Method of fabricating valve unit in a microfluidic device

1. A method of fabricating a valve unit, the method comprising:

forming a lower substrate comprising a channel including a first region and a second region which is deeper than the first region and is adjacent to one side of the first region;

forming an upper substrate comprising a valve material chamber which extends only partially through the upper substrate;

after the forming of the upper substrate, filling the valve material chamber with a valve material and curing the valve material in the valve material chamber;

attaching a surface of the upper substrate in which the valve material chamber is formed to a surface of the lower substrate in which the channel is formed, so that the valve material chamber overlaps an overlapped portion of the first region, and does not overlap a non-overlapped portion of the first region;

melting the valve material accommodated in the valve material chamber to flow the valve material into the non-overlapped portion of the first region; and

curing the valve material flowed into the non-overlapped portion to close the first region.

2. The method of claim 1 , wherein the channel of the lower substrate further includes a third region which is deeper than the first region and is adjacent to another side of the first region.

3. The method of claim 2 , wherein the attaching the upper substrate to the lower substrate comprises attaching the upper and lower substrates so that the non-overlapped portion of the first region is adjacent to the third region and the overlapped portion of the first region is adjacent to the second region.

4. The method of claim 1 , wherein lower substrate further comprises a chamber including a third region which is deeper than the first region and is adjacent to another side of the first region.

5. The method of claim 4 , wherein the attaching the upper substrate to the lower substrate comprises attaching the upper and lower substrates so that the non-overlapped portion of the first region is adjacent to the third region and the overlapped portion of the first region is adjacent to the second region.

6. The method of claim 1 , wherein each of the lower substrate and the upper substrate is formed by molding a thermoplastic resin.

7. The method of claim 1 , wherein the valve material comprises a phase transition material that is in a solid state at room temperature and melts when heated.

8. The method of claim 7 , wherein the valve material further comprises a plurality of micro heating particles which are dispersed in the phase transition material and generate heat when subjected electromagnetic energy.

9. The method of claim 8 , wherein the micro heating particles comprise metal oxide particles.

10. The method of claim 6 , wherein the phase transition material comprises a wax, a gel, or a thermoplastic resin.

11. The method of claim 1 , wherein the attaching the upper substrate to the lower substrate comprises attaching the upper and lower substrates so that the valve material chamber overlaps a portion of the second region.

12. A method of fabricating a valve unit, the method comprising:

attaching a first surface of a first substrate to a second surface a second substrate, wherein the first substrate includes a channel which is formed in the first surface and has a stepped region which protrudes from a bottom surface of the channel, the second substrate includes a cavity which is formed in the second surface and extends only partially through the second substrate, the cavity overlaps a first portion of the stepped region of the channel and does not overlap a second portion of the stepped region of the channel, and the cavity contains a material that is injected and cured after forming the second substrate;

melting the material accommodated in the cavity so that the material flows from the cavity to the second portion of the stepped region of the channel to close the channel.

13. The method of claim 12 , wherein a depth of the channel in the stepped region is less than a depth of the channel in a region of the channel adjacent to the stepped region.

14. The method of claim 12 , wherein the attaching the first substrate to the lower substrate comprises attaching the upper and lower substrates such that the cavity extends past the first portion of the stepped region of the channel.

15. The method of claim 12 , wherein the melting the material comprises irradiating the material with electromagnetic energy to heat the material.

16. The method of claim 12 , wherein each of the lower substrate and the upper substrate is formed by molding a thermoplastic resin.

17. The method of claim 12 , wherein the material comprises a phase transition material that is in a solid state at room temperature and melts when heated.

18. The method of claim 17 , wherein the phase transition material comprises a wax, a gel, or a thermoplastic resin.

19. The method of claim 17 , wherein the material further comprises a plurality of micro heating particles which are dispersed in the phase transition material and generate heat when subjected electromagnetic energy.

20. The method of claim 19 , wherein the micro heating particles comprise metal oxide particles.