CN102678526B - The travelling-wave-type Valveless Piezoelectric Micropump of multistage diffusion microchannel - Google Patents

Abstract

The present invention proposes a kind of structure and formation method of multistage diffusion microchannel travelling-wave-type Valveless Piezoelectric Micropump.This micro-pump structure comprises: Micropump substrate, microchannel and travelling wave drive array.Micropump substrate is primarily of driving array draw-in groove, microchannel bonding region, sample inlet and outlet composition; The material of multistage diffusion microchannel is PDMS, corresponding to every one-level diffusion structure, is manufactured with corresponding trapezoidal protrusion at pipeline upper surface, and boundary dimension and diffusing tube internal diameter match, and microchannel and Micropump substrate are bonded together and form the complete pump housing; Travelling wave drive array adopts piezoelectric bimorph parallel distribution, and one end of every sheet piezoelectric bimorph to be placed in the corresponding trapezoidal protrusion in microchannel surface and close contact, and the other end is fixed in Micropump substrate.Multistage diffusion microchannel combines with travelling-wave-type Valveless Piezoelectric Micropump by the present invention, reduce the reverse reflux of Micropump pipeline, improve Micropump and export flow velocity, and have that preparation process is simple, volume is little, flow control facilitates the features such as accurate, be suitable for the manufacture of integrated microfluidic chip.

Description

The travelling-wave-type Valveless Piezoelectric Micropump of multistage diffusion microchannel

Technical field

The present invention relates to a kind of Valveless Piezoelectric Micropump of multistage diffusion microchannel, its driving mode is travelling wave drive.

Background technique

Microfluid (chip lab) technology is one of the new and high technology and multi-crossed disciplines Environment Science field that develop rapidly at present, is the important technological platform of life science, chemical science and information science input and Study on processing method.It can make the biological sample in biomedical sector and reagent consumption greatly reduce, and analysis speed significantly improves, and cost declines at double; At chemical field, it can use a small amount of sample and reagent to complete great many of experiments with the very short time on one chip simultaneously; In analytical chemistry field, it makes large analytical instrument become a square centimeter ANALYZER for size scale.Parts involved by micro-fluid chip comprise: the dialysis relevant with sample introduction and Sample handling, film, SPE, purification; For micro-valve (comprising aggressive valve and passive valve) that fluid controls, Micropump (comprising mechanical pump and on-mechanical pump); Micromixer, microreactor, also has micro passage and micro-detector etc. certainly.

Micropump, as the important power unit of micro-fluid chip fluid drive part, is the important symbol of its development level.Micropump is mainly used to provide fluid driving forces in the entire system, is responsible for control pump feeding sample, controls flow and flow velocity.The mode classification of Micropump has a variety of: according to or without movable valve block, can be divided into and have valve Micropump and valve free pump; Different according to driving mode, piezoelectricity type, electrostatic, pneumatic type, thermal drivers formula etc. can be divided into.

Have valve Micropump to be generally utilize the mechanical periodicity of cavity volume and one-way cock work, have the principle of valve Micropump simple, preparation process is comparatively ripe and be easy to control, and is the main flow of application at present.But owing to there is the mechanical parts such as valve block in the pump housing, the fatigue of valve block and life problems are puzzlement researcher's difficult problems, greatly limit its application area always; And the processing technology of these mechanical movable parts and machining precision limit the further miniaturization of valve Micropump, the technical need of the inadaptable micro-fluid chip developed rapidly in recent years.Compared valve Micropump, valve free pump is because its principle is novel, structure is relatively simple, manufacture process requirement is not high, be suitable for microminiaturization, thus has unique advantages for development and wide application prospect.

Be used in the travelling wave drive technology in valve free pump, be use piezo actuator array on elasticity microchannel, evoke the capable ripple of row, drive the pump liquid mode of liquid directional flow.This Micropump, to be added in voltage signal on piezo actuator to control flow of fluid, realizes liquid bidirectional conveying to change voltage-phase.Under this travelling wave drive mode, in microchannel, the movement locus of liquid particle is approximately elliptic motion, and after a row period of wave, liquid particle is generation minute movement compared with initial position, and this movement finally forms the directed flow of fluid of certain flow rate.

The people such as Estemme in 1993 have developed a kind of Novel contracting/expanding valve free pump, that the difformity microchannel shrinking and expand replaces movable valve block, utilize the asymmetric pumping realizing liquid of the asymmetric pressure loss caused of microchannel structure, but the reverse fluid stopping poor-performing of this kind of pump, liquid flows into simultaneously from contraction and expansion pipeline and flows out pump chamber, cause flow loss comparatively large, efficiency is lower.The valve free pump structure of this contraction/distension type is simple, novel, is suitable for the Micropump of this structure to be integrated in micro-fluidic chip.

