Patent Publication Number: US-8121016-B2

Title: Rotation responsive disk activation and deactivation mechanisms

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is related to, claims the earliest available effective filing date(s) from (e.g., claims earliest available priority dates for other than provisional patent applications; claims benefits under 35 USC §119(e) for provisional patent applications), and incorporates by reference in its entirety all subject matter of the following listed application(s) (the “Related Applications”) to the extent such subject matter is not inconsistent herewith; the present application also claims the earliest available effective filing date(s) from, and also incorporates by reference in its entirety all subject matter of any and all parent, grandparent, great-grandparent, etc. applications of the Related Application(s) to the extent such subject matter is not inconsistent herewith. The United States Patent Office (USPTO) has published a notice to the effect that the USPTO&#39;s computer programs require that patent applicants reference both a serial number and indicate whether an application is a continuation or continuation in part. The present applicant entity has provided below a specific reference to the application(s) from which priority is being claimed as recited by statute. Applicant entity understands that the statute is unambiguous in its specific reference language and does not require either a serial number or any characterization such as “continuation” or “continuation-in-part.” Notwithstanding the foregoing, applicant entity understands that the USPTO&#39;s computer programs have certain data entry requirements, and hence applicant entity is designating the present application as a continuation in part of its parent applications, but expressly points out that such designations are not to be construed in any way as any type of commentary and/or admission as to whether or not the present application contains any new matter in addition to the matter of its parent application(s). 
     RELATED APPLICATIONS 
     
         
         1. For purposes of the USPTO extra-statutory requirements, the present application constitutes a continuation in part of currently co-pending United States patent Application entitled METHOD AND SYSTEM FOR FLUID MEDIATED DISK ACTIVATION AND DEACTIVATION, naming Bran Ferren, Eleanor V. Goodall, and Edward K. Y. Jung as inventors, U.S. application Ser. No. 11/124,924, filed May 9, 2005. 
         2. For purposes of the USPTO extra-statutory requirements, the present Application constitutes a continuation in part of currently co-pending United States patent Application entitled FLUID MEDIATED DISK ACTIVATION AND DEACTIVATION MECHANISMS, naming Bran Ferren, Eleanor V. Goodall, and Edward K. Y. Jung as inventors, U.S. Ser. No. 11/504,547, filed Aug. 14, 2006, which is a continuation in part of United States patent application entitled FLUID MEDIATED DISK ACTIVATION AND DEACTIVATION MECHANISMS, naming Bran Ferren, Eleanor V. Goodall, and Edward K. Y. Jung as inventors, U.S. Ser. No. 11/124,923, filed May 9, 2005, now U.S. Pat. No. 7,519,980 issued on Apr. 14, 2009. 
         3. For purposes of the USPTO extra-statutory requirements, the present application constitutes a continuation in part of currently co-pending United States patent Application entitled METHOD AND SYSTEM FOR ROTATIONAL CONTROL OF DATA STORAGE DEVICES, naming Bran Ferren, Edward K. Y. Jung, and Clarence T. Tegreene as inventors, U.S. Ser. No. 11/150,837, filed Jun. 9, 2005. 
         4. For purposes of the USPTO extra-statutory requirements, the present application constitutes a continuation in part of currently co-pending United States patent Application entitled ROTATION RESPONSIVE DISK ACTIVATION AND DEACTIVATION MECHANISMS, naming Bran Ferren, Edward K. Y. Jung, and Clarence T. Tegreene as inventors, U.S. Ser. No. 11/150,823, filed Jun. 9, 2005 now U.S. Pat. No. 7,668,068. 
         5. For purposes of the USPTO extra-statutory requirements, the present application constitutes a continuation in part of currently co-pending United States patent application entitled FLUID MEDIATED DISK ACTIVATION AND DEACTIVATION MECHANISMS, naming Bran Ferren, Eleanor V. Goodall, and Edward K. Y. Jung as inventors, U.S. Ser. No. 11/998,850, filed Nov. 29, 2007, which is a continuation in part of United States patent Application entitled FLUID MEDIATED DISK ACTIVATION AND DEACTIVATION MECHANISMS, naming Bran Ferren, Eleanor V. Goodall, and Edward K. Y. Jung as inventors, U.S. Ser. No. 11/124,923, filed May 9, 2005, now U.S. Pat. No. 7,519,980 issued on Apr. 14, 2009. 
       
    
    
    
     TECHNICAL FIELD 
     The present application relates, in general, to the control of access to information stored on memory or data storage devices. In particular, it relates to control of access to information through modification of data storage media. 
     BACKGROUND 
     Various methods have been used to control access to information stored on data storage devices such as CDs, DVDs, floppy disks, and so forth. Methods of controlling access to information are utilized for various reasons including, for example, to limit unauthorized access to copyrighted information. Such methods may involve requiring the use of access codes provided, e.g., on data storage device packaging in order to read information from a data storage device, or erasing data or preventing reading of data from a data storage device following reading of the device. 
     SUMMARY 
     Embodiments of methods and systems for fluid mediated regulation of access to information on data storage devices are disclosed. Features of various embodiments will be apparent from the following detailed description and associated drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Features of the invention are set forth in the appended claims. The exemplary embodiments may best be understood by making reference to the following description taken in conjunction with the accompanying drawings. In the figures, like referenced numerals identify like elements. 
