Abstract: The invention provides a peristaltic pump. The pump has a cavity for receiving a rotor and a flexible conduit, the rotor engaging the flexible conduit to displace fluid therein. A conduit retainer mechanism is provided for engaging the flexible conduit to assist with retention of the conduit in the cavity against displacement resulting from engagement between the conduit and the rotor. The conduit retainer mechanism including first and second jaws opposite to one another, defining between them a passageway for receiving the conduit, wherein one of the first and second jaws are spring biased to resiliently engage the conduit.

Abstract: A pressure driven apparatus comprising a housing, at least one flexible membrane located within the housing dividing the interior of the housing into at least two chambers. At least one input or exhaust cam assembly operates in conjunction with the at least one flexible membrane to provide an expansion zone within the housing. Fluid enters the housing producing movement of the flexible membrane. The flexible membrane is connected to a drive member such that the movement of the fluid within the expansion zone results in the membrane imparting a force to the drive member. The flexible membrane includes seals used to maintain a dynamic and movable seal with respect to the housing.

Abstract: The invention provides a finger-type peristaltic pump (2) having a body (4) and a housing (6). The body contains two or more finger-type valves (16) and a processor (22) configured to operate the valves according to a predetermined temporo-spatial pattern. The housing has a passageway (18) configured to receive a conduit. The housing has a first position in which a conduit in the passageway is positioned adjacent to the valve fingers, and a second position in which a conduit in the passageway is not adjacent to the valve fingers. The invention also provides a housing for use in the pump of the invention.

Abstract: A micropump with a deformable membrane, including: a first chamber, one wall of which includes a first deformable membrane portion and an actuator of the first membrane portion; a second chamber including a second deformable membrane portion and a third chamber, including a third deformable membrane portion, the second chamber and the third chamber being connected together through a first channel, at least one of the second and third chambers being connected through a second channel to the first chamber; each of the second chamber and third chamber including a mechanism forming a detection gauge, but not including an activation mechanism.

Abstract: A fluid transporting device includes an elastic tube, a tube frame that holds the elastic tube in an arc, a rotary push plate arranged in the arc for facilitating fluid flow inside the elastic tube, and a plurality of push pins disposed between the elastic tube and the center of the arc. Each push pin includes a semispherical end portion that contacts the rotary push plate, a pushing end portion that places a bias on the elastic tube, and adjacent end portions of at least two push pins close the elastic tube when the semispherical end portions are pushed by an outer circumference arc of the rotary push plate.

Abstract: Provided is a fluid pumping device, and more particularly, a fluid pumping device capable of being used in fuel cell systems and the like and spatially separating a fluid temporary storage unit through which a fluid at high temperature passes from a pump, thereby maintaining the durability of the pump, facilitating replacement and management, and achieving a reduction in weight.

Abstract: Arrangements for connecting a fluid carrying tube to a peristaltic pump and/or a patient are disclosed. In some aspects, the disclosure provides arrangements that prevent the misloading of a tube in a peristaltic pump and/or misconnection of a tube to the patient that may cause a peristaltic pump to pump fluid in an undesired direction (e.g., unintentionally into or out of a patient). Tubing securing clip arrangements are disclosed as well as kits comprising tubing and clips. Other embodiments are disclosed.

Abstract: The invention provides, in various embodiments, systems, devices and methods relating to ex-vivo organ care. In certain embodiments, the invention relates to maintaining an organ ex-vivo at near-physiologic conditions.

Abstract: A fluid transporting apparatus includes a plurality of fingers arranged along a transporting direction in which fluid is transported by a tube having elasticity, the fingers reciprocatingly moving to compress or release the tube, and a driving section configured to move the plurality of fingers in a compressing direction. The fingers move in the compressing direction and crush the tube with ends of the fingers to transport the fluid on the inside of the tube in the transporting direction. The shape of the crushed tube is restored to fill the fluid in the inside of the tube. In a releasing action, in a state in which the ends of the fingers are in contact with the tube, movement of the fingers in a releasing direction is limited to a predetermined position.

Abstract: A micropump has a tube unit including a tube and a plurality of fingers, and a control unit including a cam. The tube unit is coupled to the control unit. The control unit encases the tube unit.

