Wireless swnt sensor integrated with microfluidic system for various liquid sensing applications

Patent metadata

Field	Value
Publication number	US-2016129455-A1
Application number	US-201514974517-A
Country	US
Kind code	A1
Filing date	Dec 18, 2015
Priority date	Jan 10, 2012
Publication date	May 12, 2016
Grant date	—

Abstract

Sensors based on single-walled carbon nanotubes (SWNT) are integrated into a microfluidic system outfitted with data processing and wireless transmission capability. The sensors combine the sensitivity, specificity, and miniature size of SWNT-based nanosensors with the flexible fluid handling power of microfluidic “lab on a chip” analytical systems. Methods of integrating the SWNT-based sensor into a microfluidic system are compatible with the delicate nature of the SWNT sensor elements. The sensor devices are capable of continuously and autonomously monitoring and analyzing liquid samples in remote locations, and are applicable to real time water quality monitoring and monitoring of fluids in living systems and environments. The sensor devices and fabrication methods of the invention constitute a platform technology, because the devices can be designed to specifically detect a large number of distinct chemical agents based on the functionalization of the SWNT. The sensors can be combined into a multiplex format that detects desired combinations of chemical agents simultaneously.

First claim

What is claimed is:

1 . A method of fabricating a sensor device for the detection of a chemical agent in a liquid sample, the method comprising the steps of:
(a) depositing a conductive layer onto an insulating or semiconducting substrate, whereby the conductive layer forms a pattern comprising first and second microelectrodes and having a gap between the first and second microelectrodes; (b) depositing an aqueous suspension of SWNT onto the substrate so as to cover the gap between the first and second microelectrodes with the aqueous suspension; (c) applying an AC voltage between the first and second microelectrodes, whereby SWNT are dielectrophoretically assembled across the gap and form an electrical connection at one end of the SWNT with the first microelectrode and at another end of the SWNT with the second microelectrode; (d) removing said aqueous suspension of SWNT from the substrate; (e) forming a parylene shadow mask covering the assembled SWNT; (f) plasma treating the surface of the substrate having the assembled SWNT; (g) removing the shadow mask; and (h) bonding a microfluidic channel to the substrate such that it encloses the gap and the assembled SWNT, and is fluidically connected on one side of the gap to an inlet port and on another side of the gap to an outlet port.

2 . The method of claim 1 , wherein step (f) comprises forming a microfluidic channel in PDMS using SU-8 replica molding and photolithography and exposing the microfluidic channel and the substrate to an oxygen plasma for about 30 seconds; and wherein step (h) comprises heat bonding the microfluidic channel to the substrate at about 150° C. for about 15 minutes.

3 . The method of claim 1 , wherein a plurality of first and second microelectrode pairs is formed in step (a), each pair having a gap between the microelectrodes of the pair, and wherein in step (c) SWNT are dielectrophoretically assembled across each gap and form an electrical connection at one end of the SWNT with the first microelectrode of each pair and at another end of the SWNT with the second microelectrode of each pair.

4 . The method of claim 1 , wherein in step (g) the shadow mask is removed mechanically.

5 . The method of claim 3 , wherein steps (b) through (d) are repeated for one or more cycles of SWNT assembly; wherein at each performance of step (c) the voltage is applied between a different pair of microelectrodes; wherein for each performance of steps (b) and (c) the SWNT are differently functionalized, whereby a multiplex sensor is fabricated.

6 . The method of claim 1 , further comprising:
(i) attaching to the substrate a detection circuit connected to said first and second microelectrodes and capable of detecting a change in an electrical property of the SWNT.

7 . The method of claim 6 , further comprising:
(j) attaching to the substrate a wireless transmitter capable of transmitting an output signal from said detection circuit to a remote receiver.

8 . The method of claim 6 , further comprising:
(j) attaching to the substrate a data processing module capable of processing an output signal from said detection circuit and outputting a signal that provides information on the presence and/or amount of said chemical agent.

9 . The method of claim 8 , further comprising:
(k) attaching to the substrate a wireless transmitter capable of transmitting an output signal from said data processing module to a remote receiver.

10 . A method of fabricating a sensor device for the detection of a chemical agent in a liquid sample, the method comprising the steps of:
(a) depositing a conductive layer onto an insulating or semiconducting substrate, whereby the conductive layer forms a pattern comprising first and second microelectrodes and having a gap between the first and second microelectrodes; (b) forming a microfluidic channel that covers a portion of the substrate, encloses the gap, and is fluidically connected on one side of the gap to an inlet port and on another side of the gap to an outlet port; (c) flowing an aqueous suspension of SWNT through said inlet port to fill said enclosed gap with said aqueous suspension; (d) applying an AC voltage between the first and second microelectrodes, whereby SWNT are dielectrophoretically assembled across the gap and form an electrical connection at one end of the SWNT with the first microelectrode and at another end of the SWNT with the second microelectrode; and (e) removing said aqueous suspension of SWNT from the microfluidic channel.

11 . The method of claim 10 , wherein step (b) comprises:
(b1) forming a microfluidic channel in polydimethylsiloxane (PDMS) using SU-8 replica molding and photolithography; (b2) exposing the microfluidic channel and the substrate to an oxygen plasma for about 30 seconds; (b3) bonding the microfluidic channel to the substrate at about 150° C. for about 15 minutes.

12 . The method of claim 10 , wherein a plurality of first and second microelectrode pairs is formed, each pair having a gap between the microelectrodes of the pair, and the gap is enclosed by the microfluidic channel; and whereby SWNT are dielectrophoretically assembled across each gap and form an electrical connection at one end of the SWNT with the first microelectrode of each pair and at another end of the SWNT with the second microelectrode of each pair.

13 . The method of claim 12 , wherein steps (c) through (e) are repeated for one or more cycles of SWNT assembly; wherein at each performance of step (d) the voltage is applied between a different pair of microelectrodes; wherein for each performance of steps (c) and (d) the SWNT are differently functionalized, whereby a multiplex sensor is fabricated.

14 . The method of claim 10 , further comprising:
(f) attaching to the substrate a detection circuit connected to said first and second microelectrodes and capable of detecting a change in an electrical property of the SWNT.

15 . The method of claim 14 , further comprising:
(g) attaching to the substrate a wireless transmitter capable of transmitting an output signal from said detection circuit to a remote receiver.

16 . The method of claim 14 , further comprising:
(g) attaching to the substrate a data processing module capable of processing an output signal from said detection circuit and outputting a signal that provides information on the presence and/or amount of said chemical agent.

17 . The method of claim 16 , further comprising:
(h) attaching to the substrate a wireless transmitter capable of transmitting an output signal from said data processing module to a remote receiver.

Assignees

• Univ Northeastern

Inventors

• Wang Ming
• Liu Yu
• Dokmeci Mehmet Remzi

Classifications

• H10P14/00

  Formation of materials, e.g. in the shape of layers or pillars · CPC title

• G01N33/18 Primary

  Water · CPC title

• G01N27/07

  Construction of measuring vessels; Electrodes therefor · CPC title

• B03C5/005 Primary

  Dielectrophoresis, i.e. dielectric particles migrating towards the region of highest field strength · CPC title

• A61B5/1473

  invasive, e.g. introduced into the body by a catheter · CPC title