         FIG. 1  illustrates a system including a disk drive; 
         FIG. 2  illustrates a computer system; 
         FIG. 3  illustrates parameters relating to rotation of a disk; 
         FIGS. 4A-4C  illustrate angular velocity, its derivative, and its square, respectively; 
         FIG. 5  depicts a disk having a rotation activated fluid release mechanism; 
         FIG. 6  depicts fluid release devices configured to release fluid in response to angular acceleration or deceleration; 
         FIGS. 7A and 7B  depict a fluid release mechanism; 
         FIG. 8  illustrates a disk having machine readable data stored thereon; 
         FIG. 9  illustrates a disk having machine readable data stored thereon; 
         FIG. 10  illustrates a capillary valve mechanism; 
         FIG. 11  illustrates a further valve mechanism; 
         FIG. 12  illustrates a microvalve; 
         FIGS. 13A and 13B  illustrate degradation of a portion of a data storage medium produced by introduction of a fluid; 
         FIGS. 14A and 14B  illustrate degradation of data produced by introduction of a fluid; 
         FIGS. 15A and 15B  depict blocking of reading of data by a fluid; 
         FIGS. 16A and 16B  illustrate degradation of a portion of a data storage medium produced by release of a fluid; 
         FIGS. 17A and 17B  illustrate degradation of data produced by release of a fluid; 
         FIGS. 18A and 18B  illustrate optical interference with data reading produced by release of a fluid; 
         FIGS. 19A and 19B  depict degradation of a portion of a data storage medium produced by a fluid acting in combination with an additional degradation inducing factor; 
         FIGS. 20A and 20B  depict degradation of data produced by a fluid acting in combination with an additional degradation inducing factor; 
         FIGS. 21A and 21B  depict a fluid blocking degradation of data by an additional degradation inducing factor; 
         FIG. 22  depicts a disk having a rotation activated fluid release mechanism; 
         FIG. 23A-23C  illustrate exemplary patterns of angular velocity, its derivative, and its square, respectively; 
         FIG. 24A-24C  illustrate exemplary patterns of angular velocity, its derivative, and its square, respectively; 
         FIG. 25  illustrates a data storage device having a plurality of centrifugally activated fluid release mechanisms; 
         FIGS. 26A and 26B  depict an embodiment of a fluid switch; 
         FIGS. 27A and 27B  depict another embodiment of a fluid switch; 
         FIGS. 28A and 28B  illustrate blocking of reading of data by closing a switch; 
         FIGS. 29A and 29B  illustrate producing destruction of data by closing a switch; 
         FIGS. 30A and 30B  illustrate producing modification of data by closing a switch; 
         FIG. 31  illustrates a data storage device with a fluid release mechanism activatable over multiple uses; 
         FIGS. 32A and 32B  depict a rotation activatable switch; 
         FIG. 33  illustrates different orientations of rotation activatable switches; 
         FIG. 34  is a schematic diagram of a system including a data storage device; 
         FIG. 35  is a flow diagram of a method of activating a rotation activatable control mechanism in association with reading data; 
         FIG. 36  is a flow diagram of a method of activating a rotation activatable control mechanism in association with reading data; 
         FIG. 37  is a flow diagram of a method of activating a rotation activatable control mechanism in association with reading data; 
         FIG. 38  is a flow diagram of a method of activating a rotation activatable barrier in association with reading data; 
         FIG. 39  is a flow diagram of a method of controlling access to data on a disk; 
         FIG. 40  is a flow diagram of a method of controlling access to data on a disk; 
         FIG. 41  is a flow diagram of a method of manufacturing a data storage device; 
         FIG. 42  is a flow diagram of a method of operating a disk drive; 
         FIG. 43  is a flow diagram of a method of configuring a disk drive for use with a rotation-sensitive disk; 
         FIG. 44  depicts a data storage device with a rotation activatable switch mechanism; 
         FIG. 45  depicts a data storage device including four rotation activatable switch mechanisms; 
         FIGS. 46A and 46B  illustrate a data storage device with a rotation-responsive barrier portion; 
         FIGS. 47A and 47B  illustrate a data storage device with a rotation-responsive evaporating degradation barrier; 
         FIGS. 48A and 48B  illustrate a data storage device with a rotation-modifiable barrier portion; and 
         FIG. 49  is a flow diagram of a method of manufacturing a data storage device. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a system  10 , which may be a computer system or other system that includes a data storage device  24  configured for rotating access. System  10  includes a processor  12 , system memory  14 , one or more I/O devices  16 , and disk drive  22 , which is configured to receive a disk shaped data storage device  24 . The system may also include a power supply, not shown. Data, power and control signals may be transferred between system components via data bus  26 . Processor  12  may be a microprocessor. In this example, and in general, data storage device  24  may be a CD, DVD, floppy disk, or any of various other data storage devices configured for rotating access. Such data storage devices are frequently disk shaped, but the invention is not limited to use with disk shaped data storage devices. 
     As a specific example of the system depicted in  FIG. 1 ,  FIG. 2  illustrates a computer system  28 . Computer system  28  includes a processor  12 , system memory  14 , system bus  26 , output device  32 , which in this example is a monitor, and input device  34 , which in this example is a keyboard. System memory  14  includes read-only memory  36  and random-access memory  38 . Device driver  40  is stored in random-access memory  38 . Device driver  40  is used to control disc drive  30 . Interface  42  provides an interface between the computer system  28  and disk drive  30 . Control line  60  and data line  62  provide for the transfer of control and data signals between system  28  and disk drive  30 . Disk drive  30  includes receptacle  56 , which is adapted to receive disk  24 . Disc  24  is rotated by motor  46 . Positioner  48  adjusts the position of the read head  50  with respect to disk  24 . 
       FIG. 3  illustrates parameters associated with rotation of disk  24 , which may be a disk shaped data storage device  24 . Disk  24  may have a radius r. If disk  24  is rotated with angular velocity ω, for example in a counterclockwise direction as depicted in  FIG. 3 , a particle at the periphery of the disc will move with a tangential velocity V T . The centripetal acceleration a c  indicated by the grey arrow, will be ω 2 r.  FIGS. 4A-4C  depict the relationship between angular velocity, ω, and dω/dt and ω 2 , which are proportional to angular acceleration, and centripetal acceleration, respectively. Values of ω, dω/dt and ω 2  depicted in  FIGS. 4A-4C  are obtained when a disk that is initially at rest is rotated, increasing the rate of rotation over a first time period  76  until a constant angular velocity is reached, then held at a constant angular velocity for a second time period  78 , and then gradually brought to rest again over a third time period  80 . This is only one example of many possible disk rotation patterns. In  FIG. 4A , the angular velocity ω, represented by trace  70 , is increased from zero over first time period  76  of duration t 1  until a velocity ω 1  is reached, held constant at velocity ω 1  over second time period  78  having a duration t 2 , and then decelerated back to zero angular velocity over third time period  80 , also of duration t 1 . The corresponding angular acceleration, dω/dt, represented by trace  72  in  FIG. 4B , has a value of ω 1 /t 1  during first time period  76  and a value of −ω 1 /t 1  during third time period  80 , and is otherwise zero. The centripetal acceleration experienced by a particle at a given location on the disk will be equal to square of the angular velocity multiplied by the distance of the location from the center of rotation. Thus, for a particle at the periphery (at a distance r from the center of rotation), the centripetal acceleration will be ω 2 r. Trace  74  in  FIG. 4C  represents ω 2 , which is proportional to the centripetal acceleration. As can be seen in  FIG. 4C , ω 2  increases non-linearly over first time period  76 , is constant during second time period  78 , and decreases non-linearly over third time period  80 . As a disk rotates, a particle (which may be fluid or liquid) in or on the disk will experience an apparent “centrifugal force”, proportional to the centripetal acceleration and operating in the opposite direction, driving the particle toward the periphery of the disk. During periods of angular acceleration and deceleration (e.g., time periods  76  and  78  in  FIGS. 4A-4C ), a particle in or on the disk will experience an angular force proportional to the angular acceleration dω/dt and of the same sign, with the direction of the angular force depending on whether the disk is accelerating or decelerating. 
