WO2021225597A1

WO2021225597A1 - Particle separator molded microfluidic substrate

Info

Publication number: WO2021225597A1
Application number: PCT/US2020/032000
Authority: WO
Inventors: Chien-Ha CHEN; Viktor Shkolnikov; Michael G. Groh
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2020-05-08
Filing date: 2020-05-08
Publication date: 2021-11-11

Abstract

A molded microfluidic substrate of a particle separator includes a molding compound layer and focusing microfluidic channels and separation microfluidic channels within the molding compound layer. The focusing microfluidic channels form a sample channel and sheath channels of a hydrodynamic particle focusing region of the particle separator. The separation microfluidic channels are fluidically connected to the focusing microfluidic channels, and form a preseparation channel and post-separation channels of a dielectrophoresis separation region of the particle separator.

Description

PARTICLE SEPARATOR MOLDED MICROFLUIDIC SUBSTRATE

BACKGROUND

[0001] Diagnostic tools can be employed to detect the presence of cancerous as well as other types of cells. For the highest likelihood of successful recovery, early detection is paramount but conversely most difficult to achieve. For example, within a given blood sample, the ratio of malignant to non- malignant cells may be exceedingly low. Many diagnostic tools may be unable to detect the presence of malignant cells until their numbers have increased to undesirably high levels. BRIEF DESCRIPTION OF THE DRAWINGS

[0002] FIGs. 1 and 2 are diagrams of an example particle separator having a molded microfluidic substrate.

[0003] FIGs. 3A and 3B are diagrams of different example focusing regions of a molded microfluidic substrate of a particle separator. [0004] FIG. 4 is a flowchart of an example method for manufacturing a particle separator having a molded microfluidic substrate.

[0005] FIG. 5 is a flowchart of an example method for manufacturing a molded microfluidic substrate of a particle separator.

[0006] FIGs. 6A, 6B, 6C, 6D, 6E, 6F, 6G, and 6H are cross-sectional diagrams depicting example performance of the method of FIG. 5 using a molded interconnect substrate (MIS) technique. [0007] FIGs. 7A, 7B, and 7C are cross-sectional diagrams depicting example performance of the method of FIG. 5 using a wire bonding technique. [0008] FIG. 8 is a block diagram of an example molded microfluidic substrate of a particle separator. [0009] FIG. 9 is a block diagram of an example particle separator having a molded microfluidic separator.

DETAILED DESCRIPTION

[0010] As noted within the background, diagnostic tools can be employed to detect the presence of certain types of cells within a sample. One type of such a diagnostic tool is known as a particle, or cell, separator. A particle separator can physically separate cells of interest from other cells within a sample, even if the number of the cells of interest are exceedingly rare within the sample. Therefore, a particle separator may also be referred to as a rare cell isolator. [0011] Particle separators, however, can be relatively expensive and difficult to manufacture. A particle separator can have a microfluidic substrate with various microfluidic channels at micron-layer widths, such as in the hundreds or tens of microns or even smaller. Such particle separator microfluidic substrates are often made using semiconductor fabrication techniques to achieve the desired miniaturization. Forming microfluidic substrates on silicon wafers, however, is difficult, and does not lend itself to relatively low-cost separators, even if economies of scale are realized.

[0012] Described herein are techniques for fabricating a microfluidic substrate of a particle separator in a molded manner. Specifically, the molded microfluidic substrate can be formed using techniques that may otherwise be employed to fabricate a molded interconnect substrate (MIS) during semiconductor packaging. However, the metal interconnects are instead sacrificial and etched away to form the microfluidic channels of the molded microfluidic substrate.

[0013] In another implementation, the sacrificial metal can be formed using wire bonding techniques that may otherwise be employed during semiconductor packaging, instead of using a MIS technique. The metal bond wires are similarly encapsulated in molding compound before being etched away to form the microfluidic channels. A particle separator having a molded microfluidic substrate formed as described herein can be made more cost effectively, and indeed can more easily provide for channel topologies that semiconductor fabrication techniques may be able to realize with great difficulty if at all.

