Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
This invention relates generally to toys, games,
and other play devices, and more particularly to play devices
which exploit the behavior of water on superhydrophobic surfaces.
A hydrophobic substance is one having a distinct
tendency to repel water in a manner usually characteristic
of non-wetted, oily, waxy or fatty materials. A hydrophobic
surface will normally not sustain a water film, even one of
monomolecular thickness. This property not only is found in
all oils, fats, waxes and many resins, but also in finely
divided powders such as carbon black and magnesium carbonate.
A hydrophilic substance has a strong affinity for water
by absorption or adsorption even to the point of gradual
liquifaction by extracting water vapor from the atmosphere.
This property is characteristic of carbohydrates such as algin,
vegetable gums, pectins and starches as well as complex
proteins like gelatin and albumen.
The present invention deals with a hydrophobic layer
formed on a substrate, which layer incorporates particles of
hydrophobic fumed silicon dioxide (HFSD). Silicon dioxide
particles are produced by the hydrolysis of silicon tetrachloride
in a flame process. The fumed silicon dioxide particle is
hydrophilic in nature by reason of the large number of hydroxyl
groups present on the surface. These particles are rendered
,
hydrophobic by reacting them with a silane. During the
reaction, hydrophobic hydrocarbon groups replace many of the
hydroxyl groups, the resulting particles offering increased
compatibility with organic or non-polar media and a correspond-
ing repulsion to water. One commercially available form of hydro-
phobic fumed silicon dioxide powder is manufactured and sold
by Cabot Corporation of Boston, Massachusetts, under the
trademark "Silanox'!.
Silane, which is a member of the silicone family,
contributes its inherent hydrophobicity and oleophilicity to
the HFSD particle. Fumed silicon dioxide, which is a fine
pure powder, brings to HFSD a particle of extremely small
size and enormous surface area, all of it being accessible
for interaction with the surrounding media. In protective
coatings, the hydrophobicity derived from the silane component
of HFSD is augmented by the surface micro-roughness imparted
by the silicon dioxide component, giving rise to a degree
of water repellency so great that it is often referred to as
super-hydrophobicity.
Substrates coated with HFSD repel water to an extraordi-
nary degree. An air layer becomes entrapped between the
substrate and the water and is visible as a reflected silvery
sheen. This air layer or shield is sometimes referred to as
a gaseous plastron.
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The super-hydrophobic properties of HFSD can be
imparted to substrates in various ways. HFSD particles can,
for example, be applied in dry form on tacky surfaces, or it
can be applied from a liquid dispersion. But regardless of
the mode of applying HFSD to the substrate, it is important
that these particles remain essentially uncoated and exposed
at the solid-water interface to afford the micro-roughness
necessary for optimum super-hydrophobicity.
One serious difficulty often encountered in HFSD
coatings is its poor abrasion resistance, for if the coating
is subjected to wear, it may be eroded, with a consequent
loss of super-hydrophobicity and a possible gain in hydrophilic
properties should the underlying substrate be hydrophilic in
character.
In applicant's prior United States Patent 3,931,428
issued January 6th, 1976, there is disclosed a technique for
coating substrates to render the face thereof super-hydrophobic,
the resultant face being highly abrasion and scratch resistant.
This is accomplished by applying to the face of a
substrate which has a micro-rough surface, particles of hydro-
phobic fumed silicon dioxide dispersed in a solvent within
which is dissolved a resinous binder whose amount, by weight,
is substantially less than one-half of the amount of particles
in the dispersion. Upon volatilization of the solvent, the
resultant coating is composed predominantly of fumed silicon
dioxide particles strongly bonded to the face of the substrate.
S~MMARY OF INVENTION
The present invention provides a play machine
comprising:
(a) a pinball type play board having a play area
provided with obstacles which upon impact act to dissect a
water ball into smaller balls and to deflect them in various
directions, the surface of the play board being coated with
super-hydrophobic material having virtually no force of
adhesion with respect to water whereby a drop of water placed
on the board is caused to assume a spherical form;
(b) a shooting chamber formed on the board at a
corner thereof to receive a drop of water which forms into a
ball, said chamber having a spring actuated retractable plunger
associated therewith whereby when the plunger ls released it
propels the water ball into a play area to strike one of
said obstacles, the resulting smaller balls then shooting in
various directions; and
(c) a plurality of electrical contact pairs
disposed at predetermined positions in the play area, each
contact pair, when bridged by a ball, closing a circuit to
indicate a score.
