The present invention relates to a fluid pump for pumping a fluid from an inlet to an outlet. The present invention further relates to a method for operating such a fluid pump. The fluid pump includes a pump body (10) having at least a first opening (13) and a second opening (14), a deflectable pump diaphragm (11) attached to the pump body (10) is mounted such that a pump chamber (12) between the the pump body (10) and the membrane (11) is formed and in that said pump chamber (12) via the first opening (13) with an inlet and via the second opening (14) having an outlet in fluid communication, and a valve seat (15 ) projecting (in the interior of the pump chamber 12) about the second opening (14) is arranged around, and in the undeformed height of the second opening (14) into the pump chamber (12) (to the pump membrane 11) such that the deflectable membrane (11) corresponding to close and open a fluid passage through the outlet in contact with the valve seat (15) and is operable by moving away thereof. The valve seat (15) has an elastic body (16) and a seal (17) with a sealing surface.

This article presents a non-destructive test procedure for bond strength characterization. The approach is based on a modified blister test where the length of an artificially generated crack in combination with the applied pressure indicates the bond strength of the composite. For geometry determination, different test structures were analyzed. Thereby, the pressure independent ratio between volume displacement and newly generated crack area during proceeding crack propagation is the determining factor for a non-destructive test character.

We present - for the first time - a novel design of a micropump which enables a backpressure-independent flow rate up to 20 kPa within the low flow regime required for drug delivery systems. Our concept, based on two piezoelectrically actuated diaphragms, allows an accurate dosing in the range of 1 - 50 µ l/min with freely programmable release profiles and offers the potential to minimize chip size and power consumption in comparison to 3-actuator peristaltic micropumps. The stroke volume is adjustable between 50 - 200 nl by means of voltage control which enables a high resolution volumetric dosing. Within the relevant frequency range below 2 Hz the flow rate is proportional to the frequency. Our design also excels in its comparably simple and robust 2-layer fabrication process.

This paper presents a novel test method for a non-destructive strength characterization of bonded silicon wafer pairs. The test is based on a controlled crack generation at the bond interface using a modified blister test method. An analytical model was used to establish an essential design parameter. Therewith, different test structures were analyzed and important information about crack generation and crack propagation were gained. Finally, the theory of controlled crack generation was verified and demonstrated by a modified blister test.

We present a fully analytical model for micro-diaphragm pumps with active valves, based on the peristaltic working principle. Our model is suited for very fast as well as for very slow actuation mechanisms. Therefore it can be applied to a variety of actuation principles, e.g. piezoelectric, pneumatic, thermo-pneumatic or pre-stressed shape memory actuation. We show that the dynamics of this kind of micropump can be fully described by a lumped element approach taking only the mechanical behaviour of the diaphragms and the viscous losses at the valves into account. The full flow versus frequency and backpressure characteristic is derived. Our model is capable of predicting the maximum achievable flow rate and the maximum sustainable backpressure of micro-diaphragm pumps with active valves. Different modes of operation, which are distinguished by the speed of the actuation mechanism, the pressure history inside the pump and the applied driving scheme, are identified. We show that micro-diaphragm pumps with active valves generally suffer from a linear dependence of the flow rate on the applied backpressure. This fact, which is already known from micropumps with passive valves, is remarkable, because it is in contradiction to the characteristics of macroscopic peristaltic pumps. A set of design rules for the dimensioning of the valves in dependence on the actuation force and the desired hydrodynamic characteristics (maximum flow rate and maximum sustainable backpressure) are derived. Our theoretical results are proven by experimental results of our piezoelectrically actuated micropump. A maximum flow rate of 1.4 ml min−1 and a maximum sustainable backpressure of 40 kPa were achieved.

No highly integrated sphincter prosthesis for therapy of anal incontinence exists. Therefore, this trial was performed to develope a novel artificial sphincter: the German Artificial Sphincter System „GASS“. This device combine the fluid reservoir, the occlusion cuff and micropump to a highly integrated device. The GASS is completely manufactured of polyurethane. The micropump is based on piezo-technology. Threshold of continence and the pressure-volume relationship of the cuff prosthesis were evaluated in an in vitro simulator using isolated porcine bowel segments and isolated anal canals. Minimal filling volumes between 6.5 and 7 cc could maintain continence for liquids against high luminal pressures. The high pressure zone of the occlusion cuffs reached only intraluminal pressure values between 36-76 mm Hg, indicating a little risk of ischaemie injury of the bowel respectively the anal canal. In summery, an integrated, patented and functionable sphincter device, easy to implant, could be realized.