[0014] FIGs. 1 and 2 show an example particle separator 100. The particle separator 100 includes a molded microfluidic substrate 102, electrodes 104A, 104B, and 104C that are collectively referred to as the electrodes 104, and a transparent lid 105. The particle separator 100 can be the particle separator described in the PCT patent application entitled “particle separation,” filed on April 23, 2017, and assigned international application number PCT/US2017/029028, but with a molded microfluidic substrate 102 formed in accordance with the techniques described herein.

[0015] The molded microfluidic substrate 102 can be fabricated from a molding compound, such as epoxy molding compound (EMC) like Ajinomoto buildup film (ABF) available from Ajinomoto Co., Inc., of Tokyo, Japan. The molding compound may be an inherently electrically insulating molding material. By comparison, a microfluidic substrate formed within a silicon die can be electrically conductive, which may necessitate coating the formed microfluidic channels with a passivation layer to avoid electrical interaction between the cells and the silicon.

[0016] The molding material may be impregnated with thermally conductive particles to increase the thermal conductivity of the molded microfluidic substrate 102. Thermal conductivity permits built-up heat within the microfluidic substrate 102 to convectively dissipate, and which may otherwise affect the operation of the particle separator 100. The particles can include silica particles, silicon nitride particles, alumina particles, and/or aluminum nitride particles, at concentrations sufficient to impart thermal conductivity while not affecting the electrical insulating nature of the molding material. [0017] The molded microfluidic substrate 102 includes a hydrodynamic particle focusing region 106 and dielectrophoresis separation regions 108 and 110 of the particle separator 100 in the example of FIGs. 1 and 2. The focusing region 106 hydrodynamically sandwiches sample cells in a column between columns of buffer or sheath cells. That is, the focusing region 106 aligns fluid- entrained sample particles between sheet flows of buffer or sheath solutions. [0018] Each dielectrophoresis separation region 108 and 110 separates cells of interest using dielectrophoretic forces exerted by electrical fields that the electrodes 104 generate. For instance, the dielectrophoresis separation region 108 may dielectrophoretically separate cells of interest from other sample cells. The dielectrophoresis separation region 110 may then further dielectrophoretically separate cells of interest of one type from cells of interest of another type. [0019] The molded microfluidic substrate 102 includes fluidic inlets 112A,

112B, 112C, which are collectively referred to as the fluidic inlets 112. The fluidic inlets 112 permit fluids to enter the particle separator 100 at the bottom of the microfluidic substrate 102. For example, a fluidic sample including cells of interest, such as malignant cells of different types, as well as other sample cells, such as benign cells, may be introduced at the inlet 112A. The same or different buffer or sheath solutions made up of buffer or sheath cells may be introduced at the inlets 112B and 112C.

[0020] The molded microfluidic substrate 102 includes fluidic outlets 114A, 114B, and 114C, which are collectively referred to as the fluidic outlets 114. The fluidic outlets 114 permit fluids to exit the particle separator 100 at the bottom of the substrate 102. For example, sample cells other than the sample cells of interest may exit at the outlet 114A, along with buffer or sheath cells. Different types of sample cells of interest may respectively exit at the outlets 114B and 114C, also along with buffer or sheath cells. [0021] The electrode 104A may be a ground electrode, whereas the electrodes 104B and 104C may respectively be positive and negative electrodes at which positive and negative voltages are applied. An alternating current at a specified frequency may be applied between the electrodes 104B and 104C. The resultant electric fields exert dielectric forces in a plane on the particles within the dielectrophoresis separation regions 108 and 110 to dielectrophoretically separate the particles. The transparent lid 105, which may be glass, permits visual inspection of particle separation as it occurs. [0022] As shown specifically in FIG. 2, the molded microfluidic substrate

