Needle assembly for transdermal administration and method of producing the same

1. A needle assembly for transdermal administration, comprising:

a substrate having a first surface and a second surface opposite to the first surface; and

a plurality of fine needles projecting perpendicularly from the first surface and positioned in a matrix on the first surface of the substrate at regular intervals along a longitudinal direction and a lateral direction of the first surface,

wherein the substrate has a plurality of first grooves formed between the plurality of fine needles on the first surface and a plurality of second grooves formed on the second surface such that the plurality of second grooves is positioned to correspond to positions of the plurality of fine needles and offset from the plurality of first grooves and has a depth that does not fluidly connect to the plurality of first grooves in a thickness direction of the substrate, such that the substrate deforms to follow a surface shape of a skin and such that the plurality of first grooves and the plurality of second grooves allow axes of the plurality of fine needles to extend in a direction normal to the surface of the skin, the plurality of first grooves includes a set of grooves extending in a first direction between adjacent ones of the plurality of fine needles, and arrayed along a second direction perpendicular to the first direction, and the plurality of second grooves includes a set of grooves extending in a third direction, and arrayed along a fourth direction perpendicular to the third direction.

2. The needle assembly of claim 1 , wherein each of the plurality of first grooves and the plurality of second grooves has at least one cross section selected from trapezoidal, rectangular, triangular, semicircular, and semielliptical in a direction perpendicular to a direction in which each of the plurality of first grooves and the plurality of second grooves extend.

3. The needle assembly of claim 1 , wherein the plurality of first grooves includes a second set of grooves extending in the second direction perpendicular to the first direction.

4. The needle assembly of claim 3 , wherein the plurality of second grooves includes a second set of grooves extending in the fourth direction perpendicular to the third direction.

5. The needle assembly of claim 4 , wherein the plurality of first grooves is formed such that the first direction is the longitudinal direction of the first surface, and the plurality of second grooves is formed such that the third direction is a longitudinal direction of the second surface.

6. The needle assembly of claim 4 , wherein the plurality of first grooves is formed such that the first direction is the longitudinal direction of the first surface, and the plurality of second grooves is formed such that the third direction is a diagonal direction of the second surface.

7. The needle assembly of claim 1 , wherein the plurality of first grooves is formed such that the first direction is the longitudinal direction of the first surface.

8. The needle assembly of claim 1 , wherein the plurality of first grooves is formed such that the first direction is the lateral direction of the first surface.

9. The needle assembly of claim 1 , wherein the plurality of first grooves is formed such that the first direction is a diagonal direction of the first surface.

10. The needle assembly of claim 1 , wherein the plurality of second grooves is formed such that the plurality of second grooves is positioned to substantially correspond to the axes of the plurality of fine needles on the first surface of the substrate.

11. The needle assembly of claim 10 , wherein the plurality of first grooves includes a second set of grooves extending in the second direction perpendicular to the first direction, and the plurality of second grooves includes a second set of grooves extending in the fourth direction perpendicular to the third direction.

12. The needle assembly of claim 10 , wherein the plurality of first grooves is formed such that the first direction is the longitudinal direction of the first surface.

13. The needle assembly of claim 10 , wherein the plurality of first grooves is formed such that the first direction is the lateral direction of the first surface.

14. The needle assembly of claim 10 , wherein the plurality of first grooves is formed such that the first direction is a diagonal direction of the first surface.

15. The needle assembly of claim 1 , wherein the plurality of first grooves is formed such that each of the plurality of first grooves has a length that is less than a length of the first surface of the substrate in a direction in which each of the plurality of first grooves extends.

16. The needle assembly of claim 1 , wherein the plurality of first grooves is formed such that adjacent first grooves are spaced apart from each other by two adjacent fine needles.

17. The needle assembly of claim 1 , wherein the plurality of first grooves is formed such that adjacent first grooves are spaced apart from each other by three adjacent fine needles.

18. The needle assembly of claim 1 , wherein the plurality of second grooves is formed such that the first direction is the longitudinal direction of the first surface, and the third direction is one of a longitudinal direction and a lateral direction of the second surface.

19. A method of producing a needle assembly for transdermal administration, comprising:

placing a polymer material on a surface of a reproduction plate having a flat part, a plurality of recesses corresponding to a plurality of fine needles, and a plurality of projections corresponding to a plurality of first grooves;

heating the polymer material such that the polymer material melts on the reproduction plate;

pressing the polymer material with a press having a flat surface portion facing the flat part of the reproduction plate and a plurality of projecting portions formed offset from the plurality of projections of the reproduction plate such that the plurality of projecting portions corresponds to a plurality of second grooves;

curing the polymer material on the reproduction plate such that a needle assembly is formed; and

releasing the needle assembly from the reproduction plate to obtain the needle assembly comprising a substrate having a first surface and a second surface opposite to the first surface, and the plurality of fine needles projecting perpendicularly from the first surface and positioned in a matrix on the first surface of the substrate at regular intervals along a longitudinal direction and a lateral direction of the first surface,

wherein the substrate has the plurality of first grooves formed between the plurality of fine needles on the first surface and the plurality of second grooves formed on the second surface such that the plurality of second grooves is positioned to correspond to positions of the plurality of fine needles and offset from the plurality of first grooves and has a depth that does not fluidly connect to the plurality of first grooves in a thickness direction of the substrate, such that the substrate deforms to follow a surface shape of a skin and such that the plurality of first grooves and the plurality of second grooves allow axes of the plurality of fine needles to extend in a direction normal to the surface of the skin, the plurality of first grooves includes a set of grooves extending in a first direction between adjacent ones of the plurality of fine needles, and arrayed along a second direction perpendicular to the first direction, and the plurality of second grooves includes a set of grooves extending in a third direction, and arrayed along a fourth direction perpendicular to the third direction.

20. The method of claim 19 , wherein the polymer material is a biocompatible thermoplastic resin.