Patent Application
20110203515
The present application is based on and claims the priority of Canadian provisional patent application serial number 2,691,554 entitled “Crystal Growing Device,” by Michael Krautter, filed Feb. 1, 2010, and is incorporated by reference herein.
The present invention is related to science and education toys and kits, and particularly to crystal growing toys and kits.
The symmetry and elegance of crystals holds a timeless appeal. Mineral crystals have been valued as jewels throughout recorded history, and even common crystals are appreciated for their beauty and used for decoration. Although natural crystals can take millennia to form, crystal growing kits allow people to produce crystals over the course of just days or weeks. Children and adults alike find the process of growing crystals themselves fascinating and thrilling.
An exemplary crystal growing kit is Kristal Educational's “Space Age Crystal Growing Kit, Set #641.” The method taught by this kit is to create a solution using a specified amount of a chemical and a specified amount of water. The water is boiled, mixed with the chemical, and stirred until the chemical is completely dissolved in the water to create a water/chemical solution. Rocks or stones are put at the bottom of the solution, the solution is allowed to cool until it is lukewarm, and then seed crystals are added to the solution. It is suggested that the seed crystals be put on top of the rocks. A lid is put on the container with the solution, and the container is put “in a place where it will not be disturbed by movement.” Visible crystals will start to form in a few hours, and the system should not be “disturbed for three or four days.” It should be noted that the instruction to not disturb or agitate the solution is also repeated elsewhere in the kit's instructions. After three or four days the crystals that have grown may be removed from the solution, or the lid may be taken off the container to allow evaporation, producing further crystal growth.
Because crystal nucleation is not avoided in the process taught by the Kristal Educational's “Space Age Crystal Growing Set,” there is a substantial amount of crystallization in the container other than on the main crystal cluster. The kit therefore suggests the additional steps of taking the excess solution and crystals which formed at the top of the solution or at the base of the main crystal cluster, mixing them together, heating it to boiling and stirring to dissolve all the chemical in the mixture, and pouring the heated mixture over the crystal cluster, and allowing further time for the dissolved chemical to crystalize to further increase the size of the crystal cluster.
Other crystal growing kits currently on the market, including: the Smithsonian “Crystal Growing Set—Series 1,” manufactured for the Smithsonian Institution by Natural Science Industries, Ltd. of West Hempstead, N.Y.; Toys 'R Us “Eduscience Crystal Growing Kit”; “Glowing Crystals” manufactured by Thames & Kosmos of Providence, R.I., United States of America; KOSMOS “Kristalle Zuechten,” manufactured by KOSMOS Verlag of Stuttgart Germany; and “Tree of Knowledge Crystal Wonder Crystal Growing Kit” manufactured by Elenco of Wheeling, Ill., United States of America, use essentially the same procedures as Kristal Educational's “Space Age Crystal Growing Set,” which is the original crystal growing set in the toy market. More particularly, all the crystal growing kits currently on the market teach using the chemicals used with Kristal Educational's “Space Age Crystal Growing Set,” creating a solution using boiling water, and not disturbing the solution during the crystal growth. The chemicals and procedures used in Kristal Educational's “Crystal Growing Set,” were written by Kristal Educational's founder, Heinz Juergen Teige, in 1978 in an article entitled “Kristalle Selber Zuechten,” which was published in conjunction with the 1979 Nuernberg Spielzeug Messe (Nuremberg Toy Show). It should also be noted that none of the prior art crystal growing kits teach controlled cooling, much less slow controlled cooling from the saturation temperature to reduce, inhibit, minimize or prevent crystal nucleation. Furthermore, none of the prior art crystal kits use semi-active cooling by monitoring the temperature and balancing ambient heat loss with computer controlled heating. Furthermore, none of the prior art crystal growing kits use of agitation to reduce, inhibit, prevent or minimize crystal nucleation. None of the prior art crystal growing kits are computer controlled or programmable. None of the prior art crystal growing kits include lighting to signal temperature stages or crystal growth stages or user actions. None of the prior art crystal growing kits take advantage of a saturation temperature at an intermediate point in the solubility curve where a substantial amount of chemical is dissolved so as to produce large crystals, yet the slope of the solubility curve is not so large that overly demanding temperature precision is needed to avoid, prevent, inhibit or minimize crystal nucleation in the solution. None of the prior art crystal growing kits make use of a specialized crystal growing apparatus and/or a specialized crystal growing container. And none of the crystal growing kits use different chemicals but in ratios that provide the same saturation temperature to provide the advantage of simplifying the apparatus and process.
It is therefore an object of the present invention to provide a method and apparatus for rapid crystal growth.
It is furthermore an object of the present invention to provide a method and apparatus for rapid crystal growth and/or for the growth of a large crystal (or crystals) which is reproducible and/or easy and/or safe for young children.
It is another object of the present invention to provide a method and apparatus for a crystal growth which is controlled by software.
It is another object of the present invention to provide a method and apparatus for crystal growth which is programmable.
It is another object of the present invention to provide a method and apparatus for a crystal growth for education purposes.
It is another object of the present invention to provide a method and apparatus for a crystal growth for use by children and/or laymen.
It is another object of the present invention to provide a method and apparatus for crystal growth which promotes crystal growth on a seed crystal while reducing, inhibiting, minimizing, or preventing crystal nucleation in the surrounding liquid.
It is another object of the present invention to provide a method for crystal growth in an apparatus where heat loss to the ambient environment is not easily calculable and/or is a significant factor in the temperature control process.
It is another object of the present invention to provide a method and apparatus for crystal growth which signals temperature stages and/or crystal growth stages and/or user actions with lighting, such as colored and/or flashing lighting.
It is another object of the present invention to provide a method and apparatus for agitation of a solution to produce crystal growth.