       FIG. 5  depicts an embodiment of a disk  100  having a rotation activated fluid release mechanism  101 . Fluid release mechanism  101  may include fluid chamber  102 . Fluid chamber  102  may contain a degradation inducing fluid  104 , which is retained in chamber  102  by pressure sensitive fluid barrier  106 . A degradation sensitive region  110  located within a chamber  108  may be located radially outward of fluid chamber  102 . When disk  100  is rotated, centrifugal force F C , indicated by a black arrow, moves fluid  104  toward fluid barrier  106 . The fluid release mechanism in  FIG. 5  is sensitive to centripetal acceleration (‘centrifugal force’). 
     Changing the orientation of the fluid release mechanism, can make the mechanism sensitive to forces associated with angular acceleration, or deceleration. Such a device may be obtained, for example, by orienting a fluid release mechanisms  122  and  124  on disk  120  as depicted in  FIG. 6 . A positive angular velocity ω, is obtained when the direction of rotation of disk  120  is as indicated by the gray arrow. Angular acceleration will produce inertial force F A  in fluid in fluid release mechanism  122 , in the direction indicated by the black arrow. Angular deceleration will produce inertial force F D  in fluid release mechanism  122 , in the direction indicated by the black arrow. Thus, fluid will be released from fluid release mechanism  122  during angular acceleration of sufficient magnitude, and fluid will be released from fluid release mechanism  124  during angular deceleration of sufficient magnitude. 
     As depicted in  FIG. 7A , F C , drives fluid  104  against fluid barrier  106  to produce a pressure differential across fluid barrier  106 , such that the pressure P 1  on the radially inward side of fluid barrier  106  (i.e., the side toward fluid chamber  102 ) is higher than the pressure P 0  on the radially outward side of fluid barrier  106  (i.e., the side toward degradation sensitive region  110 ). Air vents  112  and  114  may be included to permit the movement of fluid within chamber  102  and  108 . When the pressure differential becomes large enough, fluid barrier  106  may rupture, break down, or otherwise release fluid  104  so that it moves into chamber  108 , where it may cause degradation of degradation sensitive region  110 .  FIG. 7B  depicts the fluid barrier in ruptured form  106 ′. In this example, fluid barrier  106  is a frangible fluid barrier. Pressure sufficient to permit movement of fluid from the reservoir may be obtained by spinning the substrate. If an optical disk is used, in some embodiments pressure sufficient to permit movement of fluid may be obtained by spinning the substrate in an optical disk drive at normal read speeds, while in other embodiments, pressure across the pressure sensitive barrier sufficient to permit movement of fluid from the reservoir may be obtainable by spinning the substrate in an optical disk drive at speeds above normal read speeds. Similarly, if the data storage device is a magnetically readable disk, pressure across the pressure sensitive barrier sufficient to permit movement of fluid from the reservoir is obtainable by spinning the substrate in a magnetic disk drive at normal read speeds in some embodiments, while in other embodiments pressure across the pressure sensitive barrier sufficient to permit movement of fluid from the reservoir is obtainable by spinning the substrate in a magnetic disk drive at speeds above normal read speeds. 
     Machine readable data is commonly stored in a binary code, which may be stored in various materials that can exist in two different states. For example, data may be stored in a pattern of electrical potentials, magnetized regions, optically transmissive regions, or optically reflective regions, among others, as known or as may be devised by those of skill in the relevant arts. A degradation sensitive region of a data storage device may include any portion of the data storage device that may be modified in some way to render information stored in the region inaccessible or unusable in some way. ‘Degradation’ may include modification of data stored in a data storage medium. A first state in the data storage medium may represent a ‘1’, while a second state may represent a ‘0’. Various other coding schemes may be used, which may include more than two different states. Modification of data values may include setting all data values to a ‘1’, setting all data values to a ‘0’, resetting data values to a random value or to some pattern (e.g., alternating ‘1’s and ‘0’s), or reducing the signal-to-noise ratio of the stored data. Degradation may include destruction of the data storage medium so that no data may be stored therein. Degradation of a degradation sensitive region may include destruction or modification of a substrate or coating located adjacent or near a data storage medium. If data is read optically, with the use of light transmitted through a transparent substrate, reading of data may be blocked, for example, by modifying or degrading the substrate to block or hinder transmission of light through the substrate. 
     In some embodiments, degradation may affect all or most of the data stored on a disk, with degradation considered to include destruction or modification of data, destruction or modification of a data storage medium, or destruction or modification of a substrate or coating layer adjacent or near a data storage medium. In other embodiments, all or portions of data on a data storage device may be rendered inaccessible by degrading a subset of data on the data storage device that contains information necessary for reading data stored on other parts of the data storage device. For example, as depicted in  FIG. 8 , data of interest (which might be, for example, a computer program or an audio or video digital recording) may be distributed to multiple locations on data storage device  150 . In order to retrieve the data of interest in usable form, it may be read from the appropriate location in the appropriate order, as specified by index information stored in disk region  152 . In the present exemplary embodiment, disk region  152  may specify that data may be read from first data region  154 , second data region  156 , third data region  158 , fourth data region  160 , fifth data region  162  and sixth data region  164 , in that sequence. Thus, in order to render the data stored in first through sixth data regions  154  through  164  unusable, it may be sufficient to render data stored in disk region  152  inaccessible, for example by degradation of data, data storage medium, and/or substrate, as described above. 
     Various other methods of controlling access to data on a disk by causing degradation of a limited portion of the disk may also be used. Another example is depicted in  FIG. 9 . In  FIG. 9 , disk  170  includes data region  172  containing data of interest in encrypted form. Key region  174  contains a decryption key that may be used to decrypt data stored in data region  172 . Degradation of key region  174  may thus be sufficient to block access to data stored in data region  172 . 
     In some embodiments, an index or key portion of data may contain information necessary for reading data from other regions of the data storage device. Degradation of index or key data thus causes “deactivation” of the data storage device. In other embodiments, an index or key region may contain a code that blocks reading of data from the disk, e.g., because after the information has been read from the disk, reading is discontinued by the disk drive or program controlling reading of data from the disk. Degradation of such key or index information then “activates” or enables reading of data from the data storage device. As a further alternative, the key or index information may activate or deactivate selected portions of the data storage device, so that (for example) different data may be read from the data storage device on the first reading than on the subsequent readings. 