102 includes focusing microfluidic channels 202A, 202B, and 202C, collectively referred to as the channels 202, and a focusing microfluidic channel 204, which define the hydrodynamic particle focusing region 106 of the particle separator 100. The channel 202A is a central microfluidic channel forming a sample channel of the focusing region 106. The channels 202B and 202C are side microfluidic channels planarly parallel to with the central microfluidic channel 202A at either side of the channel 202A and form respective side sheath channels of the region 106. The channel 204 is a microfluidic channel forming a collector channel of the focusing region 106, into which the channels 202 empty. [0023] Also shown specifically in FIG. 2, the molded microfluidic substrate

102 includes separation microfluidic channels 206, 208A, and 208B, the latter two of which are collectively referred to as the channels 208, and all of which define the dielectrophoresis separation region 108 of the particle separator 100. The channel 206 is a trunk microfluidic channel fluidically adjacent to the microfluidic channel 204 of the hydrodynamic particle focusing region 106 and forming a pre-separation channel of the separation region 108. The channels 208 fluidically branch from the trunk microfluidic channel 204 and form post separation channels of the separation region 108. [0024] As shown in FIG. 2, the molded microfluidic substrate 102 includes microfluidic inlet channels 212A, 212B, and 212C, collectively referred to as the inlet channels 212. The microfluidic inlet channels 212A, 212B, and 212C are respectively fluidically connected to the fluidic inlets 112A, 112B, and 112C. The microfluidic inlet channels 212A, 212B, and 212C are further respectively fluidically connected to the focusing microfluidic channels 202A, 202B, and 202C of the focusing region 106.

[0025] As also shown in FIG. 2, the molded microfluidic substrate 102 includes microfluidic outlet channels 210A, 210B, and 212C, collectively referred to as the outlet channels 210, and which are respectively fluidically connected to the fluidic outlets 114A, 114B, and 114C. The outlet channel 210A is also fluidically connected to the post-separation channel 208A of the separation region 108. The outlet channels 210B and 210C form post-separation channels of the separation region 110, whereas the post-separation channel 208B of the separation region 108 forms the pre-separation channel of the separation region 110.

[0026] In operation of the particle separator 102, the focusing microfluidic channel 202A of the focusing region 106 planarly aligns the sample cells within a column. The focusing microfluidic channels 202B and 202C of the focusing region 106 similarly planarly align buffer or sheath cells within respective columns. The sample cells remain so hydrodynamically focused as they exit the focusing microfluidic channels 202 and enter the focusing microfluidic channel 204. [0027] The electrodes 104 impart an electric field across the separation microfluidic channels 206 and 208 of the particle separation region 108. The electric field dielectrophoretically diverts the sample cells of interest (along with some buffer or sheath cells) from the pre-separation microfluidic channel 206 to the post-separation microfluidic channel 208B. The electric field similarly dielectrophoretically diverts the other sample cells (along with some other buffer or sheath cells) from the pre-separation microfluidic channel 206 to the post separation microfluidic channel 208A.

[0028] The electrodes 104B and 104C similarly impart an electric field across the separation particle separation region 110. The electric field dielectrophoretically diverts the sample cells of interest of a first type (along with some buffer or sheath cells) from the microfluidic channel 208B to the microfluidic channel 210C. The electric field dielectrophoretically diverts the sample cells of interest of a second type (along with some other buffer or sheath cells) from the microfluidic channel 208B to the microfluidic channel 210B.

[0029] FIG. 3A shows an example of the hydrodynamic focusing region 106 in detail. The focusing region 106 includes the focusing microfluidic channels 202 and 204, with the latter channel 204 depicted in dotted manner for illustrative clarity. The central microfluidic channel 202A is disposed between the side microfluidic channels 202B and 202C. Specifically, the side channel 202B is planarly parallel to the central channel 202A at one side of the central channel 202A, and the side channel 202B is planarly parallel to the central channel 202A at an opposite side of the central channel 202A. [0030] FIG. 3B shows another example of the hydrodynamic focusing region 106 in detail. Beside the focusing microfluidic channels 202 and 204, where the latter channel 204 is depicted in dotted manner for illustrative clarity, the focusing region 106 also includes the focusing microfluidic channels 302A and 302B, which are collectively referred to as the microfluidic channels 302.