It is another object of the present invention to provide a method for crystal growth from a chemical/liquid mixture having a saturation temperature high enough above the freezing temperature of the liquid that a substantial amount of the chemical is dissolved, yet not so close to the boiling temperature that uncertainties in temperature yield large uncertainties in the amount of chemical dissolved.
It is another object of the present invention to provide a method for crystal growth from a chemical/liquid mixture having a saturation temperature high enough above the freezing temperature of the liquid that a substantial amount of the chemical is dissolved, yet with a saturation temperature low enough that the slope of the solubility curve reduces the precision of temperature control required for growth of the seed crystal without producing crystal nucleation in the liquid.
It is another object of the present invention to provide a method and apparatus for crystal growth which provides a user with the choice of utilizing two or more chemicals, particularly where the temperature control process is such that the same saturation temperature is utilized for any of the chosen chemicals.
Additional objects and advantages of the invention will be set forth in the description which follows, and will be apparent from the description or may be learned from the practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the claims.
The present invention is directed to a method for growing a crystal from a solution of a chemical in a container by adding the chemical and a liquid to the container to provide a mixture having a saturation temperature due to the relative amounts of the chemical and liquid used, the saturation temperature being below the boiling temperature of the liquid. The mixture is heated to the saturation temperature to produce a solution of the chemical in the liquid, and a seed crystal is submerged in the solution. The solution is then cooled by monitoring the temperature of the solution and applying heat based on the current temperature to balance ambient heat loss to produce crystal growth on the seed crystal.
The present invention is directed to a method for growing a crystal from a solution of a chemical in a container by adding the chemical and a liquid to the container to provide a mixture having a saturation temperature due to the relative amounts of the chemical and liquid used, the saturation temperature being below the boiling temperature of the liquid. The mixture is agitated to produce a vortex and a seed crystal is situated in the vortex so that it does not contact the mixture. The mixture is heated to the saturation temperature to produce a solution of the chemical in the liquid and the vortex is allowed to collapse so that the solution contacts the seed crystal. The solution is then cooled by monitoring the temperature of the solution and applying heat based on the current temperature to balance ambient heat loss to produce crystal growth on the seed crystal.
The present invention is directed to a method for growing a crystal from a solution of a chemical. The chemical is selected from one of two chemicals. Regardless of which chemical is selected, the amount of the chemical added to the liquid provides a particular saturation temperature. The chemical/liquid mixture is heated to the saturation temperature to produce a solution of the chemical in the liquid, and a seed crystal is submerged in the solution. The solution is then cooled by monitoring the temperature of the solution and applying heat based on the current temperature to balance ambient heat loss to produce crystal growth on the seed crystal.
The present invention is also directed to an apparatus for crystal growth having a chamber for containment of a chemical/liquid mixture, a thermistor for monitoring the temperature of the mixture, a heating element for applying heat to the mixture, and an electronic processor receiving temperature information from the thermistor and controlling the heat applied by the heating element. The processor raises the temperature of the mixture to the saturation temperature to produce a solution, and induces controlled cooling of the solution by applying heating based on the monitored temperature provided by said thermistor to balance ambient heat loss.
The present invention is also directed to an apparatus for mixing contents of a container. The apparatus has a base with a seat for seating the container, and a drive motor which rotates a drive housing having an even number, which is at least four, of permanent magnets equidistant from the rotational center of the drive housing and having alternating polarities. The apparatus also has a stirrer in the container and having the same number of permanent magnets of alternating polarities equidistant from a rotational center of the stirrer which is aligned with the rotational center of the drive housing.
Additional goals and features of the invention will be more readily apparent to those skilled in the art from the following detailed description and appended claims when taken in conjunction with the drawings, in which like reference numbers represent corresponding parts throughout.
Shown in cross-section in
An exploded view of the stirrer/heating/thermistor/lighting assembly (2000) is also shown in
Attached to the main PCB board (2010) is a motor (2020). According to the preferred embodiment of the present invention the motor (2020) is a desktop computer cooling fan motor, and in particular according to the present invention the motor is a Fonson model DFDO612H. The housing of the motor (2020) has four downwards-projecting threaded rods (2021) and four upwards-projecting threaded rods (2022). The main PCB board (2010) has four holes (2019) through which the downwards-projecting rods (2021) pass, and the motor (2020) is secured to the main PCB board (2010) by four hex nuts (2018) which are screwed onto the threaded rods (2021). In place of the fan blades (not shown) which are generally driven by a computer fan motor, the motor (2020) drives an agitator drive housing (2030) made of polycarbonate plastic. The agitator drive housing (2030) has a lower cylindrical portion (2032), and an upper cylindrical portion (2034) having a diameter less than that of the lower cylindrical portion (2032). At the top end of the drive housing (2030) are four depressions (2031) into which are seated four permanent magnets (2035). The permanent magnets (2035) are oriented to have alternating polarities, e.g., south, north, south, north, facing upwards. Covering the magnets (2035) is a housing cover (2039) which is attached to the drive housing (2030) via four screws around the perimeter of the cover (2039).
A ring-shaped secondary PCB board (2040) has an inner diameter slightly greater than the outer diameter of the upper cylindrical portion (2034) of the agitator drive housing (2030), and the secondary PCB board (2040) encircles the upper cylindrical portion (2034) of the drive housing (2030). Mounted on the secondary PCB board (2040) are equally-spaced light-emitting diodes (LEDs) (2041) and a thermistor (2042). The thermistor (2042) is covered by a thermistor cap/heat sink (2043) which is pressure-fitted into a hole (2590) (see
As shown in
As shown in
The thermistor cap (2043) fits snugly in a hole (2590) through the top of the bottom plug (2500). The thermistor cap (2043) is made of anodized aluminum or stainless steel. When liquid (130) is in the chamber (220), the thermistor cap (2043) is in contact with the liquid and shields the thermistor (2042) from the liquid (130) in the chamber (220). Because the thermistor (2042) is located near the heating element (2070), the temperature it (2042) measures may be offset to some degree from the temperature of the bulk liquid/solution (130). According to the preferred embodiment, calibration measurements are taken at the various agitation levels to provide calibration adjustments between the temperature measured by the thermistor (2042) and the actual temperature in the bulk liquid/solution (130).