       FIGS. 5 ,  7 A and  7 B depict exemplary embodiments in which a pressure sensitive fluid barrier  106  is a frangible barrier. Various other barrier or valve structures that open in response to fluid pressure, including but not limited to capillary breaks, hydrophobic breaks, or hydrophobic valves, may also be used.  FIGS. 10 and 11  depict additional exemplary fluid barriers. In  FIG. 10 , a first chamber  200  and second chamber  202  are separated by a restricted diameter valve region  204 . Valve region  204  may be any of various types of passive or capillary valves, for example, as described in “Design and Fabrication of Polymer Microfluidic Platforms for Biomedical Applications,” Madou et al., ANTEC 2001, pp. 2534-2538; “Design Analysis of Capillary Burst Valves in Centrifugal Microfluidics,” Zeng et al., Tech. Proc. of μTAS, May 2000, Enschede, The Netherlands, pp. 493-496; U.S. Pat. No. 6,591,852 and U.S. Pat. No. 6,296,020, all of which are incorporated herein by reference in their entirety. Such valves may block the movement of fluid unless a sufficiently high pressure differential is applied across the restriction. In some embodiments, if an aqueous fluid is used, and chambers  200  and  202  and valve regions  204  may be formed in a hydrophobic material, an abrupt reduction in channel diameter, as occurs at entrance  206  of valve region  204 , may obstruct the flow of fluid. Alternatively, a capillary break, or channel widening, as at exit  208  of valve region  204  may function as a passive or capillary valve. As depicted in  FIG. 11 , a valve region  224  between chambers  220  and  222  may also be formed by the application of a surface treatment  226  to the interior of valve region  224 . For example, a hydrophobic surface treatment  226  may be used to obstruct the flow of an aqueous fluid through valve region  224 , while a hydrophilic surface treatment may obstruct the flow of a non-polar fluid through valve region  224 . Alternatively, surface treatment  226  may include a dried material that, when dissolved in the fluid, modifies the surface tension of the fluid. 
     Different types of microvalves may be used in various embodiments. In some embodiments, micromechanical valves may include elements that physically block a fluid channel, and are controllable by various means. Such micromechanical valves may include, for example colloidal or polymeric valve elements that can be moved or changed in size or configuration to open the valve. A few examples are described, for example in U.S. Pat. Nos. 6,837,476, 6,802,489, and 6,793,753, all of which are incorporated herein by reference in their entirety  FIG. 12  depicts in schematic form a fluid chamber  240  separated from a degradation sensitive region  242  by a microvalve  244 . 
     Degradation of data may take place by various mechanisms, and may include degradation or modification of data, data storage medium, and/or substrate. Degradation of the data storage medium may include one or more of destruction of the data storage medium, modification of the data storage medium, modification of data stored in the data storage medium, and modification of signal-to-noise ratio of data stored in the data storage medium. Degradation may take place directly in response to a degradation inducing influence, or it may be initiated by a degradation inducing influence but continue to completion after removal of the degradation inducing influence. This may be the case, for example, if the degradation inducing influence provides input of an activation energy sufficient to overcome an energetic barrier and set off a chemical process that proceeds without further input of energy once initiated. A degradation inducing influence may produce degradation directly, or may function as an intermediary to enable or initiate action by a direct degradation inducing influence. Degradation may include various combinations of two or more degradation mechanisms, and in some embodiments may be produced by synergistic or cooperative effects of two or more degradation inducing or producing factors or influences. In general, release of fluid may produce (directly or indirectly) a modification of a modifiable feature on a data storage device. Examples of modifiable features include, but are not limited to, mechanical properties, optical properties, electrical properties, magnetic properties, or chemical properties.  FIGS. 12-20  provide examples of a number of fluid-induced degradation mechanisms, caused by introduction of fluid into a region of a data storage device or removal of fluid from a region of a data storage device. In some embodiments, degradation may occur substantially simultaneously with introduction of fluid, e.g., substantially instant destruction of data may be obtained. 
     In  FIG. 13A , a portion of a data storage device  250  is depicted. Data storage device  250  includes a substrate  252  and a data storage medium  254  storing binary data  256 , represented by a pattern of black blocks representing one of two states of data storage medium  254 . A channel  258  runs through substrate  252 . Channel  258  is empty in  FIG. 13A . In  FIG. 13B , fluid  259  has filled channel  258 . The presence of fluid  259  causes degradation substrate  252  to form degraded substrate  252 ′, through which data  256  cannot be read. Degradation of substrate  252  may include a change in a material property of the substrate or a change in shape or conformation of the substrate material, such as thickness or surface texture. Material properties may include optical properties such as reflectivity, index of refraction, transmissivity, light scattering, electrical properties, magnetic properties, and so forth. Modifications to material properties, shape, or conformation may be caused by a phase change, chemical reaction, melting, etching, corrosion, etc. of the substrate material due to exposure to fluid. Many specific combinations of substrate material and degradation inducing fluid may be used; examples include the combination of water (or other aqueous fluids) with water-absorbing polymers that expand upon exposure to water; the combination of an oxidation-inducing fluid in combination with a substrate containing colorless compounds that may be oxidized to form colored compounds, such as indigo carmine, methylene blue, thionin, gallocyanine, among others, as discussed in U.S. Pat. No. 6,011,772, which is incorporated herein by reference. 
       FIGS. 14A and 14B  illustrate a portion of a data storage device  260 . Data storage device  260  includes a substrate  262  and a data storage medium  264  storing binary data  266 , again represented by a pattern of black blocks representing one of two states of data storage medium  264 . A channel  268  runs between substrate  262  and data storage medium  264 . Channel  268  is empty in  FIG. 14A . In  FIG. 14B , fluid  269  has filled channel  268 . The presence of fluid  269  causes degradation of data  266  stored in data storage medium  264 . Degraded data  266 ′ is readable but does not contain the correct information. Modification or destruction of data may be caused by a phase change or chemical produced in the data storage medium due to exposure to the degradation inducing fluid. For example, in optical disks, a reflective layer of metallic aluminum may be used as a data storage medium. Exposure of metallic aluminum to an aqueous salt solution, for example, may result in oxidation of the aluminum to form non-reflective hydroxy salts. 
       FIGS. 15A and 15B  illustrate a portion of a data storage device  270 , which includes a substrate  272 , data storage medium  274  containing data  276 , and fluid channel  278 . Data is read through substrate  272  and channel  278  when channel  278  is empty. Reading could be by various means, for example, optically, magnetically, electrically, and so forth. As shown in  FIG. 15B , when fluid  279 , which is opaque or non-transmissive to the read signal, fills channel  278 , reading of data through substrate  272  is blocked. Fluid  279  may absorb, reflect, scatter, or otherwise interfere with a signal used to read data  276 . Fluids may absorb, reflect, scatter, or otherwise be non-transmissive to electrical signals, optical signals, magnetic signals, or various other signals used to read data  176  from data storage medium  274 . Fluids that may be used to block optical reading of data include various dye solutions. Fluids containing ferric and/or ferrous materials may be used to block magnetic reading of data include. 
