Sam Ogden

A Latchable Valve for High-Pressure Microfluidics

In this paper, the strongest yet latchable valve in subcubic-centimeter size for microfluidic applications is presented. The device has an integrated actuator cavity consisting of three segments filled with paraffin, each operated by a separate heater. At one of the segments, a membrane valve head is deflected by the expansion of the resistively melted paraffin to close against its valve seat. Different heating sequences provide a latched closed or opened valve. The maximum pressure before any leakage occurred was 2.5 MPa. The leak pressure is found to be progressively dependent on the clamping pressure applied. The valve has an opening and closing time of 7 and 1 s, respectively. At an applied pressure of 0.3 MPa, the closed valve needs to be reactivated every 100 min to remain leakage free, leading to an average power consumption of 4.5 mW.

High-Pressure Peristaltic Membrane Micropump With Temperature Control

A high-pressure peristaltic membrane micropump, which is capable of pumping against a back pressure of 150 bar, has been evaluated. The main focus was to maintain the flow characteristics also at high back pressures. The pump was manufactured by fusion bonding of parylene-coated stainless-steel stencils. A large-volume expansion connected to the solid-to-liquid phase transition in paraffin was used to move 10-μm-thick stainless-steel membranes. The pump was evaluated by using two different driving schemes, a four-phase cycle and a six-phase cycle. With the six-phase cycle, a constant flow rate of 0.4 μL min-1 was achieved over an interval ranging from atmospheric pressure to 130 bar. At lower back pressures, the more energy efficient four-phase cycle achieved slightly higher flow rates than the six-phase cycle. However, it required higher driving voltage at high back pressures. Since the pump is thermally activated, a temperature sensor was integrated to control the melting and solidification of paraffin, implying capability of increasing the performance of the pump. With a thickness of only 1 mm as well as a simple and robust design, the micropump is well suited for integration in analytical systems. The high pressures managed are in the region needed for, e.g., high-performance liquid chromatography systems.

High-pressure stainless steel active membrane microvalves

In this work, high-pressure membrane microvalves have been designed, manufactured andevaluated. The valves were able to withstand back-pressures of 200 bar with a response timeof less than 0.6 s. T ...

Microdispenser With Continuous Flow and Selectable Target Volume for Microfluidic High-Pressure Applications

This paper presents a reusable microdispenser intended for continuous flow dispensing of variable and controlled volumes of liquid against high back-pressures. The microdispenser consists of two active valves and a dispenser chamber, all actuated by the volume change associated with the solid-to-liquid phase transition of paraffin wax. It is fabricated using stainless steel sheets, a flexible printed circuit board, and a polyimide membrane. All are covered with Parylene C for insulation and fusion bonding at assembly. A finite element method (FEM) model of the paraffin actuator is used to predict the resulting flow characteristics. The results show dispensing of well-defined volumes of 350 and 540 nL, with a good repeatability between dispensing sequences, as well as reproducibility between devices. In addition, the flow characteristics show no back-pressure dependence of the dispensed flow in the interval 0.5-2.0 MPa. The FEM model can be used to predict the flow characteristics qualitatively.

Miniaturized submersible for exploration of small aqueous environments

Remotely operated vehicles (ROVs) are commonly used for sub-surface exploration. However, multi-functional ROVs tend to be fairly large, while preferred small and compact ROVs suffer from limited functionality. The Deeper Access, Deeper Understanding (DADU) project aims to develop a small submersible concept using miniaturization technologies to enable a high functionality. An operator is able to maneuver the vehicle with five degrees of freedom using eight small thrusters, while a set of accelerometers and gyros monitor the orientation of the submersible. A single fiber optic cable will connect the submersible to a control station and enable simultaneous data and command transfers. Rechargeable battery packs provide power to the submersibles subsystems during operation. These will be rechargeable through the fiber connection. A forward looking camera is aided by a laser topography measurement system, where distances, sizes and shapes of objects in view can be determined to within 0.5 cm. For murkier environments, or when a more extensive mapping of the surroundings is needed, the small high-frequency side-scanning sonar can be used. Salinity calculations of the water will be available through measurements of the conductivity, temperature and depth. Samples of water and particles within it will be enabled through a water sampler with an enriching capability. Flow sensors will be able to measure the water movement around the submersibles hull. The submersible and its subsystems are under continuous development. The vehicle itself, and its subsystems as stand-alone instruments, will enable the exploration of previously unreachable submerged environments, such as the sub-glacial lakes found in Iceland and Antarctica, or other submerged small environments, such as pipe and cave systems.