At the center of the top of the inner portion (2520) of the bottom plug is a threaded well (2525). A stirrer pivot (2080) has a downwards-extending threaded rod (2081) and conical pivot (2082). The threading of the well (2525) and the rod (2081) mate, and the stirrer pivot (2080) is screwed into the threaded well (2525). A magnetic stirrer housing (2090) is substantially cylindrical and at the center of its bottom surface there is a conical indent (2092) with a flare which is slightly larger than the flare of the conical pivot (2081), thereby allowing the stirrer housing (2090) to spin freely on the conical pivot (2082). The upper surface of the stirrer housing (2090) has four indents (2091), and in each of the indents (2091) is a permanent magnet (2095). The permanent magnets (2095) are oriented to have alternating polarities, e.g., north, south, north, south, facing downwards. The four permanent magnets (2095) are magnetically mated with the four permanent magnets (2035) in the agitator drive housing (2030). The four-fold symmetry of the permanent magnets (2095) and the permanent magnets (2035) provides a stable, sustained, magnetic mating at high angular velocities. According to the present invention, the number of magnetic poles in the drive housing (2030) and the stirrer (2098) is at least four. A lessor number of magnets cannot provide the same degree of stability in the magnetic engagement for rotation. For instance, a two-fold symmetry in the magnetic mating permits large angular offsets that result in vibrations, slippages and other irregularities and instabilities making it problematic and/or inefficient to reach high angular velocities. A hollow, capped cylindrical stirrer cover (2099) has a cylindrical interior contour which provides a friction fit with the exterior contour of the stirrer housing (2090). The interior of the stirrer cover (2099) is coated with a foil metal shield (not visible) to shield the liquid/solution (130) from the magnetic fields of the permanent magnets (2095) so that the magnetic fields of the permanent magnets (2095) do not interfere with any ions or magnetic particles in the solution (130). (In an alternate embodiment the stirrer cover is a spherical section. The lack of edges of a spherical section provides the advantage of creating less turbulence and higher rotational velocities can be applied without the stirrer cover creating a whirlpool in the liquid/solution (130).) The stirrer housing (2090), permanent magnets (2095), and stirrer cover (2099) forms the stirrer (or rotor) (2098) which is rotatable to agitate the liquid/solution (130).
It should be noted that because crystal nucleation can occur throughout the liquid (although, as discussed herein, the method and apparatus of the present invention attempt to minimize the amount and/or likelihood of crystallization other than on the main crystal), the standard construction for a magnetic stirrer where the rotor spins on a cylindrical axle is problematic because of the large surface area of contacting, sliding surfaces. Crystal nucleation between the cylindrical axle and the surrounding cylindrical shaft will increase the sliding friction, possibly to the point where the rotor cannot rotate. The conical pivot (2082) of the present invention provides the advantage of reducing the contact area to essentially a point. Crystals which nucleate at the point of contact between the apex of the conical pivot (2082) and the apex of the conical indent (2092) can move away from the point of contact, and small or even moderate amounts of crystal nucleation do not impede the rotation of the stirrer housing (2090).
The present invention is directed to a means for crystal growth where the heat loss is a significant factor in the temperature control process. It should be noted that heat is lost from the chamber (220) to the ambient environment predominantly through the walls of the polycarbonate chamber tube (220). Less heat is lost through the polycarbonate plug (2500) at the bottom of the chamber (220), and the tube interface (225), screw cap (235), and top cap (210) at the top of the chamber (220). (According to an alternate preferred embodiment, the insulation provided by the chamber tube (220) could be increased by, for instance, substituting a double-walled construction.)
The main menu (6000) for the computer interface of the present invention is shown in
A flowchart of the crystal growth method (600) of the present invention is provided in
The cell is then tested (617) by calling an error check routine, ERROR_CHECK, which checks an error check variable, ERROR_CHECKSUM$. The error check variable ERROR_CHECKSUM$ must have a value of seven if the process (600) is to proceed. The value of ERROR_CHECKSUM$ is initialized with a value of zero, and the value of ERROR_CHECKSUM$ is incremented by unity if a USB cable is connected to the USB port (2011), the value of ERROR_CHECKSUM$ is incremented by unity if there is a signal from the microprocessor (2019) to the computer, the value of ERROR_CHECKSUM$ is incremented by unity if power consumption by the LEDs (2041) is confirmed, the value of ERROR_CHECKSUM$ is incremented by unity if power consumption by the motor (2020) is confirmed, the value of ERROR_CHECKSUM$ is incremented by unity if the thermistor (2042) senses a change in temperature due to heating by the heating resistors (2060), the value of ERROR_CHECKSUM$ is incremented by unity if the user has indicated that the chamber (220) is closed and sealed (or in an alternate embodiment, if contacts at the top of the chamber (220) indicate that the chamber (220) is closed and sealed). In an alternate preferred embodiment, the value of ERROR_CHECKSUM$ is further incremented by unity if the current through the solution resulting from the application of a known voltage indicates a resistance consistent with the presence of the allowed chemicals for use with the device (100) in the proper concentrations, e.g., pure water or an empty container will not provide the proper resistance. If ERROR_CHECKSUM$ does not (621) have a value of seven, then the errors which cause the value of ERROR_CHECKSUM$ to be less than seven are displayed and the process (600) returns to the main menu (6000). However, if ERROR_CHECKSUM$ does (622) have a value of seven, then the message, “User Input: Please choose the crystal growing chemical. Options: MAP, ALUM or IMPORT” is displayed (625). The variable MAT$ is then defined to be either “MAP” (626), “IMPORT” (627) or “ALUM” (628), depending on the input provided by the user.
