MICROFLUIDIC DEVICES AND METHODS OF MANUFACTURING

1 . A method for producing a microfluidic device, comprising:

depositing a photoresist material onto a carrier substrate;

patterning the deposited photoresist material to have a target pattern on the carrier substrate;

transferring the target pattern from the carrier substrate to a first mold of a first polymeric material;

forming a second mold of a second polymeric material with the first polymeric mold, the second mold having a mold pattern corresponding to the target pattern, wherein the second polymeric material is different than the first polymeric material; and

imprinting a substrate with the mold pattern using the second mold, the substrate having a polymeric substrate material.

2 . The method of claim 1 further comprising bonding the imprinted substrate with a cover using a solvent, the cover having the same polymeric substrate material.

3 . The method of claim 2 , further comprising removing residual solvent to increase transparency after bonding the imprinted substrate with the cover.

4 . The method of claim 1 wherein the polymeric substrate material includes poly(methyl methacrylate), and the method further includes bonding the imprinted substrate with a cover using a solvent selected from the group consisting of isopropanol, n-butanol, and cyclohexanol.

5 . The method of claim 1 wherein the polymeric substrate material includes polystyrene, and the method further includes bonding the imprinted substrate with a cover using a solvent selected from the group consisting of isopropanol, n-butanol, cyclohexanol.

6 . The method of claim 1 wherein the polymeric substrate material includes polycarbonate, and the method further includes bonding the imprinted substrate with a cover using a solvent selected from the group consisting of dimethylformamide, ethanol, diethyl ether, n-heptane.

7 . The method of claim 1 wherein the polymeric substrate material includes cyclo-olefin copolymer, and the method further includes bonding the imprinted substrate with a cover using a solvent selected from the group consisting of cyclohexane, ethylactate, diacetone alcohol, 1,2 dichloropropane, carbon tetrachloride, xylene, and toluene.

8 . A method for method for producing a microfluidic device, comprising:

forming a target structural pattern on a substrate, the substrate having a polymeric substrate material with a solubility parameter;

selecting a bonding solvent based on a difference between the solubility parameter of the polymeric substrate material and a solubility parameter of the bonding solvent; and

bonding the substrate having the target structural pattern with a cover using the selected bonding solvent.

9 . The method of claim 8 wherein selecting the bonding solvent includes:

determining a difference between the solubility parameter of the polymeric substrate material and a solubility parameter of a candidate solvent; and

if the determined difference is less than about 1.0 (cal/cm 3 ) 0.5 , selecting the candidate solvent as the bonding solvent.

10 . The method of claim 8 wherein selecting the bonding solvent includes:

determining a difference between the solubility parameter of the polymeric substrate material and a solubility parameter of a candidate solvent; and

based on the determined difference, predicting solubility of the polymeric substrate material in the candidate solvent.

11 . The method of claim 8 wherein selecting the bonding solvent includes:

calculating an enthalpy change as follows:

Δ H =(δ 1 −δ 2 ) 2 φ 1 φ 2 V

where δ 1 and φ 1 are a solubility parameter and a volume fraction of component 1, respectively, δ 2 and φ 2 are a solubility parameter and a volume fraction of component 2, respectively, and V is a mixture volume of the candidate solvent and the polymeric substrate material; and

calculating a free energy change of mixing as follows:

Δ G=ΔH−TΔS

where ΔG is a change in Gibbs free energy, ΔH is a change in enthalpy, T is an absolute temperature, and ΔS is a change in entropy on mixing; and

predicting solubility of the polymeric substrate material in the candidate solvent based on the calculated free energy change.

12 . The method of claim 8 wherein bonding the substrate includes bonding the substrate having the target structural pattern with the cover using the selected bonding solvent without protecting the target structural pattern with a sacrificial material.

13 . The method of claim 8 wherein bonding the substrate includes:

bonding the substrate having the target structural pattern with the cover using the selected bonding solvent without protecting the target structural pattern with a sacrificial material; and

fastening the cover to the substrate with the formed bond generally without damage to the target structural pattern on the substrate.

14 . The method of claim 8 wherein:

the polymeric substrate material includes poly(methyl methacrylate) having a solubility parameter of about 9.3 (cal/cm 3 ) 0.5 ; and

selecting the bonding solvent includes selecting a solvent with a solubility parameter greater than about 8.3 (cal/cm 3 ) 0.5 and lower than about 11.6 (cal/cm 3 ) 0.5 .

15 . The method of claim 8 wherein bonding the substrate includes bonding the substrate having the target structural pattern with a cover using the selected bonding solvent, the cover having the same polymeric substrate material as the substrate.

16 . A method for method for producing a microfluidic device, comprising:

forming a target structural pattern on a substrate, the substrate having a polymeric substrate material;

bonding the substrate having the target structural pattern with a cover using a bonding solvent at a bonding temperature, wherein a difference in solubility parameter between the polymeric substrate material and the bonding solvent is lower than about 1.0 (cal/cm 3 ) 0.5 ; and

controlling the bonding temperature based on a free energy change corresponding to the polymeric substrate material dissolving in the bonding solvent.

17 . The method of claim 16 wherein controlling the bonding temperature includes:

calculating an enthalpy change as follows:

Δ H =(δ 1 −δ 2 ) 2 φ 1 φ 2 V

where δ 1 and φ 1 are a solubility parameter and a volume fraction of component 1, respectively, δ 2 and φ 2 are a solubility parameter and a volume fraction of component 2, respectively, and V is a mixture volume of the candidate solvent and the polymeric substrate material;

with the calculated enthalpy change, calculating a free energy change of mixing as follows:

Δ G=ΔH−TΔS

where ΔG is a change in Gibbs free energy, ΔH is a change in enthalpy, T is an absolute temperature, and ΔS is a change in entropy on mixing; and

controlling the bonding temperature based on the calculated Gibbs free energy.

18 . The method of claim 16 wherein controlling the bonding temperature includes selecting a bonding temperature such that the target structural pattern on the substrate is generally not damaged during bonding.

19 . The method of claim 16 wherein bonding the substrate includes bonding the substrate with the cover without using a sacrificial material on the substrate, and wherein controlling the bonding temperature includes selecting a bonding temperature such that the target structural pattern on the substrate is generally not damaged during bonding.

20 . The method of claim 16 wherein controlling the bonding temperature includes controlling the bonding temperature based at least in part on the difference in solubility parameter between the polymeric substrate material and the bonding solvent.