Miniaturized fluid flow regulating device

Abstract

The invention relates to a miniaturised fluid flow regulating device comprising a fluid flow channel with an inlet portion, an outlet portion and a flow regulation passage between the inlet portion and the outlet portion, an elongated beam element arranged in the flow channel, such that a pressure difference over the inlet portion and the outlet portion causes the beam element to bend and regulate fluid flow in the flow regulation passage. The invention further relates to a breath analysis device comprising such a flow regulating device for regulating a flow of exhaled breath.

Claims

1. A miniaturised fluid flow regulating device comprising a fluid flow channel with an inlet portion, an outlet portion and a flow regulation passage between the inlet portion and the outlet portion, an elongated beam element arranged in the flow channel, such that a pressure difference over the inlet portion and the outlet portion causes the beam element to bend and regulate fluid flow in the flow regulation passage, wherein the elongated beam has a first end portion and a second end portion and extends from the inlet portion to the outlet portion of the flow channel, wherein the device comprises supporting means, wherein at least one of the first and second end portions are supported in the device by the supporting means, and wherein the supporting means is configured such that a position of support by the supporting means on the beam moves towards the flow regulation passage upon increased deflection of the beam.

2. The miniaturised fluid flow regulating device according to claim 1, wherein the supporting means is configured to effectively shorten the unsupported length of the elongated beam upon increasing deflection of the beam, thereby stiffening the beam.

3. The miniaturised fluid flow regulating device according to claim 1 wherein the supporting means comprises a ridge extending along the elongation of the beam.

4. The miniaturised fluid flow regulating device according to claim 1 wherein the supporting means comprises one or more discrete supports.

5. The miniaturised fluid flow regulating device according claim 1 wherein the supporting means comprises a first and a second ridge extending along the elongation of the beam, and arranged at a first and a second lateral side of the beam.

6. A miniaturised fluid flow regulating device comprising a fluid flow channel with an inlet portion, an outlet portion and a flow regulation passage between the inlet portion and the outlet portion, an elongated beam element arranged in the flow channel, such that a pressure difference over the inlet portion and the outlet portion causes the beam element to bend and regulate fluid flow in the flow regulation passage, wherein the elongated beam has a first end portion and a second end portion and extends from the inlet portion to the outlet portion of the flow channel, wherein the device comprises supporting means comprising a first and a second ridge extending along the elongation of the beam, wherein at least one of the first and second end portions are supported in the device by the supporting means, and wherein the first and second ridges are curved, such that the position of the support along the elongated beam from the ridges is continuously dependent on the degree of deflection of the beam.

7. The miniaturised fluid flow regulating device according to claim 6 wherein the elongated beam has a length in the range of 5-20 mm, preferably 5-15 mm, and/or a width in the range of 2-10 mm, preferably 4-6 mm, and/or a thickness in the range of 10-500 m, preferably 30-300 m.

8. The miniaturised fluid flow regulating device according to claim 6 wherein the flow channel has a width in the range of 2-10 mm, preferably 4-6 mm, and/or a height in the range of 0.1-2 mm, preferably 0.5-1 mm.

9. A breath analysis device comprising a miniaturised flow regulating device according to claim 6 for regulating a flow of exhaled breath to maintain a flow in the range of 10-300 ml/s, preferably maintaining a flow of 505 ml/s, and preferably over a pressure range of 1000 Pa.

10. The breath analysis device according to claim 9 comprising a sensor for analysing the concentration of nitric oxide, NO, in exhaled breath.

11. A method for regulating a flow of exhaled breath in a breath analysis device to maintain a flow in the range of 10-300 ml/s, over a pressure range of 1000 Pa, wherein the breath analysis device includes a fluid flow channel with an inlet portion, an outlet portion and a flow regulation passage between the inlet portion and the outlet portion, an elongated beam element arranged in the flow channel, such that a pressure difference over the inlet portion and the outlet portion causes the beam element to bend and regulate fluid flow in the flow regulation passage, wherein the elongated beam has a first end portion and a second end portion and extends from the inlet portion to the outlet portion of the flow channel, wherein the device comprises supporting means comprising a first and a second ridge extending along the elongation of the beam, wherein at least one of the first and second end portions are supported in the device by the supporting means, and wherein the first and second ridges are curved, such that the position of the support along the elongated beam from the ridges is continuously dependent on the degree of deflection of the beam, the method comprising: deflecting the elongated beam toward the supporting means by pressure exerted by the flow of exhaled breath.