In order to reduce the microchannel resistance of row ripple Micropump and improve Micropump output flow velocity, the present invention proposes a kind of multistage diffusion microchannel travelling-wave-type Valveless Piezoelectric Micropump.Multistage diffusion microchannel is by multiple diffusing tube structure lateral stacking, is placed in the pump district part of row ripple Micropump, and piezo actuator array is arranged on multistage diffusing tube structure upper surface, directly in microchannel, evokes row ripple.Utilize the nonsymmetry of multistage diffusing tube structure to cause the difference of convection cell resistance, reduce the resistance of liquid single direction in the duct, meanwhile, the cascade of multiple diffusing tube structure effectively can also improve the reverse fluid stopping performance of pipeline.This row ripple Micropump can only realize unidirectional pumping, but can effectively improve Peak Flow Rate and back pressure.

Summary of the invention

The object of the invention is: complicated for existing micro-pump structure, the present situation that efficiency is lower, propose a kind of multistage diffusion microchannel travelling-wave-type Valveless Piezoelectric Micropump, the feature of this Micropump is: structure is simple, and pump liquid efficiency is high, is convenient to miniaturization and Integrated manufacture.

Travelling-wave-type Valveless piezoelectric micro fluid dynamcis and control technique, be produce multiple amplitude by Drive and Control Circuit, frequency, direction of vibration are identical, and there is the drive singal of certain phase difference, electrical signal is changed into mechanical vibration by the inverse piezoelectric effect of piezo actuator, microchannel evokes row ripple, make the liquid in pipeline follow the flowing of ripple direction, this is a kind of novel micro fluid dynamcis technology.And flow rate of liquid can be controlled by the voltage of drive singal and frequency.

Piezo actuator is piezoelectric bimorph, adopts the piezoceramic material of PZTS (lead zirconate titanate), has high coupling coefficient and high-tension electricity strain constant, and electromechanical parameters has excellent time and temperature stability.Piezoelectric bimorph is a kind of transducer utilizing the horizontal inverse piezoelectric effect of piezoelectric constant to make, and adopt double-layer overlapped chip architecture, extra electric field direction and direction of vibration are mutually vertical.Its displacement can be expressed as:

$u=\frac{3d_{31}{U}_s}{4D^2}{H}^2---\left(1\right)$

Wherein, d31 is the horizontal piezoelectric crystal of piezoceramic material; Us is applied voltage; H and D is respectively length and the thickness of monolithic piezoelectric ceramic in piezoelectric bimorph.

Utilize piezoelectric bimorph chip arrays on microchannel, excite one group of amplitude, standing wave that frequency is identical, the row ripple of synthesis makes the continuous-flow in a certain direction of ducted liquid.In order to reduce the backflow phenomenon of liquid in pipeline, replace the original straight pipeline in pump district by the mode of multiple diffusing tube lateral stacking, this structure serves the effect of one-way valve, inhibits liquid reverse flow in the duct.Multistage diffusion microchannel is combined with travelling wave drive piezoelectric structure, the one-way flow of liquid can be realized, and flow velocity and back pressure improve greatly.

Row ripple is that the form passing in time of ripple is constantly pushed ahead formed in media as well in a certain direction.Be in each point of fluctuation in the vibration of its equilibrium position place, and its vibrational state, energy are propagated along the direct of travel of ripple.Have close contact between standing wave and row ripple, the standing wave that two row meet certain condition just can superpose and become the capable ripple of row.Suppose that the function of two row standing waves is:

This two row standing wave is superposed to the capable ripple of row, condition that row ripple propagates along positive x direction and negative x direction can be obtained respectively:

Above two formulas give the relation of each piezoelectric bimorph spacing and each drive singal phase difference in piezo actuator array: (θ ₂-θ ₁) (λ/2 π) be the spacing of two row standing wave anti-node location, it is the phase difference of two row standing waves.

