Abstract:
The force transducer includes a composite spring structure having first and second folded cantilever leaf spring portions coupled to the region to receive the force to be measured. The first and second leaf spring portions extend outwardly from, and are angularly displaced with respect to each other, around an axis of sensitivity. Each folded cantilever leaf spring portion includes first and second generally parallel elongated leg portions extending outwardly from the axis of sensitivity with each of said leg portions being coupled together at the outer end by a coupling structure which is free to move both parallel to and perpendicular to the axis of sensitivity in response to displacement of the inner end of one of said leg portions relative to the other along the axis of sensitivity in response to application of the force to be measured to the inner ends of the leg portions. The leg portions are dimensioned to have a higher compliance along the axis of sensitivity than the compliance thereof perpendicular to the axis of sensitivity. Differential capacitance or piezoresistance strain gauges are the preferred method for deriving an output which is proportional to the component of applied force tending to displace one of the leg portions relative to the other along the axis of sensitivity. Squeeze film damping is the preferred method of damping the composite spring structure.
Abstract:
Solid state folded leaf spring force transducers are fabricated by batch photolithographic and etching techniques from a monocrystalline material, such as silicon. The folded leaf spring structure includes elongated gaps separating adjacent leaf spring leg portions, such elongated gaps being oriented parallel to a crystallographic axis of the monocrystalline material. In a preferred embodiment the monocrystalline material is of diamond cubic type and the leaf spring gaps extend in mutually orthogonal directions parallel to the and crystallographic axes, respectively. In a preferred method of fabricating the spring structure, the structure is etched from a monocrystalline wafer by means of an anisotropic etchant so as to more precisely define angles and dimensions of the resultant spring structure. In one embodiment, the gaps between adjacent leg portions of the spring structure are sealed in a fluid tight manner by means of oxide membranes left intact upon etching of the spring structure. In an accelerometer embodiment, sensing masses of equal weight are affixed to opposite sides of the spring structure for dynamically balancing same. .Iadd.
Abstract:
An infrared laser absorption spectrometer is disclosed wherein a pair of detector cells are disposed serially along the laser beam path. The laser beam is modulated to produce a modulation of the absorption by the sample materials in the two cells. Modulated absorption by the samples produces an acoustic wave in each cell which is detected by a suitable microphone and subtracted so as to produce a difference signal corresponding to the difference in infrared absorption between the two cells so that undesired background effects common to both cells are cancelled. A pressure controller, which is responsive to the pressure difference between the sample pressure in the two cells at a frequency substantially below the beam modulation frequency is employed for controlling the pressure differential. In one embodiment the pressure controller includes a compliant membrane partitioning the two cells so that the membrane may move so as to equalize the pressures. In a second embodiment, deflection of the diaphragm of a differential microphone coupled into both cells is employed to derive an output utilized to control either the flow through the cells and/or the volume of the respective cells to control the pressure difference between the cells.
Abstract:
A percutaneous agent delivery or sampling device comprising a sheet having a plurality of microblades for piercing and anchoring to the skin for increasing transdermal flux of an agent and for improving the attachment of the device to the skin.
Abstract:
A method of producing a high resolution expanded analog gray scale mask is described. Using an inorganic chalcogenide glass, such as a selenium germanium, coated with a thin layer of silver, a gray scale mask may be produced with accurate control of the size, uniformity and variance of the pixels. The selenium germanium glass is composed of column structures arranged perpendicularly to the substrate giving a possible edge precision of 100 .ANG.. The column structures also prevent undercutting during the etching process, thus permitting pixels to be placed close together. Accordingly, selenium germanium may be used as a high resolution gray scale mask with an expanded analog gray scale. The gray scale mask may be used to impress information as a modulated thickness on a selenium germanium photoresist layer on an inorganic substrate. The selenium germanium photoresist layer may then transfer the gray scale to the substrate.