According to the preferred embodiment of the present invention, the crystal growing chemicals to be used with the apparatus include ammonium phosphate monobasic (MAP), which has the chemical formula NH4H2PO4, and potassium aluminum sulfate (alum), which has the chemical formula KAl(SO4)2. The solubility of MAP as a function of temperature is shown in
The user message, “User instruction: Fill Cell with Chemical MAT$” is then displayed (630), where MAT$ has been defined as MAP or ALUM or the material specified upon importing information. Then the user message, “User Input: Are you done?” is displayed (635). If (636) the user is not done or if the user enters “No,” then the process (600) does not proceed. If (637) the user enters “Yes,” then the user message, “User Message: Please fill Cell with water” is displayed (638) until the user indicates (639) that this has been performed (by clicking on a “next” button, or the like). Then the user message, “User Input: Is the Cell filled with enough water?” is displayed (640). If (641) the user answers “No” or there is no response from the user, the process (600) does not proceed. However, if (642) the user answers “Yes,” the user message, “User Message: Please close the Cell and screw it shut” is displayed (643). Then the user message, “User Input: Is the Cell closed properly now?” is displayed (650). If (651) the user answers “No” or there is no response from the user, the process (600) does not proceed. However, if (652) the user answers “Yes,” a cell testing procedure, ERROR_CHECK, is called (653). As before, ERROR_CHECKSUM$ must have a value of seven if the process (600) is to proceed. If ERROR_CHECKSUM$ does not (661) have a value of seven, then the errors which cause the value of ERROR_CHECKSUM$ to be less than seven are displayed and the process (600) returns to the main menu (6000). However, if ERROR_CHECKSUM$ does (662) have a value of seven, then the message, “User Message: Starting crystal growing sequence now. Cell is heating to 37 degrees C. Please wait . . . ” is displayed (663).
The process (600) now enters preliminary heating control stage (665), which is time region (710) in
When (672) the temperature exceeds 37° C., the message “User Message: Cell has reached 37 degrees C. Cell will now heat to 47 degrees C. Please wait . . . ” is displayed (673). The process (600) now enters the intermediate heating control stage (674), which is time region (720) in
According to the present invention, the method (600) and device (100) are designed so that the user can select from multiple chemical/liquid mixtures to be used for the crystal growth and essentially the same saturation temperature is used for whichever mixture is chosen. This simplifies the control process (600) since there is just one process and essentially a single temperature profile. This also allows the design of the mechanical aspects of the device (100) to be simplified and optimized for the single range of temperatures. The most sensitive and crucial period in the process of the present invention for producing large crystals is the cooling at the beginning of the growth of the crystal, which starts at the saturation temperature and proceeds downwards. Preferably, the saturation temperatures of all the chemical/liquid mixtures are with 3° C., more preferably 2° C., still more preferably 1° C., still more preferably 0.5° C., still more preferably 0.3° C., and still more preferably 0.1° C. The device of the present invention uses semi-active heating control, i.e., there is a heater but no active cooling. Cooling is due to the loss of heat to the environment. The construction of the device (100) is complex and so heat loss is a complicated function which may vary considerably with both the ambient and internal temperature. Factors to be considered for a theoretical modeling include the expansion and contraction of the various components and the resulting varying degrees of thermal contact between the components. Heat loss as a function of temperature can most easily be found empirically. With crystallization beginning at the same temperature for each chemical, as per the method of the present invention, optimization of the control processes which provide cooling by balancing heat loss to the environment with heating by the heating element (2060) is facilitated.
As described in more detail below, according to the present invention, the saturation temperature is chosen to be far enough above ambient temperature that enough of the chemical is dissolved to provide a large crystal, yet the peak temperature and saturation temperature are not so high that (i) a large uncertainty in the amount of dissolved chemical is produced, (ii) the slope of the saturation curve is so great that it is difficult to achieve sufficiently precise temperature control to grow the crystal without producing crystal nucleation in the liquid, and/or (iii) the temperatures provide a significant danger to the user. The power input (2012) to the cell (100) is a 12 Volt input which draws 30 Watts or less. Ambient temperature, i.e., room temperature, is generally around 21° C. The temperature at which proteins denature is about 60° C. (although extended exposure to temperatures as low as 48° C. can cause denaturing), so 60° C. is the temperature at which the heat of the device (100) and the contained solution (130) becomes significantly dangerous.
The process (600) now enters the final heating control stage (679), which is time region (730) in
The process (600) now enters the initial cooling control stage (684), which is time region (740) in
In the temperature stasis stage (693), which is region (750) in
During the temperature stasis stage (693)/(750), the user message, “User Message: Cell has reached 49 degrees C. This is the seeding temperature. Open Cell top & unscrew plug. Attach seed to plug inside. Screw plug with seed back into Cell. Close Cell tightly.” is displayed (694). The user then removes the o-ring (255) from the end of the seed crystal chamber (253), inserts a seed crystal (237) into the chamber (253) of the seed crystal holder (250), replaces the o-ring (255) at the end of the seed crystal chamber (250), screws the threaded top (251) of the seed crystal holder (250) into the threaded well (234) at the bottom of the screw cap (235), and screws the screw cap (235) back into the tube interface (225). The seed crystal (237) may be a single crystal of the chemical or may be a tablet of the compressed powered chemical. When the user has inserted the seed crystal (237), the user indicates that the seed crystal (237) has been inserted by clicking on a “next” button (not shown).