To adopt the driving array of four piezo actuators, their amplitude, frequency, direction of vibration are identical, and phase place to differ pi/2 adj acent piezoelectric final controlling element spacing be successively that four/a line wave-wave is long, the standing wave anti-node location difference four/a line wave-wave namely on microchannel is long.The mode of its synthesis row ripple can be expressed as follows:

$y_A={\mathrm{\ϵ}}_0\sin \frac{2\mathrm{\π}}{\mathrm{\λ}}x\·\sin {\mathrm{\ω}}_{0}t---\left(6\right)$

$y_B={\mathrm{\ϵ}}_0\sin (\frac{2\mathrm{\π}}{\mathrm{\λ}}x+\frac{\mathrm{\π}}{2})\·\sin ({\mathrm{\ω}}_{0}t+\frac{\mathrm{\π}}{2})={\mathrm{\ϵ}}_0\cos \frac{2\mathrm{\π}}{\mathrm{\λ}}x\·\cos {\mathrm{\ω}}_{0}t---\left(7\right)$

$y_C={\mathrm{\ϵ}}_0\sin (\frac{2\mathrm{\π}}{\mathrm{\λ}}x+\mathrm{\π})\·\sin ({\mathrm{\ω}}_{0}t+\mathrm{\π})={\mathrm{\ϵ}}_0\sin \frac{2\mathrm{\π}}{\mathrm{\λ}}x\·\sin {\mathrm{\ω}}_{0}t---\left(8\right)$

$y_D={\mathrm{\ϵ}}_0\sin (\frac{2\mathrm{\π}}{\mathrm{\λ}}x+\frac{3\mathrm{\π}}{2})\·\sin ({\mathrm{\ω}}_{0}t+\frac{3\mathrm{\π}}{2})={\mathrm{\ϵ}}_0\cos \frac{2\mathrm{\π}}{\mathrm{\λ}}x\·\cos {\mathrm{\ω}}_{0}t---\left(9\right)$

In the elastomer, four row standing waves synthesize the capable ripple of row:

$y=y_A+y_B+y_C+y_D=2{\mathrm{\ϵ}}_0(\sin \frac{2\mathrm{\π}}{\mathrm{\λ}}x\·\sin {\mathrm{\ω}}_{0}t+\cos \frac{2\mathrm{\π}}{\mathrm{\λ}}x\·\cos {\mathrm{\ω}}_{0}t)$

$=2{\mathrm{\ϵ}}_0\cos (\frac{2\mathrm{\π}}{\mathrm{\λ}}x-{\mathrm{\ω}}_{0}t)---\left(10\right)$

The material of multistage diffusion microchannel is PDMS, and performed polymer fully mixes by 10: 1 volume ratios with curing agent, is shaped in a mold and solidifies completely.Again PDMS microchannel and Micropump substrate are bonded together, make the complete pump housing.Multistage diffusion microchannel upper surface is distributed with one group of trapezoidal protrusion, every sheet twin lamella correspondence in piezoelectric driven array is placed in each trapezoidal protrusion, spacing between piezoelectric bimorph should meet the rule of formula (4), (5), and the standing wave making it excite can synthesize the row ripple of certain orientation.In special case for formula (6 ~ 10), the spacing between piezoelectric bimorph is quarter wavelength, and wavelength X can be obtained by traveling wave speed, and the transverse wave speed v in elastomer is expressed as:

$v=\sqrt{G/\mathrm{\ρ}}---\left(11\right)$

Wherein ρ is elastomer density, and G is elastomeric shear modulus.

Each diffusing tube structure of multistage diffusion microchannel can be divided into two-part: the different diffusing opening of two subtended angles connects relatively.The angle of two diffusing opening joints is 90 °, therefore the subtended angle of two diffusing openings complementary angle each other, and one of them subtended angle is much smaller than another.In order to obtain best performance, the physical dimension of Micropump can correspondingly adjust, and the present invention is dimensional parameters used in testing: the subtended angle of two diffusing openings is about 6.5 ° and 83.5 ° respectively, single diffusing tube minimum width 200 μm, Extreme breadth 700 μm, length is about 2.2mm.

Accompanying drawing explanation

In accompanying drawing, the substrate of 1-Micropump; The multistage diffusion microchannel of 2-; 3-travelling wave drive array; 4-drives array draw-in groove; 5-microchannel bonding region; 6-sample inlet; 7-sample export; 8-microchannel formpiston; 9-microchannel former; 10-multistage diffusion microchannel Internal periphery formpiston; 11-multistage diffusion microchannel external frame former; 12-trapezoidal protrusion former; 13-trapezoidal protrusion.

Fig. 1 is Micropump overall schematic.

Fig. 2 is Micropump substrate schematic diagram.

Fig. 3 is microchannel mould formpiston schematic diagram.

Fig. 4 is microchannel mold cavity block schematic diagram.

Fig. 5 is multistage diffusion microchannel structural representation.

Fig. 6 is piezo actuator array drive signals figure.

Embodiment

The working process of Micropump and the selection of material closely related, different materials adopts different micro-processing methods.Micropump substrate and microchannel die material can adopt silicon or PMMA (polymethylmethacrylate), and silicon materials can use plasma etching industrial, mutually compatible with the MEMS technology of maturation; And PMMA has good optical property, chemical stability and mechanical property, be widely used in the structural material of Micropump, can micro-machining be used.