The central microfluidic channel 202A is again disposed between the side microfluidic channels 202B and 202C, which are planarly parallel to the central channel 202A at opposing sides of the channel 202A.

[0031] The focusing microfluidic channel 302A is a top side channel planarly parallel to and above the central microfluidic channel 202A at a top side of the central channel 202A. The focusing microfluidic channel 302B is similarly a bottom side channel planarly parallel to and below the central microfluidic channel 202A at a bottom side of the central channel 202A. The focusing microfluidic channels 302A and 302B respectively form top side and bottom side sheath channels of the hydrodynamic focusing region 106.

[0032] The central microfluidic channel 202A is therefore surrounded by side microfluidic channels 202B, 202C, 302A, and 302B in the example of FIG. 3B, as opposed to being disposed between two side channels 202 in FIG. 3A. The more complex channel topology of FIG. 3B can provide for improved hydrodynamic focusing of the sample cells as compared to FIG. 3A. The channel topology of FIG. 3B is difficult if not impossible to fabricate within a semiconductor die, but is more easily achieved at little extra cost within a molded substrate according to the techniques described herein. [0033] FIG. 4 shows an example method 400 for manufacturing a particle separator having a molded microfluidic substrate. The particle separator may be the described particle separator 100 having the molded microfluidic substrate 102. The method 400 includes fabricating the molded microfluidic substrate of the particle separator (402). The molded microfluidic substrate can be formed using techniques that may otherwise be employed to fabricated a MIS during semiconductor packaging, or using wire bonding techniques also may otherwise be used during semiconductor packaging.

[0034] For example, the molded microfluidic substrate of the particle separator may be formed using the MIS-related techniques described in the PCT patent application entitled “molded structures with channels,” filed on June 25, 2019, and assigned international application number PCT/US2019/39074. As another example, the molded microfluidic substrate may be formed using the wire bonding-related techniques described in the PCT patent application entitled, “molded microfluidic substrate having microfluidic channel corresponding to sacrificial metal bond wire,” filed on April 10, 2020, and assigned international application number PCT/US2020/27597.

[0035] The method 400 includes forming electrodes, such as the described electrodes 104, on the molded microfluidic substrate of the particle separator (404), adjacent to separation microfluidic channels of the substrate.

For example, the electrodes may be formed by conductive metal deposition or plating. The method 400 includes attaching a lid, such as the described lid 105, above the microfluidic substrate and the electrodes (406). The lid may be a transparent glass lid that is adhesively attached.

[0036] FIG. 5 shows an example method 500 for manufacturing the molded microfluidic substrate of a particle separator. The molded microfluidic substrate may be the described molded microfluidic substrate 102 of the particle separator 100. The method 500 is consistent with the MIS-related techniques of the PCT patent application assigned international application number PCT/US2019/39074 and with the wire bonding-related techniques of the PCT patent application assigned international application number PCT/US2020/27597 that have been referenced above.

[0037] The method 500 includes forming sacrificial metal traces on a support layer in correspondence with focusing microfluidic channels of a hydrodynamic particle focusing region and with separation microfluidic channels of a dielectrophoresis separation region (502). The sacrificial metal traces can be formed in correspondence with other channels as well. Molding compound may make up the support layer. In the case in which wire bonding-related techniques are employed, the sacrificial metal traces may be in the form of round metal bond wire or rectangular, including square, metal ribbon.

[0038] The method 500 includes applying molding compound on the support layer (504). Molding compound application encapsulates the sacrificial metal traces within a molding compound layer that includes the support layer of the same molding compound and which corresponds to the molded microfluidic substrate being formed. Per arrow 503, the method 500 may be repeated at part 502 one time or multiple times in one implementation, such as in the case when an MIS technique is used, as described later in the detailed description. The method 500 includes then etching away the sacrificial metal traces (506), forming the microfluidic channels within the molding compound layer and yielding the molded microfluidic substrate of the particle separator.

