Dwaine A. Braasch, Eric B. Williams, James W. Rawlins1 and Steve McDaniel2
Touch screens are ubiquitous in modern electronic world and are quickly being adapted to more and more devices which previously lacked touch interface. The rapid adaptation of touch-based technology has created a market need
for human smudge and residue minimization. The residual fingerprint from direct contact with these devices has resulted in
a common aggravation . To counter this persistent and pervasive problem, manufacturers are rapidly developing different technologies to reduce the appearance of fingerprints and
contact residue. One technique to improve image clarity has
been to reduce the gloss and refractive index difference between
the contact surface and the residue as a means to diminish the
visual impact. Another surface modification method is based
in decreasing the coating surface energy to reject wetting of fingerprint oils most often via an oleophobic material. The poor
wetting of fingerprints by oleophobic materials often results in
an increase in difference of refractive index between the coated
surface and the finger oil, which is easier to clean, yet more visually noticeable. Each of these methods leave the residue chemically unchanged.
In an attempt to improve residue control technologies, after
market temporary foil appliques have become commonplace
as a means to reduce device damage and control human and
other residue without replacing the entire device. Reactive
Surfaces has successfully engineered an additive specifically to
impart self-cleaning functionality to almost any surface, e.g.,
original equipment manufacturers (OEM) and aftermarket foil
appliques. The Reactive Surfaces additive has been successfully
reduced to practice in solvent and waterborne coatings that
can be applied to virtually any material substrate. The unique
difference between Reactive Surfaces’ technology occurs when
the residue is chemically and catalytically converted, resulting
in a surface that is more self-cleaning with use. The chemically
converted residue shifts from hydrophobic to more hydrophilic, and thus increases the compatibility between the residue
and the coated surface and decreases the refractive index difference between the coating and the residual fingerprint. The
fingerprint appearance is noticeably reduced and is easier to
wipe from the surface.
When human fingers contact an object, many substances transfer to the surface of the object and leave behind fingerprints. The
substances on human fingerprints can arise endogenously from the
sweat glands within the skin surface of a finger or exogenously
from foreign materials like cosmetics, perfumes, food residues,
and substances from other glands. The combination of these endogenous and exogenous materials, along with the environmental
conditions such as humidity and temperature, cause a fingerprint
on a surface to be increasingly visible. As a strategy to counter
the annoyance of accumulated residual fingerprints, we developed
coatings for non-porous surfaces, i.e., screen protectors appliques
for any touchscreen device.
The palms of human hands and the soles of human feet are
covered by skin with patterns that can enhance frictional forces
between skin and contacted surfaces. The skin topography greatly
assists human activities, like walking, holding, and picking-up articles. Skin without hair or sebaceous glands and with ridges is collectively termed frictional ridge skin (Figure 1). Sweat glands are
Anti-Fingerprint Strategies for
Post-Deposition of Fingerprints
on Non-porous Surfaces
Fig. 1.
Digital light micrograph
of human finger ridges at
100X magnification*
Fig 2.
Digital microscopic view
of sweat (perspiration)
secreted from the pores on
a friction ridge skin at 150X
magnification.*