Abstract:
Miniature thermal fluid flow sensors of the airfoil type are made in batch form by forming the thermal fluid flow sensors on a thin sheet of material and bonding the sheet over an array of duct structures and dicing the individual sensors and duct structures apart. In one thermal flow sensor configuration, a flow heater is dispsoed inbetween first and second thermal flow sensors in heat exchanging relation therewith. A third thermal flow sensor is disposed upstream of the others out of heat exchanging relation with the heater for operation of the heater at a certain temperature above that sensed by the third sensor. In the low flow regime, flow is measured by the difference between the outputs of the first and second sensors, whereas in the high flow regime, the power required to maintain the temperature of the heater serves as a measure of the flow.
Abstract:
A method for manufacturing a mask (100) for use in x-ray photolithographic processes includes the step of coating a silicon wafer (10) with a layer of boron nitride (12). A masking substance (14) is used to coat one side of the boron nitride coated wafer, and the boron nitride is etched off of the other side of the wafer. The wafer (10) is then bonded to a pyrex ring (16) using a field assisted thermal bonding process. During the field assisted thermal bonding process, the silicon (11) is bonded directly to the pyrex (16). Then, a zirconium layer (24) is used to cover the mask and is selectively etched where it is desired to remove a circular portion of the silicon. Thereafter the silicon is subjected to a semianisotropic etch. The remaining structure includes a pyrex ring bonded to a silicon ring across which a layer of boron nitride is stretched. The layer of boron nitride is subjected to an annealing process and is then coated with an x-ray opaque material.
Abstract:
In a miniature valve, a valve seat is formed by aperturing a plate. A cantilever leaf spring is disposed overlying the apertured plate for controlling the flow of fluid therethrough. An electrostatic potential applied between the cantilever leaf spring and the valve plate pulls the leaf spring over the apertured plate for variably controlling flow through the valve in accordance with the magnitude of the applied potential. In a preferred embodiment, the cantilever leaf springs are made in batch form by etching a silicon wafer. A flow controller is provided by measuring the electrical capacitance of the valve, comparing it with a reference voltage and deriving a feedback voltage applied to the valve for controlling flow therethrough. In one embodiment, the width of the cantilever leaf spring valve member is narrowed toward its free end for finer control of flow.
Abstract:
In the thermal gas pressure gauge, a foil heater has a heater surface disposed in gas communication with the gas to be measured and the heater surface is thermally cycled at first and second reference frequencies to produce cyclical heating of the gaseous material adjacent the heating element. A directional microphone is disposed facing the heating element to derive signals of an amplitude determined by the amplitude of the cyclical heating effect of the gaseous material at the first and second reference frequencies. The detected signals are synchronously detected to produce a pair of dc outputs indicative of pressure in two respective pressure regimes. In an overlap pressure regime the two dc outputs are converted to digital signals which are correlated with pairs of values tabled in a read only memory for reading out a digital signal indicative of the pressure. In a low pressure regime from approximately 10.sup.-4 torr and below to the region of 1 to 10 torr, the measured pressure is independent of the molecular gas species and therefore is an absolute gauge, whereas in the higher pressure regime from 1 to 10 torr to the condensation pressure of the measured gas, the measured pressure is somewhat dependent on the molecular gas species. For measurement in the higher pressure regime, the heater and microphone are contained within a volume of the gas separated from the relatively large volume of a chamber being measured by means of an acoustic filter. The acoustic filter provides a high impedence to pressure waves at the second or higher reference frequency to avoid dissipation of the generated pressure wave to be measured within the large chamber volume. The tabled values in the read only memory permit a smooth transition of the gauge measurement from the first to the second regime.
Abstract:
A head slider for flying above a rotating magneto-optic or optical disk and an optical mechanical assembly with a fixed height above a rotating magneto-optic or optical disk contains magnetic coils and a lens plate with a diffractive optic structure for focusing laser light into a small spot on the disk. The diffractive optic structure may be a zone plate, a phase zone plate or a blazed phase zone plate or other diffractive focusing optical element. The diffractive optic structure does not require curved transparent material such as glass or a high index of refraction. The diffractive optic structure is easily manufactured using lithographic or other techniques.