Impedance based devices and methods for use in assays
A device for detecting cells and/or molecules on an electrode surface is disclosed. The device detects cells and/or molecules through measurement of impedance changes resulting from the cells and/or molecules. A disclosed embodiment of the device includes a substrate having two opposing ends along a longitudinal axis. A plurality of electrode arrays are positioned on the substrate. Each electrode array includes at least two electrodes, and each electrode is separated from at least one adjacent electrode in the electrode array by an expanse of non-conductive material. The electrode has a width at its widest point of more than about 1.5 and less than about 10 times the width of the expanse of non-conductive material. The device also includes electrically conductive traces extending substantially longitudinally to one of the two opposing ends of the substrate without intersecting another trace. Each trace is in electrical communication with at least one of the electrode arrays.
1. A method of making a device for detecting cells on an electrode surface through measurement of impedance change resulting from attachment of cells on the electrode surface, comprising:
a) providing a non-conductive substrate with a deposited electrically conductive metal film;
b) patterning said electrically conductive metal film using laser ablation of said conductive film from said substrate to form an array of electrodes, wherein each electrode comprises at least two electrode structures having a thickness up to 230 nm and that permit impedance measurement at each electrode structure, wherein each electrode structure comprises a plurality of electrode elements; and
c) cleaning said substrate with an acid or base solution to remove re-deposition of ablated conductive material;
d) connecting said electrode structures to a surface of said substrate opposite said electrode structures with a means for electronic connection selected from the group consisting of a flex circuit, metal clips, electrically conductive lines formed through said substrate, electrical wires and electrically conductive paste filled holes; and
e) assembling said substrate to a bottomless multi-well plate to form an electrode-containing multi-well plate; wherein said electrode structures are positioned within wells of said multi-well plate.
2. The method according to claim 1 , wherein said non-conductive substrate is constructed from a material selected from the group consisting of glass, a polymer, a plastic, a ceramic, fiberglass, and a combination thereof.
3. The method according to claim 1 , wherein said electrically conductive metal film is constructed from a material selected from the group consisting of gold, chromium, nickel, copper, platinum, aluminum, sliver, steel, indium-tin-xide, and a combination thereof.
4. The method according to claim 1 , wherein said electronic connection means comprises a PCB board with downward-facing straight-line conductor lines, wherein one end of said conductor lines is conductively bonded to connection pads on said substrate and the other end can be accessed from the bottom.
5. The method according to claim 1 , wherein said electronic connection means comprises a flex circuit wrapped around edges of said substrate, wherein one end of said flex circuit comprises metal wires conductively bonded to connection pads on said substrate.
6. The methods according to claim 1 , wherein said electronic connection means comprises metal clips that connect electrode pads on the top side of said substrate to the bottom side of said substrate.
7. The method according to claim 1 , wherein said electronic connection means comprises wire bonding that connects connection pads located on said substrate to a PCB board comprising conductive vias, wherein said PCB board is accessible from the bottom side.
8. The method according to claim 1 , wherein said electronic connection means comprises conductive-pasted-filled holes, further wherein the step of connecting said electrode structures further comprises producing holes at determined locations of said substrate and filling said holes with conductive paste.
9. The method according to claim 1 , wherein the cleaning step further comprises mechanical scrubbing of the substrate.
10. The method according to claim 1 , wherein said multi-well plate is selected from the group consisting of a 3 well, 12 well, 24 well, 48 well, 96 well, 192 well, 384 well, 768 well and 1536 well plate.
11. The method according to claim 1 , wherein said electrode structures with electrode elements comprising com rise a geometry selected from the group consisting of circle-on-line, diamond-on-line, and castellated.
12. The method according to claim 1 , wherein the widths of said electrode elements are from 20 microns to 500 microns.
13. The method according to claim 1 , wherein a gap between electrode elements of different electrode structures is between about 3 microns and about 80 microns.
14. The method according to claim 1 , wherein said electrode structures with electrode elements comprise an interdigitated geometry or sinusoidal geometry.