Because the stasis temperature, 49° C., of this period (693)/(750) is greater than the saturation temperature, the seed crystal (237) will vanish if the user takes too long to proceed with the process (600). However, the seed crystal (237) is of a large enough size that the user has several minutes to insert the seed crystal (237) into the liquid (130) and reseal the chamber (220). (According to an alternate preferred embodiment, during this period (750) the stirrer housing (2090) is rotated at an extremely high level, i.e., in the neighborhood of 1000 rpm, so that a hollow is created at the center of the top of the liquid (130) by the resulting whirlpool. This gives the user more time to insert the seed crystal (237) and close the chamber (120) since the seed crystal (237) will not dissolve in the liquid (130) since it (237) is not touching the liquid (130).)
Then the user message, “User Question: Are you sure the Cell is well closed?” is displayed (6010). If the user answers “No” (6011) or if there is no response, then the user message, “User Message: Close Cell or abort experiment” is displayed (6013). If the user answers yes (6012), the user message, “User Message: The Cell will now grow the seed larger. This will take several hours/days. Please wait . . . ” is displayed (6015), and the apparatus (100) enters the crystal growing phase (760).
In the crystal growing phase (760) the crystal growth parameters (6016) are that the yellow LEDs (2041) are lit, the heating resistors (2060) are controlled as described below, the motor (2020) of the agitator is on at a low level, and the temperature is monitored by the thermistor (2042). The seed crystal (237) initially has a small surface area, so only a small amount of material can crystalize on the seed crystal (237) per unit time, and a rapid drop in temperature is to be avoided since it would produce crystal nucleation in the liquid (130). However, as the seed crystal (237) increases in size the amount which can be deposited on the seed crystal (237) increases, so the temperature can be decreased more rapidly without producing nucleation. According to the present invention, the temperature is controlled to drop off slowly at the beginning, increase to a maximum level, and then asymptote to room temperature, i.e., the temperature curve has an initial concave downwards portion (761), an intermediate, constant slope portion (762), and a subsequent concave upwards portion (763). According to the preferred embodiment of the present invention, monitoring of the temperature and controlled heating is applied to balance heat loss to the ambient environment so the temperature drops by 0.1° C. the first hour, 0.2° C. the second hour, 0.3° C. the third hour, 0.4° C. the fourth hour, and 0.5° C. the fifth hour and subsequent hours until the temperature becomes so close to the ambient temperature that a drop by 0.5° C. per hour is not possible since the apparatus does not include an active cooling mechanism.
Maintaining the agitation at the low level with the magnetic stirrer housing (2090) rotating at 20 to 30 rpm, and more preferably at 25 rpm, creates fluid flow within the liquid (130) which inhibits crystal nucleation until the temperature drops substantially below the saturation temperature. Within roughly 20 to 30 minutes, growth of the seed crystal (237) is visible. The entire crystal growing stage (760) takes between 12 and 72 hours and produces a crystal or crystal cluster of roughly 8 cm in diameter. It should be noted that any heating applied to slow the cooling due to ambient heat loss acts to also reduce the amount of crystal nucleation in the solution (130). It should be noted that any heating applied to slow the cooling due to ambient heat loss acts to also reduce the amount of crystal nucleation in the solution (130). Generally, the slower the crystal growth is induced, the clearer the crystal because less dislocations in the crystal structure result.
During the crystal growing stage (6016)/(760), the user has the option (not shown in
The temperature change is monitored (6020) at regular intervals as a function of time during the crystal growing stage (6016)/(760), and if the change in temperature is not (6021) less than 1° C. in 200 minutes, then the process (600) stays in the crystal growing phase (6016)/(760). However, when the change in temperature is (6022) less than 1° C. in 200 minutes, then the contents of the chamber (120) has reached a temperature close to the ambient temperature and semi-active cooling cannot be used to reduce the temperature substantially further to produce further crystal growth. The user message, “User Message: The Cell has completed the crystal growth” is then displayed (6024) until the user acknowledges by clicking (not shown) an acknowledgement button. Then the message, “User input: Are you satisfied with the result?” is displayed (6030). If the user replies that he/she is not (6031) satisfied, then the message, “User Input: Do you want to dissolve this crystal and restart the experiment with a new seed crystal?” is displayed (6035). If the user responds that he/she does (6037) wish to restart the experiment, then there is a return (6039) to the testing step (615) of the process (600). If the user responds that he/she does not (6036) wish to restart the experiment, then there is a return (6038) to the main menu (6000).
If, when the user is queried (6030) as to whether he/she is satisfied with the result, the user responds affirmatively (6032), then the LEDs (2041) are powered (6040), the user message, “User Message: You can now open the Cell's top screw plug and either remove the crystal carefully, or you can leave the crystal inside the Cell and use it as a night light and add some sparkles” is displayed (6045), and there is a return (6050) to the main menu (6000). According to an alternate embodiment of the present invention, the LEDs (2041) are synced to an audio data signal, as is well-known in the art musical/entertainment lighting, so the audio data signal causes flashing of the LEDs (2041).