The play device exploits the natural repulsion
existing between hydrophobic and hydrophilic surfaces to
create an air cushion therebetween which minimizes friction
encountered in a sliding movement of the hydrophilic surface
relative to the hydrophobic surface.
OUTLINE OE DRAWING
For a better understanding of the invention as well
as other objects and further features thereof, reference is
made to the following detailed description to be read in
conjunction with the accompanying drawings, wherein:
463
Figure 1 is a plan view of a water-ball maze in accordance with
the invention;
Figure 2 is a section of a chalmel included in the maze;
Figure 3 is a plan view of a water-ball pinball-type machine in
accordance with the invention;
Figure 4 is a sketch of a slide in which the hydrophilic surface
of a vehicle engages the super-hydrophobic surface of a trackway in accor-
dance with the invention; and
Figure 5 illustrates the relationship between the hydrophilic and
hydrophobic surfaces of the arrangement shown in Figure 4.
DESCRIPTION OF INVENTION
-
The Super-Hydrophobic Surface:
In determining the degree of hydrophobicity presented by a given
surface, one must take into account two opposing forces. First there is the
force of cohesion which is present in the water on the surface, this co-
hesive force causing water molecules to attract each other. The second
force acting on the water is the force of adhesion which causes water mole-
cules to attract the atoms or molecules on the surface. The relationship
between these two opposing forces determines the degree of wetting of the
surface by the water.
On a normally hydrophobic surface, such as wax paper, a drop of
water retains its integrity, but there is sufficient surface adhesion to
cause the drop to assume a somewhat flattened form on the wax paper. On a
superhydrophobic surface formed by an HFSD coating or layer, the shape of
the water drop is almost spherical, in that the force of adhesion is almost
negligible. On a completely wettable and hydrophilic surface, the force
of adhesion is stronger than the force of cohesion and a water drop will
quickly spread to cover the surface. Thus with hydrophobic surfaces the
cohesive force is dominant, and in such surfaces water droplets tend to
draw together, whereas in the hydrophilic surfaces the adhesive force is
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1'11 ~8~63
greater and overcomes the cohesive force.
Two factors come into play in determining the degree to which a
surface is hydrophobic. First there is the chemical factor which is why
oily, waxy or fatty materials repel water. But there is also a physical
factor; for when surface roughness is present to create minute projections
or fibrils, a water droplet tends to be supported only on the peaks of the
projections. The air-filled troughs between the projections are free from
contact with the water~ thereby enhancing hydrophobicity. Exceptional water
repellency or super-hydrophobicity may therefore be obtained by a merger of
surface chemistry and micro-roughness. This phenomenon is often encountered
in nature, such as on leaves and petals wherein a multiplicity of tiny hy-
drophobic fibrils act to repel water, thereby facilitating transpiration.
In the present invention, both the chemical and physical factors
are exploited to provide a super-hydrophobic layer which is abrasion and
scratch resistant and cannot easily be rubbed off, whereby the character-
istics of the layer are maintained under rigorous operating conditions. In
order to accomplish this result, it is essential that the substrate which is
coated with HFSD also exhibit hydrophobic properties. We shall, therefore,
first consider the nature of the substrate.
Substrates:
-
One preferred form of substrate material is a layer of foam plastic
formed of polyethylene or polypropylene having a very fine cell structure.
Usable for this purpose is "Minicel" L-200, crosslinked polyethylene foam
manufactured and sold by ~lercules Incorporated of Wilmington, Del. A block
of such foam material is skived to provide a layer sheet, thereby cutting
open the cells in the face of the layer to create a multiplicity of fine
pockets. As a consequence of these fine pockets, the face of the layer
presents a myriad of cut-ends or projections which are inherently hydrophobic
in character.
Another useful form of substrate is spunbonded olefin formed of
high-density polyethylene fibers. Sheets or layers of this material are
formed by first spinning continuous strands of very fine interconnected
fibers and then bonding them together with heat and pressure. Though the
dense packing of the fine, interconnected fibers produces a seemingly smooth
surface, the surface is actually porous and has a very fine fuzz or uncut
pile face which imparts thereto hydrophobic properties. One commercial form
of spunbonded olefin is manufactured and sold by the DuPont Company under
the trademark "TYVEK". As noted in the DuPont Technical Information Bulle-
tin S-9, published March 1973, "The Properties and Processing of Tyvek Spun-
bonded Olefin", this material is inherently hydrophobic.