A latchable high-pressure composite valve actuator combining paraffin and a low melting point alloy

This work presents a latchable valve microactuator for use in high-pressure environments, for instance deep-sea sampling in missions of long duration. Mounted on a minisubmersible, it can be used in confined spaces, earlier virtually unreachable. However, the device can be used in any high-pressure application where long open and/or closed times are required, and power supply is an issue. The actuator is fabricated using standard batch-processes as photochemical machining, wet etching and lithography. Focus of this work is on the endurance of the actuator to facilitate a bistable valve. The actuator managed to keep a deflected position for almost 50 hours at 1.8 MPa applied pressure, after which the experiment was aborted.

Modeling and Analysis of a Phase Change Material Thermohydraulic Membrane Microactuator

Presented in this paper is a finite-element-method-based model for phase change material actuators, modeling the active material as a fluid as opposed to a solid. This enables the model to better conform to localized loads and offering the opportunity to follow material movement in enclosed volumes. Modeling, simulation, and analysis of an electrothermally activated paraffin microactuator have been conducted. The paraffin microactuator used for the analysis in this study exploits the large volumetric expansion of paraffin upon melting, which, combined with its low compressibility in the liquid state, allows for high hydraulic pressures to be generated. The purpose of this study is to supply a geometry-independent model of such a microactuator through the implementation of a fluid model rather than a solid one, which has been utilized in previous studies. Numerical simulations are conducted at different frequencies of the heating source and for different geometries of the microactuator. The results are compared with the empirical data obtained on a close to identical paraffin microactuator, which clearly show the advantages of a fluid model instead of a solid-state approximation.

Body Surface Backed Flexible Antennas for 17 GHz Wireless Body Area Networks Sensor Applications

Body surface backed single and multiple notch antennas for 17 GHz on body wireless sensor communications are presented in this paper. The proposed antennas are designed to excite both body surface wave propagations and off body radiations, which are strictly required by wireless body area networks (WBAN) sensor communications. To realize those propagations and radiations, human body surface is utilized as a reflector for the antennas. The presented antennas fabricated on 100 um thick polyimide flexible laminates are numerically and experimentally studied both in free space and on real body surface, and the body effects on antenna impedance and radiation performance are also analyzed. Good agreements between simulations and measurements are achieved. It is shown that the proposed antennas feature about 10% impedance bandwidth (S11 = -10 dB) and higher than 3.7 dBi gain in free space. The antenna resonant frequencies are slightly detuned and the antenna gain is increased when they are placed close to body surface. Moreover, the surface wave propagations and radiations off body surface are also investigated by measuring transmissions between two identical single and multiple notch antennas on body surface, respectively.

A latchable paraffin actuated high-pressure microfluidic valve

In this paper, the strongest yet latchable valve in sub-cm3 size for microfluidic applications is presented. The device has an integrated actuator cavity consisting of three segments filled with paraffin and operated by separate heaters. At one of the segments, a membrane valve head is deflected from the expansion of the resistively melted paraffin to close against its valve seat. Different heating sequences provide a latched closed or opened valve. The maximum pressure before any leakage occurred was 1.3 MPa. At higher pressures the leakage increases until the valve is fully open at 2.3 MPa. The valve has an opening and closing time of 9 and 1 s, respectively. At an applied pressure of 0.3 MPa, the closed valve needs to be reactivated every 100 min to remain leakage free, leading to an average power consumption of 4 mW.