Abstract: The invention relates to a pump, especially usable as a peristaltic pump in an apparatus for blood treatment, wherein it is provided with at least a hammer element which interacts with at least one tube portion in which a fluid to be pumped flows and with motion means for said hammer element which push the hammer element against said tube portion so as to press it, the value of the stroke executed by said element not allowing the complete crushing of the tube itself.

Abstract: An extra-capillary fluid cycling unit for maintaining and cycling fluid volumes in a cell culture chamber includes a housing and a first flexible reservoir extra-capillary fluid reservoir disposed in the housing. The extra-capillary fluid reservoir is in fluid communication with a cell culture chamber. A second flexible reservoir is also located in the housing, the second flexible reservoir being in fluid communication with a pressure source. A sensor plate is movably disposed in the housing between the extra-capillary reservoir and the second reservoir, wherein the second reservoir is pressurized to move the sensor plate in relation to the extra-capillary reservoir to cause fluid cycling and maintain fluid volumes in the cell growth chamber.

Abstract: A peristaltic pump includes a plurality of effecters, actuated in a periodic manner upon by obstructive forces of a flexible infusion tube so as flow of infusion fluid is provided along said infusion tube, the magnitude of the obstructive forces being dependent upon the displacement of said moving effecters; and a plurality of balancing magnets providing balancing forces upon one or all the moving effecters, the balancing forces at each point along the path of motion of the moving effecters being of approximately equal magnitude to that of the obstructive forces at the point; such that the parasitic output due to work performed against the obstructive forces is approximately zero and yield is maximized.

Abstract: A system for generating a mechanical wave is disclosed. The system comprises a camshaft having plurality of rotatable cams, serially mounted on a shaft along an axis of an elastic tubular shell to form a varying phase angle along the shaft. The system further comprises a plurality of cam followers arranged circumferentially about each cam, such that a rotary motion of the cams generates a linear motion of the cam followers to radially bias in internal wall the shell. The variation of the phase angle is selected to generate a three-dimensional traveling wave along the shell.

Abstract: A method of fluid delivery from a rotary peristaltic pump is provided. It comprises providing a roller assembly having a plurality of rollers, the roller assembly having at least one anomalous range and determining a rotational position of the plurality of rollers. The method further comprises increasing a speed of the plurality of rollers when at least one of the plurality of rollers are in the anomalous range and decreasing the speed of the plurality of rollers when each of the plurality of rollers are outside the anomalous range.

Abstract: A micropump includes: a tube unit which includes a tube having elasticity and a circular-arc-shaped part, a plurality of fingers extending in radial directions from the circular-arc center of the circular-arc shape of the tube, and a tube guide frame which holds the tube and the plural fingers; a control unit which includes a cam for sequentially pressing the plural fingers from the fluid flow-in side to the fluid flow-out side of the tube, a rotor for giving rotational force to the cam, and an oscillator having a piezoelectric element and a projection disposed at an end in the longitudinal direction to contact the rotor; a reservoir which communicates with a flow inlet portion of the tube; a control circuit unit which inputs a drive signal to the piezoelectric element; and a power source which supplies power to the control circuit unit, wherein the tube unit is attachable to and detachable from the control unit substantially in the horizontal direction with respect to the rotation flat plane of the cam, and

Abstract: A micropump including a tube unit and a control unit. The control unit has a plurality of fingers. A cam sequentially presses the plurality of fingers from an inlet side to an outlet side of the tube. A drive unit gives rotation force to the cam, a control circuit unit controls operation of the drive unit, and a device frame holds the plurality of fingers, the cam, the drive unit, and the control circuit unit. A reservoir communicates with an inlet port of the tube; and a power source supplies power to the control circuit unit, wherein the tube unit is detachably attached to the control unit substantially in the horizontal direction with respect to the rotation surface of the cam and attached to the inside of a space produced by the device frame.

Abstract: A micropump including a tube unit including an elastic tube disposed in an arc shape, a plurality of fingers disposed radially from the arc shape of the tube, and a guide frame, which holds the tube and the plurality of fingers. The micropump also includes a control unit including a cam that presses the plurality of fingers, a drive section that applies torque to the cam, a control circuit that carries out a drive control of the drive section, and a machine casing that holds the cam, drive section, and control circuit. The tube unit is mountable in and removable from the control unit in a direction approximately parallel to the plane of rotation of the cam, and is mounted inside a space provided in the machine casing.