Similar characteristics are found in spunbonded polyester sheetsor layers formed by continuous filament polyester fibers that are randomly
arranged, highly dispersed and bonded at the filament junctions. When these
fibers are crimped, the resultant surface is fuzzy, imparting thereto a high
degree of hydrophobicity. This product, which is manufactured and sold by
DuPont under the trademark REEMAY, is described in the DuPont Technical Bul-
letin S-4, dated April 1970, "Properties and Processing of REEMAY Spunbonded
Polyester".
In summary, the substrate to be coated by HFSD is formed of a ma-
terial which is chemically hydrophobic and which has a micro-rough face
which is physically hydrophobic, so that both hydrophobic factors are com-
bined in the fine hairs or projections which constitute the face of the ma-
terial. The term "micro-rough" as used in the specification and claims is
intended to encompass any facial texture which is physically hydrophobic,
such as cusps, piles, projections, cut-ends, flock and fibrils.
Substrate Coatings:
The face of the substrate is sprayed or otherwise coated with
hydrophobic fumed silicon dioxide particles dispersed in a solvent that is
chemically hydrophobic, within which solvent is dissolved a resinous, thermo-
plastic binder that is chemically hydrophobic. Thus when the coating is
1~18~
dried or cured, all constituents thereof, including trace elements, are
hydrophobic in character, and the resultant treated substrate is super-
hydrophobic and highly resistant to abrasion and other damaging effects.
Thus even when an area of the superhydrophobic surface becomes eroded, the
exposed area remains hydrophobic, and in no instance is a hydrophilic area
created because of wear or abrasion.
A preferred form of HFSD is Silanox 101 manufactured by Cabot
Corporation, which is a silane-modified silicon dioxide in finely divided
powder form. The surface of this powder is 225 m2/gm (BET), the primary
particle size is 7 ~, and the bulk density is 3 lbs. per cubic foot.
In order to form a dispersion of the HFSD particles, use is made
of a solvent which is inherently hydrophobic and capable of dissolving the
binder for the HFSD particles. A preferred solvent for this purpose is tri-
chloroethylene (CH Cl: CC12), which is a stable, colorless heavy liquid
derived from tetrachloroethane by treatment with lime or alkali in the pres-
ence of water, or by thermal decomposition followed by steam distillation.
Also usable as a solvent is perchloroethylene (C12 C: CC12) or benzene
(C6H6) .
The preferred form of binder which is dissolved in the solvent is
high impact polystyrene (C6H5CHCH2), which is a thermoplastic synthetic
resin of variable molecular weight depending on the degree of polymeriza-
tion. Also usable as a binder are polyvinyl resin or copolymers of ethylene
and vinyl acetate. These binders are all thermoplastic in nature and have
hydrophobic properties.
It is important that the amount of binder by weight be no more
than is necessary to effectively bond the HFSD particles to the face of the
substrate so that the resultant covering is predominantly HFSD and is super-
hydrophobic. Thus the ratio of the binder by weight to the HFSD particles
must be less than 50:50.
One acceptable formulation for the dispersion is the following:
34G3
Solvent--1500 cc of trichloroethylene
Binder--20 grams of high impact polystyrene
HFSD--35 grams of Silanox
In practice, the amount of binder in this formation may be further
reduced to as low as 10 grams relative to 35 grams of Silanox.
In preparing the dispersion, the binder is first fully dissolved
in the solvent, and then the HFSD particles are added to the solvent in a
Waring blender or other suitable mixer and stirred therein for a few seconds
to completely disperse same without excessive agitation. In applying this
dispersion to the face of a substrate, a wet spray technique may be used.
When the solvent volatilizes, strongly bound to the fibrils or the cut-ends
of the substrate face is a fine coating containing HFSD particles. The re-
sultant surface is extraordinarily water-repellent and resistant to abrasion
and other wear conditions.