Use micro-machining to make Micropump substrate and the microchannel mould of PMMA material, make the piezoelectric driven array draw-in groove of 100 μm of dark microchannel bonding regions and certain depth at Micropump substrate surface; And the pipe interior of microchannel mould is high 100 μm, pipeline wall thickness 300 μm; Two subtended angles of the multistage diffusion structure in pump district are about 6.5 ° and 83.5 ° respectively, single diffusing tube minimum width 200 μm, Extreme breadth 700 μm, and length is about 2.2mm; Pipeline upper surface trapezoidal protrusion height about 120 μm, the physical dimension of projection is slightly less than microchannel Inner Dimension.If need to make the more careful microchannel of structure, the methods such as plasma etching can be adopted on silicon chip to make mould.

PDMS (dimethyl silicone polymer) then selected by the material of microchannel, and it is the main making material of microchannel in micro-fluidic technologies field.The PDMS microchannel of current micro-fluid chip, main employing injection method machines, it is high that this method has accuracy, reusable, make simple, process cycle is short, processing environment be there is no to the outstanding advantages such as particular/special requirement, it accurately can copy the microstructure of micron level, compared with traditional micro fabrication, has great advantage.

PDMS microchannel is fully mixed by a certain percentage PDMS performed polymer and curing agent, is injected in mould after vacuum outgas, and in constant temperature oven, isothermal curing certain hour obtains.Here the performed polymer of PDMS microchannel and the ratio of curing agent are 10: 1; Put into the degassed 30min of vacuum dryer after being fully uniformly mixed, degree of vacuum is 10 ^-1kg/cm ², divide afterwards and be injected in microchannel mould.Again the microchannel mould being marked with PDMS is put in the constant temperature oven of 65 DEG C, isothermal curing 30min.Now PDMS solidifies not yet completely, by the demoulding of PDMS microchannel, and (bonding region applies the PDMS film of one deck 100 μm to be in advance placed on the microchannel bonding region of PMMA Micropump substrate, the ratio of performed polymer and curing agent is 5: 1, and 10min is solidified in constant temperature oven), utilize Van der Waals force, make pipeline together with substrate adhesive.Now PDMS microchannel and substrate film all do not solidify completely, then at 65 DEG C isothermal curing 60min, make it solidify completely, be placed in drying basin stand-by afterwards.

Piezoelectric driven array one end of piezoelectric bimorph composition is fixed in the draw-in groove of substrate, and the other end is pressed in the trapezoidal protrusion of the multistage diffusion structure of pump district microchannel respectively.Piezoelectric bimorph is sinusoidal wave by four tunnels of phase difference of pi/4, square wave or triangular signal drive, and evokes row ripple, promote ducted flow of fluid in microchannel.

Claims (4)

1. the travelling-wave-type Valveless Piezoelectric Micropump of a multistage diffusion microchannel, adopt travelling wave drive array as Micropump driver part, the microchannel driving pump district below array is multistage diffusing tube structure, each piezo actuator is positioned at directly over every grade of diffusing tube, and with the trapezoidal protrusion close contact at microchannel top.

2. Micropump according to claim 1, its structure comprises Micropump substrate, microchannel and travelling wave drive array; Micropump substrate is manufactured with a microchannel bonding region, a sample inlet, a sample export and a driving array draw-in groove; The pump district, middle part of microchannel is the multistage diffusing tube structure of lateral stacking, and the groove of microchannel bottom surface is not closed, and after being bonded together, forms the complete pump housing with Micropump substrate; Be manufactured with trapezoidal protrusion at microchannel upper surface, each trapezoidal protrusion correspondence is positioned over the top of single-stage diffusion structure, and boundary dimension and the diffusing tube internal diameter of each trapezoidal protrusion match; Travelling wave drive array adopts the parallel distribution of piezoelectric bimorph, and one end of every sheet piezoelectric bimorph is placed in every grade of corresponding trapezoidal protrusion of diffusing tube, and the other end is fixed in Micropump substrate.

3. Micropump according to claim 2, the material of microchannel is PDMS, adopts thermal bonding method with the bonding method of Micropump substrate; In thermal bonding method, need the bonding region coating skim PDMS in Micropump substrate, the PDMS making microchannel adopts performed polymer and the curing agent proportioning of 10: 1, the PDMS that Micropump substrate covers to adopt performed polymer and the curing agent proportioning of 5: 1.

4. Micropump according to claim 2, the material of Micropump substrate and microchannel mould is PMMA or silicon, and processing method adopts plasma etching or miromaching.