Housing surface with tactile friction features

1. An electronic device comprising:

an enclosure defining an internal volume and having a glass structure at least partially defining a touch-sensitive exterior surface of the electronic device, the touch-sensitive exterior surface comprising:

a base surface defining a first planar region having a first area; and

a set of tactile friction features distributed along the touch-sensitive exterior surface and extending from the base surface to define:

a plurality of substantially flat tops, the plurality of substantially flat tops defining a second planar region having a second area less than the first area;

a micro-scale average width; and

a height defined by an offset between the second planar region and the first planar region, the height less than the micro-scale average width; and

a touch sensor positioned below the glass structure and configured to detect a touch gesture along the touch-sensitive exterior surface, the set of tactile friction features providing a frictional resistance to the touch gesture.

2. The electronic device of claim 1 , wherein:

each tactile friction feature of the set of tactile friction features has a circular contour defining a diameter ranging from 1 micron to 20 microns; and

the height is less than or equal to 5 microns.

3. The electronic device of claim 1 , wherein:

the electronic device further comprises a display positioned under the glass structure;

the glass structure comprises:

a first region positioned over a visible portion of the display; and

a second region at least partially surrounding the first region and not positioned over the visible portion of the display;

the set of tactile friction features is a first set of tactile friction features positioned along the first region;

the electronic device further comprises a second set of tactile friction features positioned along the second region; and

a first pitch between tactile friction features of the first set of tactile friction features is greater than a second pitch between tactile friction features of the second set of tactile friction features.

4. The electronic device of claim 3 , wherein:

the first pitch is measured as an average distance between centers of adjacent tactile friction features; and

the first pitch is between 5 and 600 microns.

5. The electronic device of claim 1 , wherein:

the touch gesture is provided by a user's finger in contact with the touch-sensitive exterior surface; and

the set of tactile friction features prevents the user's finger from contacting the base surface.

6. An electronic device comprising:

a display;

a touch sensor positioned over the display; and

an enclosure comprising a glass structure enclosing the display and defining an exterior surface of the electronic device, a touch-sensitive region of the exterior surface of the electronic device positioned over the touch sensor and defining a substantially planar base surface and a set of glass tactile friction features extending from the substantially planar base surface, each glass tactile friction feature of the set of glass tactile friction features including:

a base having a micro-scale width;

a top;

a sidewall extending from the base to the top; and

a height between the base and the top, the height being less than or equal to the micro-scale width,

wherein:

the tops of multiple glass tactile friction features of the set of glass tactile friction features are substantially flat; and

the set of glass tactile friction features are configured to provide a frictional resistance to a touch applied to the touch-sensitive region.

7. The electronic device of claim 6 , wherein:

the set of glass tactile friction features is substantially evenly distributed over the touch-sensitive region;

and

the frictional resistance is due, at least in part, to contact between a user's finger and the tops of the multiple glass tactile friction features of the set of glass tactile friction features.

8. The electronic device of claim 6 , wherein the substantially planar base surface includes an interstitial region that defines a substantially random spacing between the bases of adjacent pairs of the set of glass tactile friction features.

9. The electronic device of claim 7 , wherein:

the touch includes a gesture; and

the user's finger does not touch the substantially planar base surface when performing the gesture.

10. The electronic device of claim 8 , wherein an average spacing between adjacent bases along the substantially planar base surface is less than an average width of micro-scale widths of the bases.

11. The electronic device of claim 6 , wherein an average height of the set of glass tactile friction features ranges from 50 nm to 2 μm.

12. The electronic device of claim 6 , wherein:

the sidewall defines a conical portion and an oblique internal taper angle of each glass tactile friction feature.

13. The electronic device of claim 12 , wherein:

the set of glass tactile friction features is a first set of glass tactile friction features having a first height;

the exterior surface of the electronic device has a second set of glass tactile friction features that is interspersed with the first set of glass tactile friction features; and

the first height of the first set of glass tactile friction features is greater than a second height of the second set of glass tactile friction features.

14. The electronic device of claim 6 , wherein the enclosure further comprises an oleophobic coating including a fluorinated material bonded to the set of glass tactile friction features.

15. An electronic device comprising:

a display;

a touch sensor; and

an enclosure at least partially surrounding the display and including a glass structure defining a touch-sensitive input region positioned over the touch sensor, the touch-sensitive input region defining:

a substantially flat base surface; and

a set of tactile friction features extending outward from the substantially flat base surface and defining:

a plurality of substantially flat top surfaces having an average width ranging from 1 to 20 microns and at least partly providing a frictional resistance to the touch-sensitive input region;

an average height less than or equal to the average width; and

adjacent pairs of tactile friction features of the set of tactile friction features having circular bases separated by an interstitial region of the substantially flat base surface.

16. The electronic device of claim 15 , wherein:

the glass structure is positioned over both the display and the touch sensor;

the glass structure includes a display window region;

the set of tactile friction features is distributed along the display window region; and

the touch sensor is configured to detect a touch on the glass structure along the display window region.

17. The electronic device of claim 15 , wherein:

the interstitial region defines an average spacing between adjacent tactile friction features; and

a ratio of the average height to the average spacing of the set of tactile friction features ranges from 0.005 to 10.

18. The electronic device of claim 17 , wherein each tactile friction feature of the set of tactile friction features has a circular contour and each of the plurality of substantially flat top surfaces is offset from the substantially flat base surface by a distance of less than or equal to 2 microns.

19. The electronic device of claim 15 , wherein:

the set of tactile friction features has a uniform width; and

the uniform width is smaller than a pixel size of the display.

20. The electronic device of claim 15 , wherein the set of tactile friction features is configured to allow finger contact with top surfaces of an adjacent pair of tactile friction features without contacting the interstitial region of the substantially flat base surface.