In those instances where the surface may be subjected to very
heavy wear, its abrasion resistance may be augmented by a calendering tech-
nique in which the treated surface is run under a heated pressure roll,
pressing the coating into more intimate relationship with the substrate
without, however, impairing the character of the substrate. In this opera-
tion the calendering temperature and pressure conditions must be such as toavoid fusing the fibrils of the substrate.
T Havin Su er-H dro hobic Surfaces:
oys g p y p
Referring now to Figure 1, there is shown a molded maze 10 in ac-
cordance with the invention having an entrance 11 and a home base 12 which
communicates with the entrance through a circuitous path forming a pattern
of passagesor channels. These channels are defined by passage walls 13
projecting above a ground plate 14. The path is complicated by many blind
alleys, so that it is difficult to find the way to home base 12.
Instead of using a solid ball or other element to traverse the
winding path of the maze, the molded walls and ground plate of the maze
- 10 -
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which constitute a substrate are coated with a super-hydrophobic material
of the type previously described, and a large drop of water is introduced
at the entrance, the drop being converted by the surface into a water-ball
15. This ball may be directed through the passages by tilting the maze in
various ways to direct the ball into selected passages in order to reach
home base.
As shown in Figure 2, the channels are given a V-shaped configura-
tion. As a consequence of internal light reflection in the water ball
against the inclined walls 13 of the channels, mirror-like or silvery ef-
fects are produced which cause the water-ball to glitter or sparkel. Pig-
ment may be added to the water to enhance the attractiveness of the water-
ball.
In the game shown in Figure 3, a pin-ball type playboard 16 is
used with various obstacles, such as deflectors 17 and 18 on the board to
deflect the water-balls. However, instead of solid balls as in conventional
pin-ball machines, drops of water are introduced into the shooting chamber
19 associated with a spring-actuated retractable plunger 20. When the plun-
ger is released, it propels the water balls into the play area, the balls
being deflected in various directions. The entire working surface of the
pin-ball machine is coated with supe~hydrophobic material of the type pre-
viously disclosed so that the water-balls retain their ball-like integrity,
even though on impact with a given obstacle, the large ball may be dissected
into a multiplicity of small water-balls.
In order to effect scoring by means of electrically-actuated
lights and digits and other effects common to pin-ball machines, electrical
contact pairs 21, 22, 23 are disposed at various points on the board. Each
pair is connected to an electronic relay to actuate the appropriate indi-
cators or display elements when the pair is bridged by a water-ball.
To provide a shunt path when a pair of contacts is bridged by a
water-ball, the water used may include salt in solution or other substances
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enhancing the conductivity of the water. Or use may be made of a high-
impedance electronic relay, such as a Darlington amplifier which is rendered
operative when a relatively low resistance water path bridges the associ-
ated pair of contacts.
In the slide arrangement shown in Figures 4 and 5, a travel toy 24
in simulated vehicular form is adapted to slide on an inclined tracking 25.
The undersurface of toy 24 which engages the track is formed of hydrophilic
material and is made wet before use so that a thin film of water 24A is
formed thereon. The track 25 is coated with a layer of hydrophobic material
25A which repels the water film on the vehicle to create minute air cushions
thereon, whereby the toy, which may be in sled or in any other fanciful form,
effectively floats on the roadway and the sliding resistance thereto is vir-
tually nil.
As a consequence, the slightest applied force or the force of
gravity causes the vehicle to travel at high speed for long distances
limited only by the length of the toy track. Or one could, by means of a
retractable, spring-biased plunger, shoot a wet ball or other missile having
a hydrophilic surface along a treated track of this type.
Another version (not shown) of a hydrophilic/hydrophobic play de-
vice is a movable element in arrow form whose undersurface is hydrophilicand wetted so that it slides freely on the super-hydrophobic surface of a
board having numbers, words, letters or other symbols printed thereon, so
that the arrow effectively floats on the board. The position of the arrow
is manipulated by the player by slightly tilting the board so that the arrow
skims across the board until it comes to rest at a particular number, word
or symbol.
As will be evident, the passage walls 13 in Figure 1, the deflec-
tors 17 and 18 in ~igure 3, and the side walls of the track 25 in Figure 4,
all constitute guide means that constrain movement of a body on the super-
hydrophobic surface.
While there have been shown and described preferred embodiments
of toys and games using super-hydrophobic surfaces in accordance with the
invention, it will be appreciated that many changes and modifications may
be made therein without, however, departing from the essential spirit there-
of.
