Werner Karl Schomburg

Fabrication of Molded Interconnection Devices by Ultrasonic Hot Embossing on Thin Polymer Films

Ultrasonic hot embossing allows fabrication of metal patterns onto a polymer film with a low cost and rapid process. A polymer layer with a thin metal film on top is welded onto the polymer substrate where there are protruding micro structures on the tool. Edges around the protruding structures cut the metal layer and ensure electrical insulation. The entire process performs in a few seconds. The non-welded areas are mechanically removed after this process. An antenna of a radio frequency identification device (RFID) and a flexible membrane keyboard were fabricated by embossing 10- mum-thick conductive paths from an aluminum foil onto polypropylene films, 150 and 250 mum in thickness. Antenna circuits have been proven to show the expected resonance frequencies and the keyboard was successfully employed as an input device for a PC.

Introduction to microsystem design

Preface.- Notations and symbols.- Introduction.- Scaling Laws.- Elastic deformations.- Thin Films.- Conductor Paths.- Membranes.- Strain gauges on membranes.- Beams.- Vibrations.- Capillaries.- Capacitive forces.- Piezoelectric effect.- Thermal actuators.- Micro optics.- Diffusion.- Micro valves.- Micro pumps.- Micro dosing.- Analogies between physical domains.- Mechanical devices for electronics.- Pressure sensors.- Flow sensors.- Inertial sensors.

Polymer micro piezo valve with a small dead volume

A polymer valve with a small dead volume in the range of 6 nl and a response time faster than 1 ms is presented. The valve structure is simple and therefore easy to fabricate by injection molding or hot embossing. A layer of silicone rubber applied by a stamping technique not only promotes the sealing of the valve but also defines the gluing area during assembly. The fabrication is based on the AMANDA-process, which allows low-cost batch production of polymer micro devices.

Review on ultrasonic fabrication of polymer micro devices

Fabrication of micro devices from thermoplastic polymers by ultrasonic processing has become a promising new technology in recent years. Microstructures are generated on polymer surfaces with cycle times of a few seconds and are tightly sealed in even shorter times. Investment costs and energy consumption are comparatively low and processes are very flexible enabling economic fabrication even for small-scale production. For large-scale production role-to-role fabrication has been shown reducing costs even more. A variety of micro devices have been introduced up to now mostly for microfluidic applications. Besides this, electronic circuit boards are fabricated by ultrasonic processing.

Ultrasonic Hot Embossing

Ultrasonic hot embossing is a new process for fast and low-cost production of micro systems from polymer. Investment costs are on the order of 20.000 € and cycle times are a few seconds. Microstructures are fabricated on polymer foils and can be combined to three-dimensional systems by ultrasonic welding.

The design of metal strain gauges on diaphragms

Metal strain gauges need to be designed differently from strain gauges made from silicon. In this paper equations are derived that allow us to calculate the resistance change of metal strain gauges as a function of the position on a thick diaphragm, a thin membrane and a disc simply supported at the rim. The results of finite element calculations presented reveal that large deviations from these equations occur for strain gauges on thin membranes made of soft materials.

A thermopneumatically actuated bistable microvalve

A bistable polymer microvalve with a thermopneumatic actuator has been developed. The microvalve was fabricated by micro milling of a polymer combined with sputtering and photolithography. The valve comprises two 2/2-way valves which are alternately switched such that they can be connected to serve as a 3/2-way valve. Two permanent magnets work with a movable soft magnet to keep the valve in its current state, resulting in bistable switching with a minimum energy of 320 mJ. An air flow rate of 1.36 L min−1 is achieved at 20 °C with a pressure difference of 200 kPa. No leakage is observed up to a differential pressure of 350 kPa. Flowing and switching performances were also tested at different temperatures. Sealing the flow channels from the actuator chamber makes the valve less sensitive to the temperature and other properties of the fluid to be switched. An initial gap between the valve seat and the silicone sealing membrane at least reduces the sticking problem. Switching time is found to be significantly influenced by the thickness of the heating membrane. With an 8 µm thick heating membrane, a response time of 10 ms can be achieved.

Respiration activity monitoring system for any individual well of a 48-well microtiter plate

BackgroundSmall-scale micro-bioreactors have become the cultivation vessel of choice during the first steps of bioprocess development. They combine high cultivation throughput with enhanced cost efficiency per cultivation. To gain the most possible information in the early phases of process development, online monitoring of important process parameters is highly advantageous. One of these important process parameters is the oxygen transfer rate (OTR). Measurement of the OTR, however, is only available for small-scale fermentations in shake flasks via the established RAMOS technology until now. A microtiter plate-based (MTP) μRAMOS device would enable significantly increased cultivation throughput and reduced resource consumption. Still, the requirements of miniaturization for valve and sensor solutions have prevented this transfer so far. This study reports the successful transfer of the established RAMOS technology from shake flasks to 48-well microtiter plates. The introduced μRAMOS device was validated by means of one bacterial, one plant cell suspension culture and two yeast cultures.ResultsA technical solution for the required miniaturized valve and sensor implementation for an MTP-based μRAMOS device is presented. A microfluidic cover contains in total 96 pneumatic valves and 48 optical fibers, providing two valves and one optical fiber for each well. To reduce costs, an optical multiplexer for eight oxygen measuring instruments and 48 optical fibers is introduced. This configuration still provides a reasonable number of measurements per time and well. The well-to-well deviation is investigated by 48 identical Escherichia coli cultivations showing standard deviations comparable to those of the shake flask RAMOS system. The yeast Hansenula polymorpha and parsley suspension culture were also investigated.ConclusionsThe introduced MTP-based μRAMOS device enables a sound and well resolved OTR monitoring for fast- and slow-growing organisms. It offers a quality similar to standard RAMOS in OTR determination combined with an easier handling. The experimental throughput is increased 6-fold and the media consumption per cultivation is decreased roughly 12.5-fold compared to the established eight shake flask RAMOS device.

Coded ultrasonic remote control without batteries

A concept for battery-less remote controls has been developed based on mechanically actuated beams and micro whistles generating ultrasound signals. These signals need to be frequency or time coded to increase the number of signals which can be distinguished from each other and environmental ultrasound. Several designs for generating coded ultrasonic signals have been investigated.

Metal strain gauges on membranes at large deflection

The output signal of metal strain gauges on membranes combined into a half bridge was investigated at deflections larger than three times their thickness. It was discovered that the signal reaches a maximum and then decreases with increasing deflection. When the pressure was applied in the opposite direction, the signal went through a minimum and then rose with increasing deflection. This can be interpreted as a shape transition of the membrane when deflected by more than its thickness. Besides this, the asymmetry of the signal with respect to drops in pressure in opposite directions of the membrane indicates that straining of the neutral fiber of the membrane shows a notable effect. The bridge output was also investigated with strain gauges on bi-stable membranes buckling due to compressive residual stress either up or down when no pressure difference was applied.