micromechanical structures together with a study of the mechanical properties of these structures. Electrodischarge machining (EDM) is a versatile technique which is very well suited for machining complex microstructures. This paper starts with an overview of EDM technology, the current state-of-the-art of micro EDM, and a comparison of EDM with other micromachining technologies. Afterwards, the basic parameters for EDM of silicon are derived. It will be demonstrated that EDM of silicon is not only feasible, but also forms an interesting, powerful and complementary alternative to traditional silicon micromachining.

Design of an advanced tool guiding system for robotic surgery

This paper describes an advanced tool guiding system for robot assisted surgery. It is offering two additional local degrees of freedom to a standard robotic tool guiding system like of the Zeus robotic surgery system. The tool guide is basically a tube that guides the inserted surgical instrument to the desired location. By adding two bending degrees of freedom at the tip, the developed system largely increases the maneuverability of the instrument. It consists of a micromachined superelastic tube driven by a conventional cable system. Main issue was the design of a flexible hinge system in superelastic NiTi that offers the desired bending angles (at least 90 degrees in both directions) and that is compatible with the material limits for long-time cycling. Based on extended FE calculations and experimental measurements the second-generation design offers 90 degrees bending in both directions. The improvement over previous devices is the combination of two degrees of freedom with a small diameter of only 5 mm. An additional advantage is the tool channel, which enables the use of different instruments with this single device.

Design of a ring-shaped three-axis micro force/torque sensor

Abstract This paper describes the design of a piezoresistive, three-axis, hollow micro force/torque sensor. This sensor will be mounted in the Smartpen™, developed and commercialized by SmartPen N.V. Considering the products geometrical restrictions, the sensor dimensions are: maximum outer diameter 12 mm; total length 20 mm; minimum inner diameter 7.5 mm. As an additional constraint, the sensor has to be low cost and is to be manufactured in large quantities in an automated production environment. This paper states the role of the force/torque sensor in the Smartpen™. A method to derive nominal and maximal sensor loading is explained. First, a rough design based on a known sensor concept and calculated using a parametric two-dimensional finite-element model is presented. To calculate detailed characteristics of the sensor, a three-dimensional finite-element model of the sensor is presented. In order to validate the theoretical models used, some preliminary experimental results are also presented.