Magnetic conduits in microfluidics

Patent metadata

Field	Value
Publication number	US-11148138-B2
Application number	US-201515756176-A
Country	US
Kind code	B2
Filing date	Sep 2, 2015
Priority date	Sep 2, 2015
Publication date	Oct 19, 2021
Grant date	Oct 19, 2021

Abstract

A digital microfluidics system with electrodes attached to a substrate and covered by a hydrophobic surface, and a control unit for manipulating liquid droplets by electrowetting; providing in close proximity to electrodes a magnetic conduit for directing a magnetic field of a backing magnet to the first hydrophobic surface; providing on the hydrophobic surface a liquid droplet that has magnetically responsive beads; moving by electrowetting the liquid droplet with the magnetically responsive beads until a part of which is placed atop of the magnetic conduit; actuating the backing magnet of the magnetic conduit and attracting/concentrating magnetically responsive beads; and while actuating the backing magnet, moving by electrowetting the liquid droplet with decreased number of magnetically responsive beads away from the specific magnetic conduit. Also disclosed are a method for suspending magnetically responsive beads in liquid portions or droplets in digital microfluidics and a disposable cartridge to carry out the methods.

First claim

What is claimed is:

1. A method of substantially removing magnetically responsive beads from liquid portions or droplets in digital microfluidics,
wherein the method comprises the steps of:
a) providing a digital microfluidics system ( 1 ) comprising a number or array of individual electrodes ( 2 ) attached to a first substrate ( 3 ), a first hydrophobic surface ( 5 ) located on said individual electrodes ( 2 ), and a central control unit ( 7 ) in operative contact with said individual electrodes ( 2 ) for controlling selection and for providing a number of said individual electrodes ( 2 ) with voltage for manipulating liquid portions ( 8 - 2 ) or liquid droplets ( 8 - 1 ) by electrowetting;
b) providing in the first substrate ( 3 ) of the microfluidics system ( 1 ) at least one magnetic conduit ( 9 ) comprising a backside and being configured to be backed by a backing magnet ( 10 ) with a magnetic field and being configured for directing said magnetic field through the magnetic conduit ( 9 ) to the first hydrophobic surface ( 5 ) on said individual electrodes ( 2 ), said at least one magnetic conduit ( 9 ) being located in close proximity to individual electrodes ( 2 );
c) providing on the hydrophobic surfaces ( 5 ) and above a path of selected electrodes ( 2 ′) at least one liquid portion ( 8 - 2 ) or liquid droplet ( 8 - 1 ) that comprises magnetically responsive beads ( 11 );
d) moving by electrowetting said at least one liquid portion ( 8 - 2 ) or liquid droplet ( 8 - 1 ) with the magnetically responsive beads ( 11 ) on said path of selected electrodes ( 2 ′) until at least a part of said at least one liquid portion ( 8 - 2 ) or liquid droplet ( 8 - 1 ) is placed atop of at least one specific magnetic conduit ( 9 );
e) actuating the backing magnet ( 10 ) so that it is operatively backing the at least one specific magnetic conduit ( 9 ), and thus attracting magnetically responsive beads ( 11 ) of said at least one liquid portion ( 8 - 2 ) or liquid droplet ( 8 - 1 ) through directing said magnetic field to the first hydrophobic surface ( 5 ) on said individual electrodes ( 2 ) by the at least one specific magnetic conduit ( 9 ) and concentrating attracted magnetically responsive beads ( 11 ); and
f) while actuating the backing magnet ( 10 ), moving by electrowetting said at least one liquid portion ( 8 - 2 )′ or liquid droplet ( 8 - 1 )′ with a substantially decreased number of magnetically responsive beads ( 11 ) on said path of selected electrodes ( 2 ) away from the specific magnetic conduit ( 9 ).

2. The method of claim 1 ,
wherein said at least one specific magnetic conduit ( 9 ) consists of a single solid ferromagnetic element, or of a multitude of randomly orientated ferromagnetic elements, or of an amorphous paste filled with ferromagnetic material.

3. The method of claim 1 ,
wherein said at least one specific magnetic conduit ( 9 ) is located under and is covered by an individual electrode ( 2 ).

4. The method of claim 1 ,
wherein said at least one specific magnetic conduit ( 9 ) is located beside of and is not covered by at least one individual electrode ( 2 ).

5. The method of claim 1 ,
wherein said backing magnet ( 10 ) is used to operatively back at least one specific magnetic conduit ( 9 ) and is configured as a permanent magnet ( 10 ′), or as a switchable permanent magnet ( 10 ″), or as an electromagnet ( 10 ′″).

6. The method of claim 1 ,
wherein actuating said backing magnet ( 10 ) is achieved by:
a) moving a permanent magnet ( 10 ′) to the backside of the at least one specific magnetic conduit ( 9 ); or
b) switching on a switchable permanent magnet ( 10 ″) that is located at the backside of the at least one specific magnetic conduit ( 9 ); or
c) energizing an electromagnet ( 10 ′″) that is located at the backside of the at least one specific magnetic conduit ( 9 ).