       FIGS. 16A and 16B  illustrate degradation of a region of a data storage device  280  produced by release of a fluid from the region. Data storage device  280  includes substrate  282 , data storage medium  284  containing data  286 , and channel  288  containing fluid  289 . Data  286  may be read through substrate  282  and fluid  289 . In  FIG. 16B , fluid  289  has been release from channel  288  so that it is empty (i.e., it fills with air that enters via an air channel when fluid  289  is released). In the absence of fluid  289 , the substrate degrades to degraded substrate  282 ′, which is non-transmissive to the read signal and thus prevents reading of data  286 . Substrate  282  may degrade when exposed to one or more components of air, or it may be an unstable material that is preserved by the presence of the fluid but degrades with the release of fluid from channel  288 . Possible combinations of substrate and fluid that exhibit these properties include substrates that include a colorless compound that is oxidized upon exposure to air to form a colored compound (e.g. methylene blue, thionin, indigo carmine, or gallocyanine) used in combination with an oxidation-protective fluid such as a buffer. 
     Similarly,  FIGS. 17A and 17B  illustrate degradation of data produced by release of a fluid from a region  290  of a data storage device. Fluid channel  298  is formed between substrate  292  and data storage medium  294 , which contains data  296 . Fluid  299  is contained in fluid channel  298 . In  FIG. 17B , fluid  299  has been released, leaving channel  298  empty. In the absence of fluid  299 , data  296  stored in data storage medium  294  is modified or degraded to degraded data  296 ′, which may be readable but does not contain usable information. Possible combinations of data storage medium and fluid that result in such a degradation pattern include metallic data storage media used in combination with an oxidation-protective fluid. 
       FIGS. 18A and 18B  illustrate optical interference with data reading produced by release of a fluid. In  FIG. 18A , portion  300  of a data storage device includes a substrate  302 , data storage medium  304  containing data  306 , and channel  308  containing fluid  309 . Fluid  309  may have an index of refraction that matches that of substrate  302 , to permit optical reading of data  306 . When fluid  309  is released from channel  308 , as depicted in  FIG. 18B , a mismatch between the index of refraction of substrate  302  and air contained in channel  308  may hinder reading of data  306 . 
     In  FIGS. 19A and 19B , a portion of data storage device  320  is depicted which includes substrate  322 , data storage medium  324 , and channel  328  between substrate  322  and data storage medium  324 . Data storage medium  324  contains data  326 . Data storage device  320  is exposed to an additional degradation inducing factor or influence  330 , which may be, for example, heat, light, other forms of electromagnetic radiation, pressure, a magnetic field, or an electrical field. Additional degradation inducing factor  330  has no effect by itself, but, as depicted in  FIG. 19B , when fluid  329  is introduced into channel  328 , fluid  329  and additional degradation inducing factor  330  act synergistically or in cooperation to produce degradation of substrate  322  to degraded form  322 ′, to block reading of data  326 . Additional degradation inducing factor  330  may function to provide activation energy for a reaction involving fluid  329  and substrate  322 . For example, fluid  329  may contain a reactant that will participate in a reaction (e.g., a reduction or oxidation reaction) upon exposure to an additional degradation inducing factor as listed above to produce a change in color or dimension of substrate  322 . 
       FIGS. 20A and 20B  depict a portion of data storage device  340 , which includes substrate  342  and data storage medium  344 , which contains stored data  346  and has a channel  348  running through it. Data storage medium  344  is exposed to additional degradation inducing factor  350 . Additional degradation inducing factor  350  has no effect until, as in  FIG. 20B , fluid  352  is introduced into channel  348 . Additional degradation inducing factor  350  may be, for example, heat, light, other forms of electromagnetic radiation, pressure, a magnetic field, or an electrical field. Fluid  352  and additional degradation inducing factor  350  act in combination to produce degradation of data  346  to degraded form  346 ′. As discussed above, additional degradation inducing factor may provide activation energy to a chemical reaction between fluid  352  and data  346  stored in data storage medium  344 . 
     In another embodiment, a fluid may be released from a region of a data storage device to permit exposure of a degradation sensitive region to degradation by an additional degradation inducing factor. In  FIG. 21A , a portion of data storage device  360  includes substrate  362  and data storage medium  264  containing data  366 . Fluid  370  contained within channel  368  may block exposure of data storage medium  364  to degradation inducing factor  372 . As shown in  FIG. 21B , when fluid is released from channel  368 , data storage medium  364  is exposed to degradation inducing factor  372 , which converts data stored therein to a degraded form  366 ′. For example, degradation inducing factor  372  may be light, and fluid  370  may be a fluid that blocks transmission of light, examples of which are provided above. As an alternative, degradation inducing factor  372  may be a magnetic field, and fluid  370  may be a fluid that blocks or otherwise modifies transmission of the magnetic field, for example, a fluid containing ferrous and/or ferric materials. Various combinations of degradation inducing factors and blocking fluids may be designed for use in various embodiments, by a practitioner of skill in the relevant arts. 
     The specific type of fluid that may produce degradation of substrate, data storage medium, or data, as illustrated in the forgoing examples, will depend upon the materials used as substrate and data storage medium, and the method by which data is read. Fluids may have various chemical, optical, electrical, physical, thermal, and/or other properties selected to work in combination with data storage device materials, and, in some embodiments, with additional degradation inducing influences, to produce a desired effect. Similarly, the additional degradation inducing influence may be selected based upon choice of substrate, data storage medium, and fluid type. Exemplary combinations have been presented. Additional combinations will be apparent to the practitioner of skill in the art, and the foregoing examples are not intended to be limiting. As used herein, the term ‘fluid’ may include a variety of materials having fluid-like properties, including but not limited to liquids, gases, powders, and various combinations thereof. The term fluid encompasses both homogeneous and inhomogeneous materials or mixtures. Combinations may include emulsions, suspensions, and slurries. In some cases, the fluid may be a combination made up of a fluid or fluid-like carrier material and an active component carried in the carrier material. The carrier material may confer upon the mixture its fluid properties, while the active component may confer up on the fluid its degradation-inducing or degradation-preventing properties. 
     As noted previously, release of fluid may cause degradation or other modification of a disk immediately upon its release, or it may initiate a process which may take place over some period of time following initiation (by selecting the process appropriately, the process may take place over seconds, minutes, hours, days or weeks, depending upon the particular chemical processes involved). If degradation is not immediate, it may be satisfactory to initiate the degradation process before any data has been read from the disk, and any fluid release mechanism that is activated at some point during a read of data from the data storage medium may be sufficient. If, however, fluid release produces immediate data degradation when it enters the fluid sensitive or fluid responsive region of the data storage medium, then fluid release must be controlled in such a manner that it occurs only after data has been read from the data storage device. If the fluid causes degradation of only key or index data, then it may be acceptable or desirable to release fluid after key or index data has been read from the disk, but possibly prior to reading of data from other areas of the disk. In various embodiments, it may be desirable to control the timing of the release of fluid. 
