Waterproof sensor system for simultaneous pressure and hot-film flow measurements

For simultaneous measurement of pressure and near surface flow conditions allowing indirect determination of wall shear stress in experimental water tunnel environment an integrated hybrid sensor system has been developed. In contrast to known approaches, which are limited to the use in gas atmosphere due to protruding electrical and fragile parts, our sensor system is waterproof shielded and embedded in epoxy resin. Furthermore an amplification circuit for the pressure signal based on a programmable gain amplifier is integrated in direct vicinity to the pressure sensor in order to minimize noise by electromagnetic disturbances. Also sensor systems with on-board digitalization of the pressure signal for direct digital read-out were realized. We present all aspects of system assembly and embedding to one waterproof module. Furthermore, read-out strategies as well as sensor test results in air and water are shown and watertightness is confirmed

Microgrippers to handle Organoids and pancreatic Islets for Precision Measurements of biological Function

The model of the cultured single cell is considered insufficient to explain the physiological regulation taking place at the organ level. The same is true for the prediction of drug action at the organ level or at the level of the intact organism. For these reasons 3D cell culture models are in increasing demand. It is thus necessary to develop the instruments to handle such cell aggregates and organoids in a controlled, precise and gentle manner. Here, a microgripper is presented which is able to work in aqueous solutions and which is compatible with electrophysiological recordings of the cells immobilized by it. It was successfully employed to position isolated pancreatic islets and a 3D cell culture model of insulin-secreting cells, the so-called MIN6-pseudoislet. As required it was possible to measure the membrane potential of cells within these aggregates without any interference from the microgripper

A Disposable Pneumatic Microgripper for Cell Manipulation with Image-Based Force Sensing

A new design for a single-use disposable pneumatic microgripper is presented in this paper. It enables very cost-eective batch microfabrication in SU-8 with a single lithography mask by shifting manufacturing complexity into reusable components. An optically readable force sensor with potential to be used in a feedback loop has been integrated in order to enable gripping with a controlled force. The sensors are first examined separately from the gripper and exhibit good linearity. The gripper function utilizes the disposable gripper element together with a reusable gripper fixture. During experiments, the pneumatically actuated microgripper can vary the gripping force within a range of a few mN (up to 5.7 mN was observed). This microgripper is planned to be used in a liquid environment for gripping larger aggregates of cells in combination with the patch clamp technique. This approach will allow Langerhans islets suspended in an electrolyte solution to be grasped and held during electrophysiological measurements without cell damage

Structural integrated sensor and actuator systems for active flow control

An adaptive flow separation control system is designed and implemented as an essential part of a novel high-lift device for future aircraft. The system consists of MEMS pressure sensors to determine the flow conditions and adaptive lips to regulate the mass flow and the velocity of a wall near stream over the internally blown Coanda flap. By the oscillating lip the mass flow in the blowing slot changes dynamically, consequently the momentum exchange of the boundary layer over a high lift flap required mass flow can be reduced. These new compact and highly integrated systems provide a realtime monitoring and manipulation of the flow conditions. In this context the integration of pressure sensors into flow sensing airfoils of composite material is investigated. Mechanical and electrical properties of the integrated sensors are investigated under mechanical loads during tensile tests. The sensors contain a reference pressure chamber isolated to the ambient by a deformable membrane with integrated piezoresistors connected as a Wheatstone bridge, which outputs voltage signals depending on the ambient pressure. The composite material in which the sensors are embedded consists of 22 individual layers of unidirectional glass fiber reinforced plastic (GFRP) prepreg. The results of the experiments are used for adapting the design of the sensors and the layout of the laminate to ensure an optimized flux of force in highly loaded structures primarily for future aeronautical applications. It can be shown that the pressure sensor withstands the embedding process into fiber composites with full functional capability and predictable behavior under stress

Micro-Grippers with Femtosecond-Laser Machined In-Plane Agonist-Antagonist SMA Actuators Integrated on Wafer-Level by Galvanic Riveting