A flowchart of the crystal growth method (1600) according to an alternate preferred embodiment of the present invention where a whirlpool (190) is created by the stirrer (2098) during initial stages of the process (1600) to prevent the solution (130) from contacting the seed crystal (237) is provided in
The cell is then tested (1617) by calling an error check routine, ERROR_CHECK, which checks an error check variable, ERROR_CHECKSUM$. The error check variable ERROR_CHECKSUM$ must have a value of seven if the process (1600) is to proceed. The value of ERROR_CHECKSUM$ is initialized with a value of zero, and the value of ERROR_CHECKSUM$ is incremented by unity if a USB cable is connected to the USB port (2011), the value of ERROR_CHECKSUM$ is incremented by unity if there is a signal from the microprocessor (2019) to the computer, the value of ERROR_CHECKSUM$ is incremented by unity if power consumption by the LEDs (2041) is confirmed, the value of ERROR_CHECKSUM$ is incremented by unity if power consumption by the motor (2020) is confirmed, the value of ERROR_CHECKSUM$ is incremented by unity if the thermistor (2042) senses a change in temperature due to heating by the heating resistors (2060), the value of ERROR_CHECKSUM$ is incremented by unity if the user has indicated that the chamber (220) is closed and sealed (or in an alternate embodiment, if contacts at the top of the chamber (220) indicate that the chamber (220) is closed and sealed). In an alternate preferred embodiment, the value of ERROR_CHECKSUM$ is further incremented by unity if the current through the solution resulting from the application of a known voltage indicates a resistance consistent with the presence of the allowed chemicals for use with the device (100) in the proper concentrations, e.g., pure water or an empty container will not provide the proper resistance. If ERROR_CHECKSUM$ does not (1621) have a value of seven, then the errors which cause the value of ERROR_CHECKSUM$ to be less than seven are displayed and the process (1600) returns to the main menu (6000). However, if ERROR_CHECKSUM$ does (1622) have a value of seven, then the message, “User Input: Please choose the crystal growing chemical. Options: MAP, ALUM or IMPORT” is displayed (625). The variable MAT$ is then defined to be either “MAP” (1626), “IMPORT” (1627) or “ALUM” (1628), depending on the input provided by the user.
The user message, “User instruction: Fill Cell with Chemical MAT$” is then displayed (1630), where MAT$ has been defined as MAP or ALUM or the material specified upon importing information. Then the user message, “User Input: Are you done?” is displayed (1635). If (1636) the user is not done or if the user enters “No,” then the process (1600) does not proceed. If (1637) the user enters “Yes,” then the user message, “User Message: Please fill Cell with water” is displayed (1638) until the user indicates (1639) that this has been performed (by clicking on a “next” button, or the like). Then the user message, “User Input: Is the Cell filled with enough water?” is displayed (1640). If (1641) the user answers “No” or there is no response from the user, the process (1600) does not proceed. However, if (1642) the user answers “Yes,” then the user message, “User Message: Load seed with seed” is displayed (1643).
The user loads the seed crystal (237) into the seed crystal chamber (253) and retains the seed crystal (237) within the chamber (253) by inserting the o-ring (255) into the end of the chamber (253), as described above. After the user hits a confirmation button (1644), the user message, “User message: Screw seeder into top lid” is displayed (1645). The user then screws the threaded top (251) of the seed holder (250) into the threaded well (234) of the cap (235). After the user hits a confirmation button (1646), the user message, “User message: Please close the Cell and screw it shut” is displayed (1648). The user then screws the cap (235) into the tube interface (225) and hits a confirmation button (not shown). Then the user message, “User Input: Is the Cell closed properly now?” is displayed (1650). If (1651) the user answers “No” or there is no response from the user, the process (1600) does not proceed. However, if (1652) the user answers “Yes,” a cell testing procedure, ERROR_CHECK, is called (1653). As before, ERROR_CHECKSUM$ must have a value of seven if the process (1600) is to proceed. If ERROR_CHECKSUM$ does not (1661) have a value of seven, then the errors which cause the value of ERROR_CHECKSUM$ to be less than seven are displayed and the process (1600) returns to the main menu (6000). However, if ERROR_CHECKSUM$ does (1662) have a value of seven, then the message, “User Message: Starting crystal growing sequence now. Cell is heating to 37 degrees C. Please wait . . . ” is displayed (1663).
The agitator motor (2020) is then turned on (1655) at the very high level, creating a vortex (190) at the top center of the chemical/liquid mixture (130). The chamber (253) of the seed holder (250) is located inside the vortex (190), as is shown in
When (1672) the temperature exceeds 37° C., the message “User Message: Cell has reached 37 degrees C. Cell will now heat to 47 degrees C. Please wait . . . ” is displayed (1673). The process (1600) now enters the intermediate heating control stage (1674), which is time region (1720) in
As described above for the process (600) of
The process (1600) now enters the final heating control stage (1679), which is time region (1730) in
The process (1600) now enters the initial cooling control stage (1684), which is time region (1740) in
At the beginning of the crystal growing phase (1760), the user message, “User Message: The Cell will now grow the seed larger. This will take several hours/days. Please wait . . . ” is displayed (8015). In the crystal growing phase (1760) the crystal growth parameters (8016) are that the yellow LEDs (2041) are lit, the heating resistors (2060) are controlled as described below, the motor (2020) of the agitator is on at a low level, and the temperature is monitored by the thermistor (2042). When the agitator level goes from very high to low, the vortex (190) collapses and the solution (130) comes into contact with the seed crystal (237) in the seed crystal chamber (253).
The seed crystal (237) initially has a small surface area, so only a small amount of material can crystalize on the seed crystal (237) per unit time, and a rapid drop in temperature is to be avoided since it would produce crystal nucleation in the liquid (130). However, as the seed crystal (237) increases in size the amount which can be deposited on the seed crystal (237) increases, so the temperature can be decreased more rapidly without producing nucleation. According to the present invention, the temperature is controlled to drop off slowly at the beginning, increase to a maximum level, and then asymptote to room temperature, i.e., the temperature curve has an initial concave downwards portion (1761), an intermediate, constant slope portion (1762), and a subsequent concave upwards portion (1763). According to the preferred embodiment of the present invention, monitoring of the temperature and controlled heating is applied to balance heat loss to the ambient environment so the temperature drops by 0.1° C. the first hour, 0.2° C. the second hour, 0.3° C. the third hour, 0.4° C. the fourth hour, and 0.5° C. the fifth hour and subsequent hours until the temperature becomes so close to the ambient temperature that a drop by 0.5° C. per hour is not possible since the apparatus does not include an active cooling mechanism.