       FIG. 22  is an exemplary embodiment of a data storage device configured such that fluid released in such a way that it enters a fluid responsive region following a single read of data from the device.  FIG. 22  depicts a data storage device  400  that includes a disk-shaped substrate configured for rotating access. Machine-readable data may be stored in a data storage medium carried by the substrate. The data storage device also includes a fluid release device and associated fluid circuit configured to deliver fluid to a portion of the data stored on the data storage device following a single use of the device. Data storage device  400  includes reservoir  404 , which is adapted to contain fluid  406 . Data storage device  400  also includes fluid responsive or fluid sensitive region  402 , which is configured to receive fluid from reservoir  404  and upon receipt of fluid to undergo a change, which may include any of various types of changes or modifications as depicted in the previous examples. A pressure sensitive barrier  408  between reservoir  404  and fluid responsive region  402  is adapted to prevent flow of fluid from reservoir  404  to fluid responsive regions  402  if the pressure drop across pressure sensitive barrier  408  is below a first pressure difference, and to permit flow of fluid from reservoir  404  to fluid responsive region  402  if the pressure drop exceeds the first pressure difference. First radial channel segment  410  extends radially outward from pressure sensitive barrier  408  and is adapted to receive fluid from reservoir  404 . Connecting channel segment  412  is adapted to receive fluid from first radial channel segment  410 . Second radial channel segment  414  extends radially inward from connecting channel segment  412  to fluid responsive region  402 , and is adapted to deliver fluid from connecting channel segment  412  to fluid responsive region  402 . 
     In use, fluid  406  moves from reservoir  404  when the centrifugal force is sufficient to cause barrier  408  to fail, and moves down first radial channel segment  410  to connecting channel segment  412 , driven by centrifugal forces. Fluid  406  may move into connecting channel segment  412  driven by angular acceleration forces, or may be drawn in by capillary forces. Fluid may move through second radial channel segment  414  to fluid responsive region  402  when centrifugal forces decrease to a level where they are surpassed by capillary forces in second radial channel segment  414  and fluid responsive region  402 . Centrifugal forces will initially reach the level needed to cause fluid to flow through pressure sensitive barrier  408  when the disk rotates as reading of the disk is initiated, and centrifugal forces may decrease sufficiently to allow fluid to flow into second radial channel segment  414  and to fluid responsive region  402  when the disk decelerates at the end of reading. 
     In some embodiments, the pattern of disk rotation that occurs during a single use or reading of a disk may not match the simple acceleration pattern depicted in  FIGS. 4A-4C , in which acceleration to a constant velocity is eventually followed by deceleration back to rest. If the disk is read in sequence, in some cases the angular velocity may be varied as a function of distance of the read head from the center of the disk, in order to provide a constant linear velocity at the position of the read head. Moreover, depending on how the data is distributed on the disk, reading may involve multiple accelerations and decelerations. For example, the angular velocity, ω, and corresponding dω/dt and ω 2 , may be as depicted in  FIGS. 23A-23C . In order to control the timing of fluid release with respect to reading of some or all of the data from the disk, the expected pattern of disk rotation during reading of the disk may be taken into account, the inertial forces due to angular and centripetal acceleration determined, and pressure sensitive barrier and fluid channels on the disk must be configured appropriately. The orientation and break pressure of each pressure sensitive barrier may be selected according to the anticipated rotation pattern, and capillary forces produced by fluid channels such as second radial channel segment  414  in  FIG. 22 , which may depend upon channel dimensions and combination of channel material and fluid properties, may be selected to operate in cooperation with inertial forces. 
       FIGS. 23A-23C  illustrate ω, and corresponding dω/dt and ω 2 , in a case where the data storage medium is driven by a motor that produces a constant torque, and hence constant acceleration or deceleration. As shown in  FIG. 23A , angular velocity ω, represented by trace  419 , increases linearly over time interval  422  to a first constant velocity at peak  424 . ω decreases linearly over time interval  426  to a second constant velocity  428 , increases again over time interval  430  to a third constant velocity,  432 , decreases over time interval  434  to fourth constant velocity  436 , and increases again over time interval  438  to reach fifth constant velocity  440 , which is the same as third constant velocity  432 . Finally, ω decreases over time interval  442  until the substrate is at rest. Corresponding values of dω/dt and ω 2  are indicated by traces  420  and  421  in  FIGS. 23B and 23C , respectively. It can be seen from  FIG. 23B  that over time intervals  422 ,  430 , and  438 , the angular acceleration dω/dt is of constant amplitude, but the duration of the acceleration pulses varies depending on the corresponding change in angular velocity. Similarly, over time intervals  426 ,  434 , and  442 , dω/dt is of constant negative amplitude, but the duration of the deceleration pulses varies depending on the corresponding change in angular velocity. The start of disk use could be detected, for example, by providing a fluid release mechanism that was sensitive to long-duration angular acceleration pulse  444 . Similarly, the end of disk use could be detected by providing a mechanism sensitive to long-duration angular deceleration pulse  446 . Centrifugal forces, proportional to ω 2 , may show peaks, e.g.,  446 ,  450 , and  458  as depicted in  FIG. 23C , that may be differentiated by duration-sensitive mechanisms, offering further possibility for controlling the timing of disk activation or deactivation. 
       FIGS. 24A-24C  depict a further pattern of angular velocity ω, indicated by trace  530  in  FIG. 24A . The corresponding pattern of angular acceleration dω/dt is indicated by trace  532  in  FIG. 24B , and the corresponding value of ω 2 , proportional to the associated “centrifugal force” is represented by trace  534  in  FIG. 24C . In the example of  FIGS. 24A-24C , the magnitude of angular acceleration dω/dt (and the associated inertial forces) is variable, so different segments of disk use may be characterized by differences in amplitude as well of duration in angular acceleration forces. Note that angular acceleration peaks  536  and  540  differ in both amplitude and duration; similarly, angular deceleration peaks  538  and  544  differ in amplitude and duration. Centrifugal forces, proportional to ω 2 , as indicated by trace  534  in  FIG. 24C , similarly show differences in amplitude and duration (e.g., peaks  546  and  548 ) that may be detected by appropriately configured fluid release devices. 
