Johan Coosemans

Production and characterization of a hydraulic microactuator

In order to improve the power density of microactuators, recent research focuses on the applicability of fluidic actuation at the microscale. The main encountered difficulties in the development of small fluidic actuators are related to production tolerances and assembly requirements. In addition, these actuators tend to comprise highly three-dimensional parts, which are incompatible with traditional microproduction technologies. This paper presents accurate production and novel assembly techniques for the development of a hydraulic microactuator. Some of the presented techniques are widespread in precision mechanics, but have not yet been introduced in micromechanics. A prototype hydraulic microactuator with a bore of 1 mm and a length of 13 mm has been fabricated and tested. Measurements showed that this actuator is able to generate a force density of more than 0.23 N mm(-2) and a work density of 0.18 mJ mm(-3) at a driving pressure of 550 kPa, which is remarkable considering the small dimensions of the actuator.

Integrating wireless ECG monitoring in textiles

This paper reports for the first time on the realization of a garment embedded patient monitoring system, including wireless communication and inductive powering. The developed system is primarily intended for the continuous monitoring of the electrocardiogram (ECG) of children with an increased risk of SIDS (sudden infant death syndrome). The sensors and the antenna are made out of textile materials. All electronics are mounted on a flexible circuit to facilitate integration in the babys pyjamas. A significant increase in the comfort of patient and nursing staff is achieved by this integration in textiles. A prototype baby suit was fabricated and successfully tested by a 21 weeks old baby.

A fluidic micro-actuator with an integrated inductive position sensor

An important technological barrier in the development of microrobotic systems is the lack of compact sensor-actuator systems. This paper presents a piston-cylinder fluidic microactuator with an integrated inductive position sensor. Such positioning systems offer great opportunities for all devices that need to control a large number of degrees of freedom in a restricted volume. The main advantage of fluidic actuators is their high force and power density at microscale. The outside diameter of the actuator developed in this research is 1.3 mm and the length is 15 mm. The stroke is 12 mm, and the actuation force is more than 0.4 N at a supply pressure of 550 kPa. The position sensor consists of two coils wound around the cylinder of the actuator. The measurement principle is based on the change in coupling factor between the coils as the piston moves in the actuator. The sensor is extremely small since one layer of 25 μm copper wire is sufficient to achieve an accuracy of 10 μm over the total stroke. Measurements showed that the actuator achieves a positioning accuracy of 20 μm in closed loop control.

Comparison of two seal technologies for hydraulic microactuators

In order to improve the power density of microactuators, recent research focuses on the applicability of fluidic power at microscale. One of the reasons that hydraulic actuators are still uncommon in micro system technology is due to the difficulty of fabricating powerful microseals. This paper presents two seal technologies that are suitable for sealing small-scale hydraulic actuators. Measurements on prototype actuators show that force densities up to 0.45 N/mm/sup 2/ (0.025 N/mm/sup 3/) and work densities up to 0.2 mJ/mm/sup 3/ can easily be achieved with the developed seal technology. These characteristics can still be improved as the maximum driving pressures of the actuators have not yet been determined.

Evolution in Bladder Pressure Measuring Implants Developed at K.U.Leuven

Bladder pressure monitoring devices have been a topic of great interest for the past two decades. Three devices developed at ESAT-MICAS in this time are reviewed, showing the evolution of these devices. Two of these devices are diagnostic tools small enough to be inserted into the bladder cavity through minimal invasive cystoscopy. The third device is a long term bladder pressure monitoring implant that, if used to drive an artificial sphincter muscle, forms a urological pacemaker that could diminish or rule out urinary incontinence. After a summary of the three devices, recent results are presented from one of the diagnostic tools.