12. A method for regulating a flow of exhaled breath in a breath analysis device to maintain a flow of 505 ml/s over a pressure range of 1000 Pa, wherein the breath analysis device includes a fluid flow channel with an inlet portion, an outlet portion and a flow regulation passage between the inlet portion and the outlet portion, an elongated beam element arranged in the flow channel, such that a pressure difference over the inlet portion and the outlet portion causes the beam element to bend and regulate fluid flow in the flow regulation passage, wherein the elongated beam has a first end portion and a second end portion and extends from the inlet portion to the outlet portion of the flow channel, wherein the device comprises supporting means, wherein at least one of the first and second end portions are supported in the device by the supporting means, and wherein the supporting means is configured such that a position of support by the supporting means on the beam moves towards the flow regulation passage upon increased deflection of the beam, the method comprising: deflecting the elongated beam toward the supporting means by pressure exerted by the flow of exhaled breath.

13. A breath analysis device comprising a miniaturised flow regulating device according to claim 1 for regulating a flow of exhaled breath to maintain a flow in the range of 10-300 ml/s, preferably maintaining a flow of 505 ml/s, and preferably over a pressure range of 1000 Pa.

14. The breath analysis device according to claim 13 comprising a sensor for analysing the concentration of nitric oxide, NO, in exhaled breath.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The invention is now described, by way of example, with reference to the accompanying drawings, in which:

(2) FIG. 1 shows a miniaturised fluid flow regulating device according to an embodiment, in a cut-away perspective view.

(3) FIG. 2 shows part of a miniaturised fluid flow regulating device according to an embodiment, in perspective view.

(4) FIG. 3 shows a miniaturised fluid flow regulating device according to an embodiment, in a cross-sectional view.

(5) FIG. 4 shows part of a miniaturised fluid flow regulating device according to an embodiment, in perspective view.

(6) FIG. 5 shows a miniaturised fluid flow regulating device according to an embodiment, in a cross-sectional view.

(7) FIG. 6 shows the deflection of the beam element. It can be seen that the deflection of the beam element decreases, i.e. the beam element becomes harder and harder as the pressure increases. First 5000 Pa give a deflection of about 202 m, further +5000 Pa gives +106 m deflection, still further +5000 Pa gives +51 m deflection, and yet still further +5000 Pa gives +12 m deflection. The upper curve shows the deflection expressed in pm and the lower curve shows the resulting flow in ml/s. The scale is the same to the left.

DESCRIPTION OF EMBODIMENTS

(8) In the following, a detailed description of embodiments of the miniaturised fluid flow regulating device is described with reference to the drawings.

(9) In FIG. 1 a miniaturised fluid flow regulating device 1 is shown, cut in half. The device comprises a fluid flow channel 2 with an inlet portion 3, an outlet portion 4 and a flow regulation passage 5 between the inlet portion and the outlet portion. The device is assembled by a first 6 and a second 7 part of material, forming a housing of the device. The material may e.g. be a polymer material. The device may comprise a first 8 and second 9 connector for connecting the device to e.g. tubing.

(10) The flow regulating device comprises an elongated beam element 10 arranged in the flow channel 2 having the direction of elongation along the fluid flow channel. The elongated beam has a first end portion 13 and a second end portion 14 and extends between the inlet portion to the outlet portion of the flow channel.

(11) The elongated beam comprises a first 11 and a second 12 face. The second face 12 of the elongated beam defines a wall in the flow regulation passage. The first end portion 13 of the beam is clamped in the device, e.g. by integrally forming the elongated beam in the same piece of material as the device itself or by rigid attachment to the material of the device. The second end portion 14 of the beam not supported, forming a free end. Thus, in this embodiment the beam is formed as a cantilever. A fluid space 15 is formed in the device communicating with the inlet portion of the fluid flow channel. The first face 11 of the elongated beam defines a wall in the fluid space. The fluid space is further delimited by the attachment of the first end 13 of the elongated beam.