Abstract: A pump unit which can be made to be small-sized, and which enables to achieve a sufficient flow and an endoscope apparatus using such pump are provided. The pump unit which transports a fluid in a channel upon generating a progressive wave which is propagated in a longitudinal direction of the channel, in a first flexible thin film which constitutes at least a part of a channel-wall surface, includes a vibration exciter unit.

Abstract: A pumping mechanism is disclosed that includes a plurality of peristaltic pumping actuators configured to selectively and sequentially compress adjacent portions of a first portion of an at least partially compressible pumping element having an inlet that is upstream of an outlet. The plurality of pumping actuators are further configured to reciprocate at a common drive frequency with a first phase offset between each adjacent pair of pumping actuators. The pumping mechanism also includes at least one compensation actuator arranged to selectively compress a second portion of the at least partially compressible pumping element that is disposed between the first portion and the outlet. The at least one compensation actuator is configured to reciprocate at an optimal displacement and at a modulation frequency that is an integer multiple of the fundamental drive frequency and with a second phase offset between the at least one compensation actuator and the adjacent pumping actuator.

Abstract: A fluid dispensing apparatus includes an operable peristaltic pump. The pump supports a rigid container which includes an aggressive fluid which is to be dispensed from the container. A vent tube and a dispensing tube extends from the container through the pump. Operation of the pump causes fluid to be pumped out from the container through the dispensing tube while air is pumped into the container through the vent tube. This equalizes pressure in the container and allows fluid to be dispensed from a rigid container.

Abstract: A pair of gripping frame e hingedly connected together at one end thereof. Cooperating rollers are rotatably coupled to the gripping members adjacent the hinge therebetween. The rollers are positioned adjacent one another whereby a uniform space is created between the parallel, aligned surfaces of the rollers which are adapted to receive flexible fluid-filled tubing connected to a blood donor bag. When the gripping frame members are positioned adjacent one another, the aligned surfaces of the rollers will fully compress the surfaces of the tubing. Opposed crimping heads coupled to the gripping frame members are adapted to crush a securing clip disposed about the tubing thereby sealing the fluid-filled tubing when the heads are positioned adjacent one another.

Abstract: A an infusion tube misfitting detection device for an infusion pump, which can be implemented at a low cost while maintaining safety. When a door unit is to be closed with respect to a pump body in a misloaded state of an infusion tube, a mislead detection inner door is pressed by the infusion tube to operate on a handle lock part provided to a handle. Accordingly, a claw portion of the handle lock part is pushed up, so that the door unit cannot be locked with the pump body 10 by inserting the claw portion into a rectangular through-hole 11c of a base plate. Therefore, the misloaded state can be identified.

Abstract: System and method for dispensing product to a washing machine. A chemical dispensing system includes a system controller, machine interface, and pump controller that communicate through serial data buses. The system controller provides a user interface, retrieves washing machine status information from the machine interface, and issues product dispensing commands to the pump controller. The pump controller monitors pump status and dispenses product in response to commands from the system controller. The pump controller: (1) determines pump activation periods based on calibration data stored in a pump controller memory; (2) tracks pump usage and adjusts the activation period to compensate for pump wear as the pump ages; (3) disables the pump if conditions exists that preclude operating the pump; (4) monitors product levels, and (5) reports pump status to the system controller. Integral channels are included in the pump housing to provide stress relief to a squeeze tube.

Abstract: A peristaltic pump having a plurality of pressors which compress a tube portion according to an orderly sequence. The pump is capable of determining a fluid flow inside the tube portion. The pressors are balancing or tilting pressors pivoted around a mutual axis and operated by corresponding motion means, which push the pressors against a plane or reaction element, contrasting the pressure of the same pressors on the tube containing the fluid to be pumped.

Abstract: A pumping segment having a low shut-off force is disclosed. The pumping segment includes a tube having an interior surface with at least two notches on opposite sides of the interior surface.

Abstract: The present invention provides such pumping apparatuses that have very little deviation and high stability in pumping flow. A pumping apparatus comprises two members that are set along a longitudinal direction of a tube made of an elastic material with a relation that the space formed by grooves made in the two members holds the tube. The two members have reciprocal motion such that at least one of the two opposing members shuttles in parallel with the other opposing member and has a move-in motion such that at least one of the two opposing members vertically moves to the opposing surfaces of the other opposing member so that surrounding part of the groove thereof moves into an inner space of the groove of the other opposing member, by which motion the liquid in the tube is discharged from the tube by the deformation of tube cross sectional shape.

