Quantitative determination of dimensional properties like length, diameter, height, etc. is essential in research, development and in production process control. To meet these requirements, the widely used approach is the coordinate measurement technique. The equipments - the coordinate measuring machines (CMMs) – using the mentioned technique cover a wide measurement range from meter to nanometer. Below a newly developed equipment for the micro scale is presented. The system – the micro coordinate measuring machines (μCMM) - consists of a probing system, voice coil based actuators and an integrated interferometric measurement system. The key component - in addition to the probing system – is the positioning stage, since the characteristics of the position acquisition and control directly influences the achievable accuracy of the complete measurement system. In contrast to a standard interferometer the presented system utilizes a 2D CMOS image sensor to capture the measurement signal. To drive the stage, a commercial voice coil actuator is used: the scanning range of the introduced system covers about 15 mm, and can be easily extended. The applied probing system uses a ruby ball stylus probe. It is a measuring probe, which means that it provides a signal corresponding to the occurring deflections of the probe ball for all three spatial directions. The probe achieves nanometer resolution.
In this work the improved nanonewton force facility of the Physikalisch-Technische Bundesanstalt (PTB), the German national metrology laboratory, and its possibility of measuring a theoretical predicted negative light pressure between two metallic plates with subwavelength distance is presented. The work includes presentation of upgrades to the existing nanonewton force facility for the realization of the experiment, the measuring methods and the first results obtained with the experimental setup together with comparisons to theoretical calculations.
For numerous applications in science and engineering, the development of technologies for assembling and manipulating macro-, micro-, and nano-objects by means of laser light is of high interest. Most of these attractive forces require dielectric particles they can act on. In recently published papers, a negative light pressure was predicted which acts on metallic bodies if these are separated by a subwavelength slit and which arises from surface plasmon interaction between the metallic bodies1,2. An experimental demonstration of this force has not yet been carried out. First theoretical calculations showed that, for example, a laser power of 100 mW which is fully absorbed in the slit of a laser with a wavelength of 1550 nm would, in a slit having a width of half the wavelength, generate a force of about 1 nN. However, this is roughly three times the force of the radiation pressure of about 0.33 nN.
In this work, we present an experimental setup to measure this force, together with results of refined theoretical calculations and with preliminary results achieved with the experimental setup.
The paper summarize the PTB activities in the field of silicon sensors for dimensional metrology especially roughness measurements and silicon calibration standards developed during the past ten years. A focus lies in the development of 2D silicon microprobes which enable roughness measurements in nozzles as small as 100 μm in diameter. Moreover these microprobes offer the potential for very fast tactile measurements up to 15 mm/s due to their tiny mass and therefore small dynamic forces. When developing high precision tactile sensors care has to be taken, not to scratch the often soft surfaces. Small probing forces and well defined tip radii have to be used to avoid surface destruction. Thus probing force metrology and methods to determine the radius and form of probing tips have been developed. Silicon is the preferred material for the calibration of topography measuring instruments due to its excellent mechanical and thermal stability and due to the fabrication and structuring possibilities of silicon microtechnology. Depth setting standards, probing force setting standards, tip radius and tip form standards, reference springs and soft material testing artefacts will be presented.
This paper presents a micro gripper driven by a new piston type pneumatic micro actuator. The basic structure of the micro gripper and the actuator are fabricated by silicon dry etching in a single etch step. The device consists of a pyrex-silicon-pyrex sandwich structure which was mounted by anodic bonding. Alternatively a SU8 depth lithography process was used to realise the pneumatic driven micro gripper. The assembly of various micro parts including a recently presented tactile silicon 3D-micro probe is described.
Accurate handling of microparts is one of the major tasks for an automated microproduction. The development of centering electrostatic handling devices is described. Based on a planar design common microtechnical fabrication methods were used. Therefore the gripper electrodes can easily be miniaturized and the geometric form can be adapted to the shape of the objects to be handled. The optimization of the design of the gripper was done by using the Finite Element Method. This gave the possibility to improve the centering effect and the gripping forces without increasing the operating voltage. To enable the observation of the gripped parts with a camera, a transparent substrate was used (Pyrex-wafer). This facilitates the integration of the gripper into a sensor controlled microassembly station. Futhermore first successful tests of functional models are described.
A three-axial tactile micro probe for the investigation of the mechanical behavior of micro grippers and other micro assembly equipment has been developed using silicon micromachining technology. The sensor has been used to measure the restoring forces of flexural hinges in a micro gripper gear, to calibrate an integrated gripping force sensor, and to measure the generated forces of actuators used in micro grippers. The tactile micro probe is an advancement of a 3-D force sensor presented earlier.
This paper presents two new designs for a differential-type SMA actuator for a silicon micro gripper. The basic structure of the micro gripper is fabricated by silicon dry etching. The SMA actuators have been realized by machining a NiTi foil with a thickness of 50 ?m. It has been cut by direct laserwriting using a Q-switched Nd:YAG-laser followed by a wet chemical etch step to remove the heat affected zone (HAT). The first design is an advance of a recently presented actuation system with an optimized configuration of the SMA actuator. A critical aspect is the high force necessary to imply the low temperature shape of the inactive actuator which has to be transmitted by the gripper gear. This problem has been overcome by the second design where these high forces are transmitted directly between the active and the inactive actuator of the differential-type actuator. Tests of this new actuator and a new gipper design modified to meet the requirements of the actuator are described.
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