(12) In FIG. 1 the supporting means supporting the at least one of the first and second end portion are not shown.

(13) In FIG. 2 the first part of material 6 forming part of the fluid regulating device is shown. The elongated beam 10 is now shown with the second face 12 facing the viewer. In this example the elongated beam is supported in the device by being integrally formed in the same piece of material as the first part 6. Thus the beam is clamped at the first end portion 13. The lateral sides of the beam (perpendicular to the elongation of the beam) are free to move, and thus slits 16a and 16b are formed along the sides of the elongated beam. These slits provides for a controlled but minimised leakage flow from the fluid space into the flow channel and towards the outlet portion of the flow channel. This leakage flow may be limited by designing the slits and e.g. by providing a ridge under and/or over the elongated beam to increase the pressure drop over the slits.

(14) In FIG. 2 the supporting means supporting the at least one of the first and second end portion are not shown.

(15) The first part of material 6 may be provided with protrusions 17 and/or indentions 18 to provide alignment and tight fitting of the first and second parts of material.

(16) FIG. 3 further shows the fluid regulating function of the device. The inlet portion 3, outlet portion 4 and flow regulation passage 5 of the flow channel is shown. From this drawing it is evident that the fluid space 15 is arranged such that the first face 11 of the beam 10 is subjected to fluid pressure communicating with the inlet portion 3 of the fluid flow channel. Thus a pressure difference acting on the first 11 and second 12 face of the elongated beam causes the beam element to bend and regulate fluid flow in the flow regulation passage. In particular, a higher pressure in the inlet portion (and thus the fluid space 15) than in the flow regulation passage 5 causes the elongated beam to bend towards the flow regulation passage to decrease the cross-sectional area of the flow regulation passage. Thereby the flow resistance in the flow regulation passage is increased, limiting the flow speed of the fluid passing the flow regulation passage.

(17) In FIG. 3 the supporting means supporting the at least one of the first and second end portion are not shown.

(18) In FIG. 4 an embodiment of a miniaturised fluid flow regulating device is shown. In FIG. 4 the configuration and support of the elongated beam is shown. FIG. 4 shows a part 7 of the device with an inlet portion 3, an outlet portion 4 and a flow regulation passage 5 between the inlet portion and the outlet portion. At the flow regulation passage a number of supporting means are provided to support an elongated beam element placed thereon (not shown). The supporting means comprises a first 19a and a second 19b discrete support arranged in the middle of the flow channel, towards the inlet and outlet portion respectively. Further, the supporting means comprises a first 20a and a second 20b ridge arranged along each side of the flow channel, to provide support along the lateral sides of the elongated beam. The ridges are also formed to limit the leak flow through slits formed between the elongated beam and lateral walls of the flow channel.

(19) The ridge supports may be provided with a shape that provides support along the elongated beam upon deflection of the beam. The shape of the ridge may be such that the support position along the beam is continuously dependent on the deflection of the beam thereby effectively shortening the unsupported length of the elongated beam upon increasing deflection of the beam. This has the effect to stiffening the beam gradually (or stepwise) upon deflection.

(20) In FIGS. 5a and 5b the operation of the device is shown. The fluid space 15 is arranged such that the first face 11 of the beam 10 is subjected to fluid pressure communicating with the inlet portion of the fluid flow channel. The elongated beam is simply supported on the supporting means comprising a ridge 20. A pressure difference acting on the first 11 and second 12 face of the elongated beam causes the beam element to bend and regulate fluid flow in the flow regulation passage.

(21) In the example shown the ridge is V-shaped. This has the effect that the elongated beam initially is simply supported at the first and second end portion until the deflection of the beam is such that they tangent the V-shaped support (as shown in FIG. 5b). Thereafter any further deflection will result in the position of the support being moved towards the center of the V-shaped ridge. By moving the position of the support towards the center of the V-shaped ridge the effective length of the deflected beam will decrease, thereby increasing the stiffness of the beam.