Abstract: In a pump, a flexible tube passes through the pump and is held “normally closed” at an output constriction. The pump includes a pump body and a pump member that can perform two functions by their relative motion. The first function is to open and close an input constriction of the flexible tube. The second function is to compress the section of flexible tube between the input constriction and the output constriction. This section of tube acts as the pump chamber. When closed, the input constriction provides a greater impediment to fluid flow than the output constriction. Therefore, when the input constriction is closed and the pump chamber is compressed, fluid flows out of the pump past the output constriction. When the input constriction is open and compression of the pump chamber is removed, the output constriction closes and fluid can enter the pump by flowing past the location of the input constriction.

Abstract: A cell culture system for the production of cells and cell derived products includes a reusable instrumentation base device incorporating hardware to support cell culture growth. A disposable cultureware module including a cell growth chamber is removably attachable to the instrumentation base device. The base device includes microprocessor control and a pump for circulating cell culture medium through the cell growth chamber. The cultureware module is removably attached to the instrumentation base device. Cells are introduced into the cell growth chamber and a source of medium is fluidly attached to the cultureware module. Operating parameters are programmed into the microprocessor control. The pump is operated to circulate the medium through the cell growth chamber to grow cells or cell products therein. The grown cells or cell products are harvested from the cell growth chamber and the cultureware module is then disposed.

Abstract: An infusion pump uses an improved shuttle mechanism to more reliably pump liquids in low volumes for medical and other purposes. The improved shuttle uses linear translation and wider, symmetric jaws to grasp infusate tubing and pump liquid infusate through the tubing. Adjustment of the linear motion allows a user to also adjust a pumping volume of the infusion pump. Other shuttles with wider jaws may also pump infusate using a rotary motion. In addition, more than one shuttle, such as two or three shuttles, may be used to approximate continuous pumping. A series of several smaller linear shuttles with sequential actuation may be used as a linear peristaltic pump for general peristaltic pump applications.

Abstract: This invention discloses a peristaltic pump composed of a two-stage linear peristaltic pump mechanism, which engages in different functions, charging and pumping a fluid to a patient. This peristaltic pump is capable of restoring the crushed tubing, caused by repeated compression or crushing of the tubing by peristaltic fingers, to its original circular cross sectional area so that it can provide a precise flow rate. The two-stage linear peristaltic pump mechanism substantially improves the consistency of a flow rate over time and extends the usefulness of peristaltic pumps to applications where they could not otherwise be used.

Abstract: The invention relates to a peristaltic system (50), which comprises at least two pumps (30, 30?) that can be separately actuated, each pump comprising a pump chamber (14) suited for receiving a fluid, a pump element (16) suited for suctioning and displacing a fluid into and from the pump chamber (14), two check valves (12, 12?), one of which (12) is in fluid connection with an inlet of the pump chamber (14) and the other (12?) is in fluid connection with an outlet of the pump chamber (14), and a valve (18) which is closed in the idle state of the pump (30, 30?) and in fluid connection with the check valves (12, 12?). The peristaltic system (50) further comprises a container (40) suited for receiving a fluid, the container being in fluid connection with an inlet of the one pump (30?) and with an outlet of the other pump (30) and flexibly designed at least in some regions such that the volume of the container depends on the volume of a fluid that is received.

Abstract: A peristaltic pump, for propelling liquid through a flexible pump tube, includes an outer casing having a guiding channel wherein an operating portion of the pump tube extends along the guiding channel. The peristaltic pump further includes at least two pressuring rollers supported at the outer casing in a radially movable manner which can move outwardly to press against the operating portion of the pump tube. A center driving mechanism is supported at a center portion of the outer casing to radially push the pressure rollers and to drive the pressuring rollers to concurrently rotate such that the pressuring rollers roll against the operating portion of the pump tube for continuously propelling the fluid in the pump tube in the direction of rotation.