Maintaining the agitation at the low level with the magnetic stirrer housing (2090) rotating at 20 to 30 rpm, and more preferably at 25 rpm, creates fluid flow within the liquid (130) which inhibits crystal nucleation until the temperature drops substantially below the saturation temperature. Within roughly 20 to 30 minutes, growth of the seed crystal (237) is visible. The entire crystal growing stage (1760) takes between 12 and 72 hours and produces a crystal or crystal cluster of roughly 8 cm in diameter. Generally, the slower the crystal growth is induced, the clearer the crystal because less dislocations in the crystal structure result.
During the crystal growing stage (8016)/(1760), the user has the option (not shown in
The temperature change is monitored (8020) at regular intervals as a function of time during the crystal growing stage (8016)/(1760), and if the change in temperature is not (8021) less than 1° C. in 200 minutes, then the process (1600) stays in the crystal growing phase (8016)/(1760). However, when the change in temperature is (8022) less than 1° C. in 200 minutes, then the contents of the chamber (120) has reached a temperature close to the ambient temperature and semi-active cooling cannot be used to reduce the temperature substantially further to produce further crystal growth. The user message, “User Message: The Cell has completed the crystal growth” is then displayed (8024) until the user acknowledges by clicking (not shown) an acknowledgement button. Then the message, “User input: Are you satisfied with the result?” is displayed (8030). If the user replies that he/she is not (8031) satisfied, then the message, “User Input: Do you want to dissolve this crystal and restart the experiment with a new seed crystal?” is displayed (8035). If the user responds that he/she does (8037) wish to restart the experiment, then there is a return (8039) to the testing step (1615) of the process (1600). If the user responds that he/she does not (8036) wish to restart the experiment, then there is a return (8038) to the main menu (6000).
If, when the user is queried (8030) as to whether he/she is satisfied with the result, the user responds affirmatively (8032), then the LEDs (2041) are powered (8040), the user message, “User Message: You can now open the Cell's top screw plug and either remove the crystal carefully, or you can leave the crystal inside the Cell and use it as a night light and add some sparkles” is displayed (8045), and there is a return (8050) to the main menu (6000). According to an alternate embodiment of the present invention, the LEDs (2041) are synced to an audio data signal, as is well-known in the art musical/entertainment lighting, so the audio data signal causes flashing of the LEDs (2041).
The solubility curve (900) for ammonium phosphate monobasic (MAP) in water is shown in
S=7×10−5 T3+0.0008 T2+0.6915 T+22.554. (eq. 1)
At slightly above freezing, i.e., 0° C., about 22.5 grams of MAP is soluble in 100 grams of water, at 21° C. about 40 grams of MAP is soluble in 100 grams of water, at 47.5° C. about 65 grams of MAP is soluble in 100 grams of water, and near the boiling temperature of water, i.e., 100° C., about 170 grams of MAP is soluble in 100 grams of water. (It should be noted that the polynomial of the above equation is an approximation to the solubility curve and experimentally it is found that roughly 174 grams of MAP is soluble in 100 grams of water. In general, there will always be differences between an experimentally derived solubility curve and a functional approximation to data points from the solubility curve.)
The solubility curve (950) for potassium aluminum sulfate, or alum, in water is shown in
S=0.0002 T3−0.0097 T2+0.5587 T+4.9514. (eq. 2)
At slightly above freezing i.e., 0° C., about 5 grams of alum is soluble in 100 grams of water, at 21° C. about 15 grams of alum is soluble in 100 grams of water, at 47.5° C. about 31 grams of alum is soluble in 100 grams of water, and near the boiling temperature of water, i.e., 100° C., about 163 grams of alum is soluble in 100 grams of water. (It should be noted that although the graph shows data to 80° C. and the melting temperature of alum is 92° C.—at which point the issue becomes liquid-liquid “miscibility” rather than liquid-solid “solubility”—the curve of
Larger crystals can be grown by increasing the amount of the chemical dissolved in the liquid. This is accomplished by increasing the amount of the chemical added to the liquid and increasing the temperature to which the mixture is heated as per the solubility curves (900) and (950) of
S=aT3+bT2+cT+d, (eq. 3)
i.e., a cubic polynomial, the relationship between the uncertainty ΔS in solubility and the uncertainty ΔT in temperature is
ΔS=ΔT(3aT2+2bT+c). (eq. 4)
Therefore, for low temperatures, ΔS≈ΔT, i.e., the uncertainty ΔS in solubility is linearly related to the uncertainty ΔT in temperature. However, for high temperatures, ΔS≈3aT2ΔT, i.e., the uncertainty ΔS in solubility increases as the square of temperature T.
To avoid nucleation in the solution (130) during the crystal growth stage (6016)/(760), the temperature drop per unit time, dT/dt, must be slow enough to allow the amount of chemical coming out of solution to add to the crystal seed (237). For a drop in temperature δT in a solution of volume V, the amount of chemical which comes out of solution is V(dS/dT)δT. The rate that the chemical can form as crystal on the crystal seed (237) is proportional to the density of chemical molecules in the solution, i.e., S, and the surface area of the crystal seed (237), i.e., 4π R2, where R is the characteristic radius of the crystal seed (237) at whatever stage of its growth it is at. So to avoid crystal nucleation in the solution (130),
dS/dT*dT/dt˜ƒ(T)SR2, (eq. 5)
where ƒ(T) is a function of the temperature which reflects the kinetics of the molecular bonding in crystal formation. This shows that a smaller decline in temperature per unit time, dT/dt, is required if the slope of the solubility curve, dS/dT, is large. Furthermore, as the crystal increases in size, i.e., as the characteristic radius R increases, the decline in temperature per unit time, dT/dt, may be increased.