     In some embodiments, it may be desirable to produce activation of a fluid release mechanism at a particular time during a use of a data storage device. This can be accomplished easily in the case that angular acceleration only occurs at the beginning of each use, and angular deceleration occurs only at the end of each use (as depicted in  FIGS. 4A-4C ) by orienting fluid release devices so that they are sensitive to angular acceleration or deceleration, as desired. If multiple angular accelerations and decelerations occur during a single use, as depicted in  FIGS. 23A-23C  and  24 A- 24 C, then it may be possible to set a threshold value for response of a fluid release device to angular acceleration, so that fluid may be released during the highest acceleration condition that occurs during use of the data storage device. Similarly, a threshold value may be set for angular deceleration, so that fluid may be released during the highest deceleration condition that occurs during use of the data storage device. In some embodiments, amplitude of disk acceleration may not provide a sufficient basis for controlling timing of fluid release during use of the disk, but duration of acceleration may be used for identifying a time when fluid should be released. For example, if a constant torque motor is used, a long acceleration period will be necessary to bring the disk up to speed initially, and a long deceleration period will be necessary to bring the disk back to rest at the end of a use, but changes in speed during a single use may involve shorter periods of acceleration or deceleration. Therefore, the beginning and end of a single use may be identified through the use of a mechanism that is responsive to acceleration or deceleration, respectively, of a specified duration. Fluid valves that are sensitive to the duration of exposure to rotational forces may be used. 
     Another method for controlling timing of fluid release during use of a data storage device is to combine fluid release with exposure of a fluid-sensitive portion of the data storage device to an additional degradation inducing influence. Degradation inducing influence may include heat, light, other forms of electromagnetic radiation, pressure, a magnetic field, or an electrical field. The use of fluid release in combination with an additional degradation inducing factor is shown in  FIGS. 20A and 20B  or  FIGS. 21A and 21B . In these examples, degradation is produced by combining release of a fluid, which may occur at some point during a use of a device, with an additional factor. For example, if the additional factor is a beam of light from a read head, the disk may be configured so that the degradation sensitive region is located on a portion of the disk that is exposed to light from the read head only once during use of the device, e.g. at the end of use when the read head passes over the edge of the disk as it returns to its ‘parked’ position. Providing fluid is release at some time during use of the device, the degradation sensitive portion of the disk will respond when it is exposed to light, which occurs at a well-defined time during use of the disk. Accordingly, the degradation is produced or initiated at a well-defined time even if the timing of fluid release is not precisely controlled, but is known to happen at some point during use of the disk. 
     The previous exemplary embodiments are suitable for producing or initiating disk activation or deactivation by modifying a feature of a data storage device at some point during a single use of the device. However, in many cases it may be desirable to produce disk deactivation (or modify the availability of certain data on the disk) after multiple uses of the data storage device. For example, a demo disk may be useable for a fixed number of uses before it becomes unusable, or a rental DVD containing a movie may be useable for a limited number of viewings. 
       FIG. 25  depicts an exemplary data storage device that is configured for producing disk deactivation after a selected number of uses of the disk. One approach for detecting multiple uses of a data storage device (e.g., for the purpose of limiting access to the data storage device after a certain number of uses) is to provide methods for modifying the disk during normal use in such a way that structures on the disk that are modified by use are modified in sequence over multiple uses, rather than all being modified by a single use. This may be accomplished by setting different thresholds for the different structures, and driving the disk differently (e.g. at a higher speed) on each subsequent use.  FIG. 25  illustrates a data storage device  750  with a plurality of centrifugally activated fluid release devices  752 ,  754 ,  756 , and  758 , of the type depicted in  FIGS. 5 ,  6 A and  6 B. Fluid release device  752  includes fluid chamber  758  containing fluid  760 , fluid barrier  762 , and degradation sensitive region  764 . Similarly, fluid release device  754  includes fluid chamber  766  containing fluid  768 , fluid barrier  770 , and degradation sensitive region  772 , fluid release device  756  includes fluid chamber  774  containing fluid  776 , fluid barrier  778 , and degradation sensitive region  780 , and fluid release device  758  includes fluid chamber  782  containing fluid  784 , fluid barrier  786 , and degradation sensitive region  788 . Fluid release devices  752 ,  754 ,  756 , and  758  may be configured to be activated in sequence over a number of uses of data storage device  750 . This may be accomplished by various methods. In one embodiment, fluid barriers  762 ,  770 ,  778 , and  786  may be configured to break at different pressures. For example, the first fluid barrier may break at a rotation speed obtained during normal use of the device. On a subsequent use of the device, activation of the first fluid release device may be detected, and the drive may produce rotation a first above-normal speed of rotation for a period sufficient to activate a second fluid release device. Similarly, on each subsequent use of the device, activation of at least the most recently activated fluid release device may be detected, and following detection, the disk may be rotated at a speed of rotation sufficient to activate the next fluid release device. Thus, a selected number of uses of the device may be detected, until the maximum allowable number of uses has been reached, and the disk is deactivated. The device and methodology associated with  FIG. 25  may be carried out with the use of a modified disk drive or drive controller, in order to obtain higher rotations with each used of the disk. However, by appropriately configuring the rotation sensitive structures on the disk, the sensitivity of each structure to rotation may be modified by release of fluid by the preceding fluid release mechanism. Accordingly, modification of each structure other than the first is dependent upon prior modification of at least one other structure. Modification of a first structure may modify the sensitivity of another structure by various methods, for example, by releasing a fluid that dissolves a barrier to air or fluid movement, by opening or closing an electrical circuit to produce modification of an electrically sensitive fluid barrier (e.g., formed by an electroactive polymer, piezoelectric material, or MEMS structure). 
     A rotation activated fluid switch capable of opening or closing an electrical circuit can be constructed as depicted in  FIGS. 26A and 26B  and  27 A and  27 B. The fluid switch of  FIGS. 26A and 26B  is closed by release of fluid from a fluid chamber.  FIG. 26A  shows first chamber  500  containing an electrically conductive fluid  502 , which is retained in chamber  500  by barrier  504 . Also shown is second chamber  506 , which includes electrical contact  508  connected to lead  510 , and electrical contact  512  is connected to lead  514 . Second chamber  506  may initially be filled with air or with a non-conductive fluid. When fluid  502  is subjected to a force (e.g., a centrifugal force), it may break through barrier  504  (to form ruptured barrier  504 ′) and enter second chamber  506 . Air vents  520  and  522  may be required to permit fluid  502  to move from first chamber  500  to second chamber  506 . When fluid  502  fills second chamber  506 , fluid  502  forms an electrical connection between contact  508  and  512 , thus permitting the structure of  FIGS. 26A and 26B  to function as a switch. Leads  510  and  514  may be connected to various types of electronic circuitry. 