Abstract: A microfluidic device is described. The microfluidic device comprises at least one transport channel and at least one working chamber, wherein the at least one transport channel and the at least one working chamber are separated from each other by a common deformable wall. The at least one transport channel is for containing a transport fluid and the at least one working chamber is for containing a working fluid. The microfluidic device comprises at least one pair of electrodes for changing the pressure on the working fluid such that when the pressure on the working fluid is changed, the deformable wall deforms, resulting in a change of the cross-section of the at least one transport channel. The working chamber comprises a flexible wall different from the common deformable wall and at least one electrode of the at least one pair of electrodes is provided on the flexible wall.

Abstract: Disclosed is a low cost, disposable, infusion pump. The infusion pump can include an integrated occlusion detector that detects both upstream and downstream occlusions in an infusion tube. In addition, the infusion pump can easily monitor flow rates through the infusion tube, and be quickly set to infuse at a pre-determined rate. An armature within the infusion pump works in concert with a pair of tubing pinchers to precisely control the movement of fluid within the tubing. Sensors mounted within the device detect the position of the armature and can determine if an occlusion has occurred in the tubing.

Abstract: A micropump includes: a fluid suction tube for suctioning fluid; a pumping tube connected to the fluid suction tube and providing a suction force and a discharge force to surroundings while repeatedly being expanded and contracted by an external signal; a deform tube connected to the pumping tube and having an aperture that is deformed by the suction force and the discharge force of the pumping tube; and a fluid discharge tube connected to the deform tube and discharging fluid.

Abstract: A peristaltic pump with a removable pump race module has guiding channels for receiving at least a portion of a flexible fluid-carrying tubing and an adjusting device for displacing a flexible inner portion of the removable pump race module to change the compression on the fluid-carrying tubing. The arrangement of the various elements makes it particularly suitable in configurations where compactness and convenience are important considerations.

Abstract: Rotary axial peristaltic pumps, related methods and components. The rotary axial peristaltic pump generally comprises a platen having a platen surface, a tube positioned adjacent to the platen surface, cam that rotates about a rotational axis and has a cam surface that is spaced apart from the platen surface and a plurality of tube compressing fingers. The fingers move axially back and forth in sequence to sequentially compress segments or regions of the tube against the platen surface, thereby causing peristaltic movement of fluid through the tube. The fingers move back and forth on axes that are substantially parallel to the axis about which the cam rotates.

Abstract: A peristaltic pumping system comprises a flexible tube, a substantially cylindrical rotating roller unit containing a series of rollers which are freely rotating around their axes and freely moving along a radial segment, holding mechanism for commonly holding the rollers, a central spreader element for pushing the rollers against the flexible tube and a driving unit comprising a driving coupling element, and the holding mechanism is made of at least one planar element having retaining and guiding means for rollers, and the planar element is furthermore adapted to be directly coupled to the coupling element in such a way that rollers are driven through the planar element.

Abstract: This disclosure concerns rotary axial peristaltic pumps, related methods and components. The rotary axial peristaltic pump generally includes a platen having a platen surface, a tube positioned adjacent to the platen surface, a cam that rotates about a rotational axis and a cam surface that is spaced apart from the platen surface and a plurality of tube compressing fingers. The fingers move axially back and forth in sequence to sequentially compress segments or regions of the tube against the platen surface, thereby causing peristaltic movement of fluid through the tube. The fingers move back and forth on axes that are substantially parallel to the axis about which the cam rotates.

Abstract: A tube-positioning system for loading tubing into a peristaltic pump includes a holder and a first tube segment. The holder includes a shell configured to slidably fit onto an exterior of a pump and a pair of guides extending upward from opposite side walls of the shell. The first tube segment has a fixed length and extends between the pair of guides with each end of the first tube segment secured within one of the respective guides.

Abstract: The invention relates to a microfabricated device for the rapid detection of DNA, proteins or other molecules associated with a particular disease. The devices and methods of the invention can be used for the simultaneous diagnosis of multiple diseases by detecting molecules (e.g. amounts of molecules), such as polynucleotides (e.g., DNA) or proteins (e.g., antibodies), by measuring the signal of a detectable reporter associated with hybridized polynucleotides or antigen/antibody complex. In the microfabricated device according to the invention, detection of the presence of molecules (i.e. Polynucleotides, proteins, or antigen/antibody complexes) are correlated to a hybridization signal from an optically-detectable (e.g. fluorescent) reporter associated with the bound molecules. These hybridization signals can be detected by any suitable means, for example optical, and can be stored for example in a computer as a representation of the presence of a particular gene.