No highly integrated sphincter prosthesis for therapy of major fecal incontinence exists. Therefore, we developed a novel neosphincter, made of polyurethane. The GASS consists of a support ring (SR) which includes a fluid reservoir, fixed on the outer diameter of the SR, and a multi-chamber occluding cuff (C-int) on the inside diameter. The total inflation volume of C-int is about 23 cc. The integrated micropump based on piezotechnology measures 30x13x1 mm(3) (flowrate 1.4 cc/min, max. backpressure 40000 Pa). GASS was evaluated around the external sphincter of isolated porcine anal canals. The threshold of continence was defined as the inflating volume wich water ceased to leak through the area occluded by C-int under an induced rectal pressure of 150 cm H2O. Minimal filling volumes maintained continence for liquids against high luminal pressures. A low intraanal resting pressure (Deltap(anal)) induced by activated GASS indicates a little risk of ischemic injury of the anal canal in vivo (median Deltap(anal) 24.1 mm hg:15cc vs 46.9 mm hg:21cc). In summary, a highly integrated and efficient high-tech neosphincter for the therapy of major fecal incontinence could be realized.

This paper deals with the formation and breakdown of liquid jets from different nozzle designs with square cross section. The jet formation is quantitatively examined in terms of a scaled viscosity and pressure transient for a convergent nozzle design. The study also shows, that a divergent nozzle outlet should be avoided, because it may cause asymmetric disturbances on the jet. Two different mechanisms of jet breakdown occur in dependence on the nozzle geometry. Curves of the critical Weber number vs. Reynolds number are calculated.

Any microfluidic device depends on a proper and complete filling with liquid. In many cases entrapped air bubbles will drastically alter device performance and thus have to be avoided. Especially the dosing of liquids with micropumps or free jet dispensers is heavily influenced by the existence of gas bubbles. Also optical detection in microfluidic systems may fail due to light reflection at entrapped gas bubbles. In consequence a reliable liquid filling is a key design issue in microfluidics.Although the importance of this attribute is commonly accepted there is no established set of design rules for the geometry of "filling-friendly" microfluidic structures. We have therefore examined the filling of fluidic reservoirs and channels with arbitrary cross-sections to provide design rules for self-priming.

This paper describes process development, fabrication and testing of piezoelectric micro actuators based on a novel polymer-composite technology. Fabrication is done by using segmented silicone molds for the insert-casting of piezoactuators into polymeric material. Furthermore, a simulation model was developed to forecast the principal behavior of the micro actuators and to perform an optimization of the stroke. Based on these results, a number of test structures were fabricated. Finally the displacement was measured and compared to the simulation model.

The main disturbances occuring with gravimetrical measurements of small quantities of liquid are investigated in detail. To reduce evaporation, an evaporation trap can be used. If such a trap is used, the condensation and the humidity distribution in the trap has to be taken into account too. If a tubing is placed between the microfluid device and the liquid in the receptacle additional disturbances occures. The amount of liquid mass pulled from the tubing by surface tension is more than four orders of magnitudes larger than the resolution of up to date balances. Therefore, fluctuations caused by the tubing roughness are a significant measurement effect that cannot be neglected. This was verified by a theoretical model and by experiments. To reduce these effects the roughness of the tubing and the surface tension of the liquid has to be minimized.

We present a fabrication technique for single electron tunnel junctions in silicon. Based on Bonded and Etched back Silicon On Insulator (BESOI) material with a very thin silicon top layer tunnel junctions are realized by electron beam lithography (EBL) in combination with a two-layer resist system. The pattern is transferred by anisotropic reactive ion etching (RIE), The lateral dimensions are reduced further by thermal oxidation in a subsequent step, The process technology is, apart from the e-beam lithography, fully MOS compatible,Different samples with four tunnel junctions in series were characterized at 6 K. The I/U-characteristics reveals a Coulomb blockade as well as a Coulomb staircase, which can be attributed to the asymmetrical structure. By realizing a backgate configuration periodic modulations in the source drain current versus the gate voltage have been measured.