[0039] FIGs. 6A-6H illustratively depict example performance of the method 500 to fabricate a molded microfluidic substrate of a particle separator. Fabrication of focusing microfluidic channels of the microfluidic substrate is specifically shown in FIGs. 6A-6FI. Furthermore, the fabricated focusing microfluidic channels include four sheath channels in particular. Therefore,

FIGs. 6A-6FI illustrate example performance of the method 500 to fabricate a microfluidic substrate having a focusing region such as that of FIG. 3B.

[0040] FIGs. 6A-6FI specifically illustrate example performance of the method 500 when the microfluidic substrate is fabricated using MIS-related techniques, like that of the referenced PCT patent application assigned international application number PCT/US2019/39074. In FIG. 6A, a layer 602 of plating resist can be formed on a support layer 600 of molding compound. The plating resist layer 602 has a thickness corresponding to a thickness of a desired bottom side sheath microfluidic channel. A region 603 within the layer 602 is photolithographically defined in correspondence with a width of the desired bottom side sheath microfluidic channel and then cured.

[0041] In FIG. 6B, the photolithographically defined and cured region 603 of the plating resist layer 602 of FIG. 6A is developed, resulting in a cavity 605 within the layer 602 on the support layer 600 of molding compound. The cavity 605 corresponds to the desired bottom side sheath microfluidic channel. In FIG. 6C, the cavity 605 of FIG. 6B is plated to form a sacrificial metal trace 604A on the support layer 600, in correspondence with a desired bottom side sheath microfluidic channel. The metal trace 604A may be copper or aluminum, or another type of metal.

[0042] In FIG. 6D, the remaining plating resist layer 602 of FIG. 6B is stripped, such as by using a solvent or alkaline-based stripping solution, leaving just the sacrificial metal trace 604A on the support layer 600. In FIG. 6E, a layer 610 of the same molding compound as the support layer 600 is applied to the layer 600, encapsulating the sacrificial metal trace 604A. The molding compound layer 603 is ground to a thickness above the top surface of the metal trace 604A in correspondence with a desired distance separating the bottom side sheath microfluidic channel to which the trace 604A corresponds and the desired sample and (left and right) side sheath microfluidic channels.

[0043] The process that has been described with reference to FIGs. 6A-6D is repeated to form sacrificial metal traces corresponding to desired sample and (left and right) side sheath microfluidic channels. As such, in FIG. 6F, sacrificial metal traces 614A, 614B, and 614C of the same metal as the metal trace 604A and which are collectively referred to as the sacrificial metal traces 614 are formed on the layer 610 in correspondence with the desired sample and (left and right) side sheath microfluidic channels. A layer 620 of the same molding compound as the layers 600 and 610 is applied to the layer 610 to encapsulate the metal traces 614, and is then ground in correspondence with a desired distance separating the sample and (left and right) side sheath microfluidic channels and the desired top side sheath microfluidic channel.

[0044] The described process is repeated again to form a sacrificial metal trace corresponding to the desired top side sheath microfluidic channel. As such, in FIG. 6G, a sacrificial metal trace 604B of the same metal as the metal traces 604A and 614 is formed on the layer 620, in correspondence with the desired top side sheath microfluidic channel. The sacrificial metal traces 604A and 604B are collectively referred to as the metal traces 604. A layer 630 of the same molding compound as the layers 600, 610, and 620 is applied to the layer 620 to encapsulate the metal trace 604B, and is then ground to expose the sacrificial metal trace 604 B.

[0045] In FIG. 6H, the sacrificial metal traces 604 and 614 are etched away. The removal of the metal traces 604 and 614 forms the focusing microfluidic channels 202 and 302 of FIG. 3B, encapsulated within a molding compound layer 640 that encompasses the layers 600, 610, 620, and 630 of FIG. 6F. Metal trace removal thus yields the particle separator molded microfluidic substrate 106 of FIG. 3B.