Abstract: An infusion tube misloading detection mechanism for an infusion pump is provided at a low cost with a safety feature of detecting misloading of infusion tube. When a door unit is to be closed with respect to a pump body in a misloaded state of an infusion tube, a misload detection inner door is pressed by the misloaded infusion tube. Accordingly, an interlock part is prevented from being closed with the pump body. Therefore, the misloaded state can be easily identified.

Abstract: The present disclosure provides a linear peristaltic pump that is capable of dispensing varied amounts of liquid from a tube. The linear peristaltic pump includes an adjustably attached squashing plate that is configured to move lengthwise in the housing of the pump. The amount of liquid dispensed from a tube disposed in the pump varies based on the location of the squash plate in the housing.

Abstract: The invention relates to a pump chamber (1) for a peristaltic pump, the pump chamber (1) comprising an elongate cavity (1.1) defined between an elastically deformable chamber wall (1.2) and a rigid chamber (1.3) wall, wherein the elastically deformable wall (1.2) and the rigid wall (1.3) are arranged as a one-piece part by two-component injection moulding. The invention also refers to a method for producing the pump chamber (1) for a peristaltic pump, the method comprising a two-component injection moulding of the elastically deformable wall (1.2) and the rigid chamber wall (1.3) thereby forming them as a one-piece part.

Abstract: The invention-based pump module (1) comprising a base (2) and a flexibly deformable membrane (4), wherein the base (2) and the membrane (4) form a line-shaped pump channel (5) that is curved at least in sections, and the base (2) comprises a pump channel inlet (6) and a pump channel outlet (7), wherein the pump channel inlet (6) and the pump channel outlet (7) are connected with the pump channel (5) for supplying and discharging a fluid in the pump channel (5) in such a way, so that through a periodically rotating deformation of the membrane (4) a fluid can be pumped through the pump channel (5) from the pump channel inlet (6) to the pump outlet (7).

Abstract: A fluid transporting device includes an elastic tube, a tube frame that holds the elastic tube in an arc, a rotary push plate arranged in the arc for facilitating fluid flow inside the elastic tube, and a plurality of push pins disposed between the elastic tube and the center of the arc. Each push pin includes a semispherical end portion that contacts the rotary push plate, a pushing end portion that places a bias on the elastic tube, and adjacent end portions of at least two push pins close the elastic tube when the semispherical end portions are pushed by an outer circumference arc of the rotary push plate.

Abstract: In a peristaltic medical infusion pump unit, comprising a peristaltic assembly and a counter surface or anvil facing said peristaltic assembly and provided by the inner surface of a door pivotally mounted on a housing of the unit, the door is readily non-destructively removable and replaceable. In use of the peristaltic pump unit, a flexible resilient tube forming part of a medical fluid delivery line is extended between the peristaltic assembly and the counter surface or anvil provided by the door. The medical fluid delivery line has first and second color coded fittings spaced therealong upstream and downstream of the peristaltic assembly and the region of the housing of the pump unit across which the infusion line is extended is provided, correspondingly spaced above and below the peristaltic assembly with correspondingly color coded support means for these fittings.

Abstract: A fluid conveying device includes: a tube; a cam having protrusions; fingers arranged along the tube between the tube and the cam; a driving rotor which rotates the cam to sequentially push the fingers by the protrusions in a flowing direction of a fluid, repeatedly pressuring and opening of the tube, driving the cam; a detection unit which detects a rotating position of the cam; a control unit which calculates a cam rotation angle along a cumulative ejection volume, using a first approximation formula for an ejection area H where the cumulative ejection volume increases substantially in proportion to the rotation angle of the cam and a second approximation formula for a constant area J where the cumulative ejection volume little increases or decreases even if the cam rotates, driving the driving rotor until a rotating position of the cam corresponding to a designated cumulative ejection volume is reached.

Abstract: Described herein is an infusion pump with an integrated permanent magnet. The permanent magnet is positioned to provide an attractive force that moves an armature to compress a fluid-filled infusion tube. An electromagnet can be activated to overcome the attractive force of the permanent magnet and move the armature away from the infusion tubing. The force required to overcome the permanent magnet is much less than the force required to compress the tubing. For this reason the infusion pump has very low power consumption since much of the pumping work is provided by the permanent magnet.