(22) The shape of the supporting means may thus be adapted to provide an increasing stiffness upon deflection, thus adapting the flow regulation in the flow regulation passage to a desired pressure-flow behavior. The supporting means may be in the form of a ridge having a V-shape, a gull-wing shape, a curved shape, a sinusoidal shape etc, or in the form of distributed discrete supports of different heights adapted to provide support upon increasing deflection.

(23) The material of the beam may be selected to a material other than the material of the parts forming a housing, e.g. single crystalline silicon, metal etc. The material is preferably selected from a group of materials having a high fatigue strength.

(24) The device comprises a cantilever that constitutes one of the walls in the flow regulation channel, as can be seen in FIG. 1. When a pressure is applied at the inlet, the inlet pressure will act along the full length of the first face of the cantilever. A flow in the narrow flow regulation channel beneath the cantilever will result in a pressure drop resulting in a net force distribution along the length of the cantilever, causing it to bend down and restrict the flow in the channel, as can be seen in FIG. 3.

(25) The spring force of the cantilever (the elongated beam) effectively balances against the flow induced downward bending forces acting on it, resulting in a predictable deflection at any inlet pressure. In addition to the primary cantilever-controlled flow, a leak flow occurs which may be utilized to avoid too much flow restriction.

(26) The total pressure drop in the device may be approximated and divided into three regions: a sudden contraction region where the flow meets the tip of the cantilever, a diffuser region along the length of the cantilever and a sudden expansion region at the exit, as shown FIG. 3. The total pressure drop caused by the cantilever restriction and the flow channel along the bottom of the cantilever may then be described by the following expression:
p.sub.c=p.sub.i+p.sub.d+p.sub.o
where p.sub.i is the inlet pressure drop caused by the sudden contraction of the flow channel, p.sub.d is the diffuser region pressure drop along the length of the cantilever and p.sub.o is the outlet pressure drop caused by sudden expansion of the flow channel.

(27) The pressure drop at these regions may be approximated by the following expressions:

(28) $p_i={}_i\frac{v_i}{2};{}_{i}0.4$$p_d={}_d\frac{v_i}{2};{}_d=1-{\left(\frac{A_i}{A_0}\right)}^2-C_p$$p_o={}_o\frac{v_i}{2};{}_o={\left(\frac{A_i}{A_0}\right)}^2$
where is the density of the fluid, .sub.i is the mean flow velocity at the contracted inlet, .sub.i, .sub.d and .sub.o are pressure loss coefficients, A.sub.i and A.sub.0 are cross sectional areas of the contracted inlet and the non-contracted channel respectively and C.sub.p is the pressure recovery coefficient.

(29) Using Bernoulli's equation it can then be shown that the main flow may be approximated by the following expression:

(30) ${}_c=\frac{\sqrt{p}}{B}\left(1-\frac{C}{B^2}p\right)$
where constants B and C are:

(31) $B=\sqrt{\frac{\left(1.4-C_p\right)}{2A_o^2}}$$C=\frac{L^4\left(21-4C_p\right)}{20{\mathrm{Eb}}^2{t}^3{h}_0^3}$
where L is the length of the cantilever, E is the elastic modulus, b and t are the width and thickness of the cantilever, respectively, and h.sub.0 is the channel height at zero cantilever deflection.

(32) The constants B and C may be optimized for a specific flow rate at two pressure levels using the following expressions:

(33) $B=\frac{\frac{P_2}{P_1}-1}{\frac{{}_1}{{}_2}{\left(\frac{P_2}{P_1}\right)}^{3/2}-1}.Math.\frac{\sqrt{P_2}}{{}_2}$$C=B^2\left(1-\frac{B{}_1}{\sqrt{P_1}}\right)\frac{1}{P_1}$
where P.sub.1 and .sub.1 are the pressure and flow rate, respectively, for the first target point and P.sub.2 and .sub.2 are the pressure and flow rate for the second target point.

(34) Assuming an ideal pressure source and no losses in the tubings connecting the device the total flow through the device may be approximated by:
=.sub.c+.sub.l; .sub.lD{square root over (p)}

(35) where .sub.l is the leak flow and D is a constant defined by the geometry of the leak gaps.