7. The method of claim 6 ,
wherein moving a permanent magnet ( 10 ′) is carried out by lifting, or swinging, or rotating the permanent magnet ( 10 ′) until its magnetic field is aligned with the at least one specific magnetic conduit ( 9 ).

8. The method of claim 6 ,
wherein switching on a switchable permanent magnet ( 10 ″) is carried out by turning a permanent magnet into an “ON” position of a magnetic base ( 29 ) or by switching off an electromagnet ( 33 ) that is compensating the magnetic field of a PE-magnet ( 32 ).

9. The method of claim 1 ,
wherein said at least one magnetic conduit ( 9 ) is located in neighboring notches ( 12 ) in-between of two of the individual electrodes ( 2 ) or located in a central void ( 13 ) of individual electrodes ( 2 ) that define this path of selected electrodes ( 2 ′).

10. The method of claim 1 ,
wherein said at least one magnetic conduit ( 9 ) is located in at least one notch ( 12 ) at one side, at opposite sides, or at a corner of individual electrodes ( 2 ) that define this path of selected electrodes ( 2 ′).

11. The method of claim 1 ,
wherein said at least one magnetic conduit ( 9 ) is located at a side of one narrowed individual electrode ( 2 ″) or in a space ( 14 ) between two narrowed individual electrodes ( 2 ″) that define this path of selected electrodes ( 2 ′).

12. The method of claim 1 ,
wherein said at least one magnetic conduit ( 9 ) is a cylindrical, cuboid magnetic conduit ( 9 ′) located in a blind hole ( 15 ) or in a through hole ( 16 ) in the first substrate ( 3 ) of the digital microfluidics system ( 1 ).

13. The method of claim 1 ,
wherein said at least one magnetic conduit ( 9 ) is a conical, pyramidal magnetic conduit ( 9 ″) located in a blind hole ( 15 ) in the first substrate ( 3 ) of the digital microfluidics system ( 1 ).

14. The method of claim 1 ,
wherein a disposable cartridge ( 17 ) is provided which is accommodated on a cartridge accommodation site ( 18 ) of the digital microfluidics system ( 1 ), the
disposable cartridge ( 17 ) comprising the first hydrophobic surface ( 5 ) that belongs to a working film ( 19 ) and a second hydrophobic surface ( 6 ) that belongs to a cover plate ( 20 ) of the disposable cartridge ( 17 ), a working gap ( 4 ) being located in-between the two hydrophobic surfaces ( 5 , 6 ) of the disposable cartridge ( 17 ).

15. The method of claim 14 ,
wherein the working film ( 19 ) of the disposable cartridge ( 17 ) comprises a backside ( 21 ) that, when the disposable cartridge ( 17 ) is accommodated on a cartridge accommodation site ( 18 ) of the digital microfluidics system ( 1 ), touches an uppermost surface ( 22 ) of the cartridge accommodation site ( 18 ) of the digital microfluidics system ( 1 ).

16. The method of claim 14 ,
wherein the cover plate ( 20 ) of the disposable cartridge ( 17 ) is configured as a rigid cover plate or as a flexible cover plate.

17. The method of claim 15 ,
wherein the cover plate ( 20 ) of the disposable cartridge ( 17 ) is configured as a rigid cover plate,
and wherein the working film ( 19 ) of the disposable cartridge ( 17 ) is configured as a flexible sheet that spreads on the uppermost surface ( 22 ) of the cartridge accommodation site ( 18 ) of the digital microfluidics system ( 1 ), the digital microfluidics system ( 1 ) comprising a vacuum source ( 23 ) for establishing an underpressure in an evacuation space ( 24 ) between the uppermost surface ( 22 ) of the cartridge accommodation site ( 18 ) and the backside ( 21 ) of the working film ( 19 ) of the disposable cartridge ( 17 ).

18. The method of claim 17 ,
wherein the cartridge accommodation site ( 18 ) of the digital microfluidics system ( 1 ) or th

Assignees

• Tecan Trading Ag
• Perroud Thomas
• Tran Dan
• Hoffmeyer Daniel
• Lay Tiffany
• Dhindsa Manjeet

Inventors

• Perroud Thomas
• Tran Dan
• Hoffmeyer Daniel
• Lay Tiffany
• Dhindsa Manjeet

Classifications

• C02F1/484

  using electromagnets · CPC title

• B01L2400/043

  magnetic forces · CPC title

• B01L2400/0427

  Electrowetting · CPC title

• B01L2300/123

  Flexible; Elastomeric · CPC title

• B01L2300/0816

  Cards, e.g. flat sample carriers usually with flow in two horizontal directions · CPC title