[0046] FIGs. 7A, 7B, and 7C also illustratively depict example performance of the method 500 of FIG. 5 to fabricate a molded microfluidic substrate of a particle separator. As in FIGs. 6A-6FI, fabrication of focusing microfluidic channels of the microfluidic substrate is specifically shown in FIGs. 7A-7C. The fabricated focusing microfluidic channels include four sheath channels in particular. FIGs. 7A-7C illustrate example performance of the method 500 to fabricate a microfluidic substrate having a focusing region such as that of FIG. 3B. [0047] FIGs. 7A-7C specifically illustrate example performance of the method 500 when the microfluidic substrate is fabricated using wire bonding- related techniques, like that of the referenced PCT patent application assigned international application number PCT/US2020/27597. In FIG. 7A, the sacrificial metal traces 604 and 614 that have been described are formed by bending bond wire or ribbon in correspondence with desired focusing microfluidic channels.

The bond wire or ribbon corresponding to each metal trace 604 or 614 can be attached to the support layer 600 or to the bond wire or ribbon corresponding to a different trace 604 or 614. In the case of bond ribbon, the metal traces 604 and 614 may be rectangular as depicted, and in the case of bond wire may be round. [0048] In FIG. 7B, a layer 730 of the same molding compound as the support layer 600 is applied to the layer 600, encapsulating the sacrificial metal traces 604 and 614. In FIG. 7C, the molding compound layer 630 is ground to expose the sacrificial metal trace 604B. The metal traces 604 and 614 are etched away as has been described above with respect to FIG. 6H, where the molding compound layer 640 of FIG. 6H encompasses the layers 600 and 730 of FIG. 7C. Such metal trace removal thus again yields the particle separator molded microfluidic substrate 160 of FIG. 3C.

[0049] FIG. 8 shows a block diagram of an example molded microfluidic substrate 102 of a particle separator. The molded substrate 102 includes a molding compound layer 640 defining a hydrodynamic particle focusing region 106 and a dielectrophoresis separation region 108 of the particle separator. The focusing region 106 includes focusing microfluidic channels 802 that form a sample channel 804 and sheath channels 806. The separation region 108 includes separation microfluidic channels 808 fluidically connected to the focusing channels 802 and that form a pre-separation channel 810 and post separation channels 812.

[0050] FIG. 9 shows a block diagram of an example particle separator 100 including a molded microfluidic substrate 102 and electrodes 104. The molded microfluidic substrate 102 is of a molding compound and defines a hydrodynamic particle focusing region 106 and a dielectrophoresis separation region 108. The focusing region 106 includes focusing microfluidic channels 802, whereas the separation region 108 includes separation microfluidic channels 808 that are adjacent to the focusing microfluidic channels as well as to the electrodes 104. [0051] Techniques have been described herein for fabricating a particle separator having a molded microfluidic substrate. The microfluidic substrate can specifically be fabricated using MIS-related techniques or wire bonding-related techniques that may otherwise be employed during semiconductor packaging. Such techniques permit more complex microfluidic channel topologies to be more easily formed at little additional expense.

Claims

We claim:

1. A molded microfluidic substrate of a particle separator, comprising: a molding compound layer; a plurality of focusing microfluidic channels within the molding compound layer and forming a sample channel and a plurality of sheath channels of a hydrodynamic particle focusing region of the particle separator; and a plurality of separation microfluidic channels within the molding compound layer, fluidically connected to the focusing microfluidic channels, and forming a pre-separation channel and a plurality of post-separation channels of a dielectrophoresis separation region of the particle separator.

2. The molded microfluidic substrate of claim 1 , wherein the focusing microfluidic channels comprise: a central microfluidic channel forming the sample channel of the hydrodynamic particle focusing region of the particle separator; a first side microfluidic channel planarly parallel to the central microfluidic channel at a first side of the central microfluidic channel and forming a first side sheath channel of the hydrodynamic particle focusing region; a second side microfluidic channel planarly parallel to the central microfluidic channel at a second side of the central microfluidic channel and forming a second side sheath channel of the hydrodynamic particle focusing region; and a microfluidic channel into which the central microfluidic channel and the first and second microfluidic channels fluidically empty.