Rather than attempting to maximize the amount of chemical dissolved in the liquid by having a high saturation temperature, according to the present invention less taxing demands are placed on the temperature control, which means less taxing demands are placed on: the temperature monitoring provided by the thermistor (2042), the control of the heating produced by heating resistors (2060), the software control provided by the microprocessor (2015), and the knowledge/understanding of the heat insulation provided by the crystal growth cell (100). According to the present invention, an amount of chemical is used which is large enough to produce a large crystal, but produces a saturation temperature at which the slope dS/dT of the solubility curve is not too large. The slope of the solubility curves (900) and (950) is least at the freezing temperature, 0° C., of water and greatest at the boiling temperature, 100° C., and that is generally the case for most solids soluble in a liquid. According to the preferred embodiment of the present invention, the saturation temperature TS is chosen to be at a temperature where the slope of the solubility curve is less than the average of the slope of the solubility curve at the freezing temperature Tf and the slope of the solubility curve at the boiling temperature Tb, i.e.,
where c=1. More preferably c=0.75, still more preferably c=0.5, still more preferably c=0.3, and still more preferably c=0.2.
where c=1. More preferably c=0.75, still more preferably c=0.5, still more preferably c=0.3, and still more preferably c=0.2.
However, because large crystals are desired, the saturation temperature TS for the liquid/chemical mixture should not be too close to the freezing temperature Tf so a substantial amount of the chemical is dissolved. According to the present invention the saturation temperature TS is chosen to be high enough that terms of higher order than linear in the solubility curve (900)/(950) begin to contribute so the slope at the saturation temperature TS is somewhat greater than that at the freezing temperature Tf. More specifically, according to the present invention
where preferably 1.25≦k≦2.5, more preferably 1.5≦k≦2.0, more preferably 1.65≦k≦1.85, still more preferably 1.7≦k≦1.8, and still more preferably k≈1.75.
As mentioned above in the description of the process (600) of the preferred embodiment of the present invention and shown in the temperature profiles (700) and (1700) of
Thus, it will be seen that the improvements presented herein are consistent with the objects of the invention for a method and apparatus for crystal growing. While the above description contains many specificities, these should not be construed as limitations on the scope of the invention, but rather as exemplifications of preferred embodiments thereof. Many other variations are also within the scope of the present invention. For example: aspects of the cell may have various other different constructions—for instance, the cap and base may be a single integrally-formed piece, other motors may be used, etc.; the device may not include a seed crystal holder; the components may be situated differently—for instance, the stirrer may be at the top of the chamber; other chemicals may be used; only a single chemical may be used; the crystals may be grown in a liquid other than water; a single large crystal rather than a crystal cluster may be grown; active cooling may be used; the chamber may have better insulation, such as a double-walled construction possibly enclosing a vacuum; the chamber may have a sensor to sense when the chamber is properly sealed; the device may not include an agitator; agitation may not begin until the crystal formation stage; the chamber tube may be coated with an infra-red heating foil to provide heating for the chamber; electrical contacts to the liquid, which may for instance be the thermistor cap and the heating element, may be used to monitor the conductivity of the liquid to insure that the correct liquid and/or the correct chemicals and/or the correct ratios are utilized; the components may be made of other materials—for instance, the heating element may be glass or stainless steel or a Teflon-coated material, plastics other than polycarbonate plastic may be used, materials other than anodized aluminum, such as stainless steel, may be used, etc.; active cooling may be used, for instance via the Peltier thermoelectric effect; the method and apparatus may be adapted for other uses, such as tissue growth or acrylics production; the apparatus may be used with gases or gels; pressure may be manipulated to induce transformations such as dissolving and crystallization; the seed crystal can be encapsulated in a gel or some other dissolvable material to give the user more time to insert the seed crystal in the liquid, and allow more flexibility in the temperature control and greater repeatability; the seed crystal may be inserted into the liquid using a mechanism, possibly an automated mechanism, that would circumvent the need to open the container; the seed crystal may be located at the bottom of the chamber; the seed crystal may be attached to the seed crystal holder in another fashion, such as gluing; the system may be powered solely by power from the USB input; a different saturation temperature may be used; heating may not be applied to hold the temperature constant during the stage when the seed crystal is inserted into the solution; the cooling curve for crystal growth may be different—for instance, a constant rate of cooling, such as 0.5° C. per hour, may be used; no heat may be applied during the crystal growth stage; no agitation may be used during any or all of the process stages; different rates of agitation may be used during any or all of the process stages; the temperature curve during the crystal growth stage may have a different shape—for instance, there may not be a constant slope portion; other variables may be included or variables may be excluded from the error check; etc.
Furthermore, the description of the physical principles underlying the operation and performance of the present invention are described as presently understood, but may include approximations, simplifications and assumptions and are not intended to be limiting. For example: a solubility curve may be approximated by a different function, such as a polynomial of a higher or lower degree; least squares or other fits may be used to find a functional approximation to the solubility curve; the solubility curve may differ from the functional approximation to the solubility curve, and the difference may be greater at the high temperature end, the low temperature end, or in an intermediate region; a solubility curve may have portions which are not concave upwards; agitation of the mixture may have effects other than those described or contrary to or counteracting those described; the heating or semi-active cooling may be different from that shown during any of the heating or cooling stages, including the crystal growth stage; the pH may be altered to affect the solubility; crystal growth may have a different dependence on temperature, time, or the solubility curve; etc.
Accordingly, it is intended that the scope of the invention be determined not by the embodiments illustrated or the physical analyses motivating the illustrated embodiments, but rather by the appended claims and their legal equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2691554 | Feb 2010 | CA | national |