In-plane shape memory alloy (SMA) actuators operated in agonist-antagonist mode are integrated on silicon micro-grippers. The actuator elements are cut out of sheet material in a femtosecond laser ablation process. The assembly process is carried out on wafer-level, and the fixation realized by galvanic riveting. The initial deformation of the differential actuators needed to access their actuation potential is implemented during the gripper connection to energy supply

An Immersible Microgripper for Pancreatic Islet and Organoid Research

To improve the predictive value of in vitro experimentation, the use of 3D cell culture models, or organoids, is becoming increasingly popular. However, the current equipment of life science laboratories has been developed to deal with cell monolayers or cell suspensions. To handle 3D cell aggregates and organoids in a well-controlled manner, without causing structural damage or disturbing the function of interest, new instrumentation is needed. In particular, the precise and stable positioning in a cell bath with flow rates sufficient to characterize the kinetic responses to physiological or pharmacological stimuli can be a demanding task. Here, we present data that demonstrate that microgrippers are well suited to this task. The current version is able to work in aqueous solutions and was shown to position isolated pancreatic islets and 3D aggregates of insulin-secreting MIN6-cells. A stable hold required a gripping force of less than 30 μN and did not affect the cellular integrity. It was maintained even with high flow rates of the bath perfusion, and it was precise enough to permit the simultaneous microfluorimetric measurements and membrane potential measurements of the single cells within the islet through the use of patch-clamp electrodes

MEMS Pressure Sensors Embedded into Fiber Composite Airfoils

The paper describes the integration of pressure sensors into fiber composite in order to obtain flow sensing airfoils to be used in future aircrafts. First, the sensor design and working principle is described, followed by an embedding procedure for damage-free integration. Here the sensors are faced to stresses by vacuum and curing during the embedding process into fiber-reinforced plastic. The mechanical characteristics and the influence of external mechanical stresses on the integrated sensor are further investigated. Finally, a sensor design unsusceptible to external mechanical stresses parallel to the surface of the airfoil is proposed and verified by tensile stress tests

Sensor and Actuator Systems for Active Flow Control

An adaptive flow separation control is designed and implemented as it is an essential part of the high lift airfoil designed in B1. The state of the flow is measured nonintrusively using pressure and hot-film sensors implemented on the top side of the airfoil. To avoid flow separation on the Coanda flap a closed loop controlled system is realized using a pressurized mass flow m added to the flow on the Coanda flap. The essential designs of the sensors and actuators are described in [1]. The following article reports on the fabrication and implementation of the combined actuator and sensor system. This includes the fabrication methods, the assembling and tests prior to theirs usage on the high lift airfoil. Hereby a key aspect is the water resistance of the assemblies since they are designed to be used in a water tunnel environment. Furthermore this condition has a high impact on the physical behavior of both the sensors and actuators, which is quantified in additional tests

Robust Pressure Sensor in SOI Technology with Butterfly Wiring for Airfoil Integration

Current research in the field of aviation considers actively controlled high-lift structures for future civil airplanes. Therefore, pressure data must be acquired from the airfoil surface without influencing the flow due to sensor application. For experiments in the wind and water tunnel, as well as for the actual application, the requirements for the quality of the airfoil surface are demanding. Consequently, a new class of sensors is required, which can be flush-integrated into the airfoil surface, may be used under wet conditions-even under water-and should withstand the harsh environment of a high-lift scenario. A new miniature silicon on insulator (SOI)-based MEMS pressure sensor, which allows integration into airfoils in a flip-chip configuration, is presented. An internal, highly doped silicon wiring with "butterfly" geometry combined with through glass via (TGV) technology enables a watertight and application-suitable chip-scale-package (CSP). The chips were produced by reliable batch microfabrication including femtosecond laser processes at the wafer-level. Sensor characterization demonstrates a high resolution of 38 mVV-1 bar-1. The stepless ultra-smooth and electrically passivated sensor surface can be coated with thin surface protection layers to further enhance robustness against harsh environments. Accordingly, protective coatings of amorphous hydrogenated silicon nitride (a-SiN:H) and amorphous hydrogenated silicon carbide (a-SiC:H) were investigated in experiments simulating environments with high-velocity impacting particles. Topographic damage quantification demonstrates the superior robustness of a-SiC:H coatings and validates their applicability to future sensors