3. The molded microfluidic substrate of claim 2, wherein the focusing microfluidic channels further comprise: a top side microfluidic channel parallel to and above the central microfluidic channel at a top side of the central microfluidic channel and forming a top side sheath channel of the hydrodynamic particle focusing region; and a bottom side microfluidic channel parallel to and below the central microfluidic channel at a bottom side of the central microfluidic channel and forming a bottom side sheath channel of the hydrodynamic particle focusing region, wherein the top and bottom side microfluidic channels further fluidically empty into the central microfluidic channel.

4. The molded microfluidic substrate of claim 1 , wherein the separation microfluidic channels comprise: a trunk microfluidic channel fluidically adjacent to the focusing microfluidic channels and forming the pre-separation channel of the dielectrophoresis separation region of the particle separator; and first and second branch microfluidic channels fluidically branching from the focusing microfluidic channel and forming first and second post-separation channels of the dielectrophoresis separation region.

5. The molded microfluidic substrate of claim 1 , wherein the molding compound layer comprises a layer of an inherently insulating molding material.

6. The molded microfluidic substrate of claim 5, wherein the inherent insulating molding material is impregnated with a plurality of thermally conductive particles to increase thermal conductivity of the molding compound layer.

7. The molded microfluidic substrate of claim 6, wherein the thermally conductive particles are selected from: silica particles, silicon nitride particles, alumina particles, and aluminum nitride particles.

8. A particle separator comprising: a molded microfluidic substrate of a molding compound having a plurality of focusing microfluidic channels forming a hydrodynamic particle focusing region, and having a plurality of separation microfluidic channels adjacent to the focusing microfluidic channels and forming a dielectrophoresis separation region; and a plurality of electrodes on the molded microfluidic substrate adjacent to the separation microfluidic channels.

9. The particle separator of claim 8, wherein the focusing microfluidic channels forming the hydrodynamic particle focusing region comprise: a sample microfluidic channel; and a plurality of sheath channels parallel to and surrounding the sample microfluidic channel.

10. The particle separator of claim 9, wherein the separation microfluidic channels of the dielectrophoresis separation region comprise: a pre-separation microfluidic channel fluidically adjacent to the focusing microfluidic channels; and a plurality of post-separation microfluidic channels fluidically branching from the focusing microfluidic channel.

11. The particle separator of claim 8, wherein the molded microfluidic substrate further has: a plurality of fluidic inlets; a plurality of fluidic outlets; a plurality of microfluidic inlet channels fluidically adjacent to the focusing microfluidic channels and the fluidic inlets; and a plurality of microfluidic outlet channels fluidically adjacent to the separation microfluidic channels and the fluidic outlets.

12. The particle separator of claim 11 , further comprising: a transparent lid above the molded microfluidic substrate and the electrodes.

13. A method comprising: forming a plurality of sacrificial metal traces on a support layer in correspondence with a plurality of focusing microfluidic channels of a hydrodynamic particle focusing region of a particle separator and a plurality of separation microfluidic channels of a dielectrophoresis separation region of the particle separator; applying a molding compound on the support layer, encapsulating the sacrificial metal traces within a molding compound layer corresponding to a molded microfluidic substrate of the particle separator defining the hydrodynamic particle focusing and dielectrophoresis separation regions; and etching away the sacrificial metal traces from the molding compound layer, forming the focusing microfluidic channels and the separation microfluidic channels within the molding compound layer and yielding the molded microfluidic substrate of the particle separator.

14. The method of claim 13, wherein the sacrificial metal structures are formed three dimensionally in correspondence with the focusing microfluidic channels comprising: a sample microfluidic channel; and a plurality of sheath channels parallel to and surrounding the sample microfluidic channel.

15. The method of claim 13, further comprising: forming a plurality of electrodes on the molded microfluidic substrate adjacent to the separation microfluidic channels; and attaching a lid above the molded microfluidic substrate and the electrodes, yielding the particle separator including the molded microfluidic substrate, the electrodes, and the lid.