       FIGS. 27A and 27B  depict another embodiment of a fluid activated switch, similar to that depicted in  FIGS. 26A and 26B  except that release of fluid from the first chamber causes the switch to open rather than to close. In  FIG. 27A , a structure is provided which includes a first chamber  600  filled with conductive fluid  602 , and a barrier  604  that prevents the flow of fluid  602  into second chamber  614 . In this embodiment, electrical contact  606 , connected to lead  608 , and electrical contact  610 , connected to lead  612 , are located in first chamber  600 . Again, air channels  620  and  622  are provided to permit the flow of fluid from first chamber  602  to second chamber  614  when barrier  604 ′ is broken or ruptured, as depicted in  FIG. 26B . If fluid  602  is a conductive fluid, the electrical circuit (switch) between leads  608  and  612  is closed when fluid  602  is contained in first chamber  600 , and is opened when fluid  602  breaks through barrier  604  and moves into second chamber  614 . 
     Opening or closing of a switch (which may be a fluid switch or other type of switch) may be utilized in various ways to produce modification or degradation of data, or render data unreadable or otherwise inaccessible. Several methods are illustrated in  FIGS. 28A-28B , which are exemplary of a larger number of methods that may be used. 
       FIGS. 28A and 28B  illustrate blocking of reading of data by closing a switch. A system  650 , which is a portion of a data storage device such as an optically readable disk, is shown. The data storage device includes substrate layer  562  and data storage medium  654 , in which is stored binary data  656 . Data  656  may be read through substrate layer  652 , e.g., via light delivered and sensed by an optical read head. Region  658  of substrate layer  652  includes a voltage sensitive material. Lead  664  and lead  666  are connected to opposite sides regions of voltage sensitive region  658 . Voltage source  660  and switch  662  are connected in series between leads  664  and  666 . When switch  662  is open, region  658  of substrate  652  is in a state that permits optical reading of data  656 . When switch  662  is closed (with closed configuration indicated by  662 ′), however, as depicted in  FIG. 28B , voltage sensitive region  658  transforms to a different state, indicated by reference number  658 ′, through which data  656  cannot be read. Voltage sensitive region  658  may be formed, for example, from a liquid crystal or various other materials that are responsive to an applied voltage. Voltage source  660  may include any of a number of devices or structures that are capable of storing or generating electrical potentials. For example, piezoelectric structures on the disk may convert vibration or other motion in the disk to voltages. Alternatively, electrostatic charges may be accumulated on the rotating disk. Switch  662  may be a fluid switch as depicted in  FIGS. 24A-25B , or may be some other type of switch. 
       FIGS. 29A and 29B  illustrate degradation of data by closing a switch. In this example, a portion  670  of a data storage device is shown, which includes substrate layer  672  and data storage medium  674 , which contains data  676 . Leads  682  and  684  are connected to opposite sides of data storage medium  674 . Current source  678  and switch  680  are connected in series. Current source  678  may be any structure capable of generating an electric current or capable of having an electric current induced within it. For example, the disk may include circuitry (e.g., a conductive loop) for generating current on the disk by induction from magnetic fields produced by nearby structures, such as the drive servo motor. When the switch is in a closed state  680 ′, as shown in  FIG. 29B , current passes through data storage medium  674  to convert it to degraded state  674 ′, so that data  676  is lost. In this example, data storage medium  674 ′ has been converted to a state in which no data values are stored. 
     In other cases, data stored in a data storage medium may be modified, so that the data stored therein is readable, but does not contain meaningful or useful information. For example in  FIG. 30A , a portion  690  of a data storage medium is shown which includes substrate  692  and data storage medium  694  containing data  696 . Voltage source  698  and switch  700  are connected in series across data storage medium  694 , by means of leads  702  and  704 . When switch  700  is opened, as indicated in  FIG. 30B  by reference number  700 ′, data stored in data storage medium  694  is converted to modified data  696 ′. For example, data  696 , which included a pattern of logical ‘1’s and ‘0’s, may be converted to a pattern of all ‘1’s or all ‘0’s, as represented by the modified data  696 ′. 
     Fluid switches as depicted in  FIGS. 26A ,  26 B,  27 A and  27 B utilize fluid to open or close an electrical circuit. By replacing electrical contacts with light conductors, an optical fluid switch could be constructed, which might be used to control the exposure of a light sensitive data storage medium to light or control additional optical circuitry on the disk. 
     As discussed above, in some embodiments, it may be desirable to produce or initiate data degradation of substrate, data, or data storage medium only after a selected number of uses or reads of the disk have been performed. Various methods may be devised to track the number of times a disk or other data storage device has been used based on the state of the disk. In some embodiments, the disk drive may be controlled appropriately to activate a different fluid release device upon each use of the device. In other embodiments, the disk may include multiple structures that are activated in sequence over multiple uses of the device, where activation of each structure facilitates activation of the next structure. 
       FIG. 31  illustrates a data storage device  800  with a fluid switch that is activatable by multiple uses. In  FIG. 31 , fluid chamber  802  contains a conductive fluid  804  retained by barrier  806 . First outward channel segment  808  extends radially outward from fluid chamber  802  and leads to first distal channel segment  810 . First distal channel segment  810  connects to first inward channel segment  812 , which lead to first proximal channel segment  814 . During a first use of data storage device  800 , data storage device  800  is rotated at a velocity that produces a centrifugal force in fluid  804  sufficient to break barrier  806 , following which fluid  804  moves down first outward channel segment  808  to first distal channel segment  810 . Fluid  804  is retained in first distal channel segment  810  until rotation of data storage device  800  decreases sufficiently, at the end of the first use. Fluid  804  then moves through first inward channel segment  812  to first proximal channel segment  814 , where it resides until the next use of the device. Note that sizes and surface characteristics (hydrophilicity, hydrophobicity, etc.) of the various channel segments can be selected to promote desired movement of fluid in the channel segments, and that appropriate selection of channel dimensions and surface characteristics may generate capillary forces that act in cooperation with forces generated by rotation of data storage device  800 . During a second use of data storage device  800 , fluid moves from first proximal channel segment  814 , through second outward channel segment  816  to second distal channel segment  818 . At the end of the second use, fluid moves through second inward channel segment  820  to second proximal channel segment  822 , where it resides until the next use of the device. Finally, upon the third use of the device, fluid moves from second proximal channel segment  822 , through third outward channel segment  824 , and to third distal channel segment  826 . At the end of the third use, fluid moves through third inward channel segment  828  and into fluid chamber  830 . Fluid chamber  830  may include contacts  832  and  834 , to form a fluid switch as described previously in connection with  FIGS. 26A-26B  and  27 A- 27 B. It should be noted that the dimensions of the fluid chambers and channels depicted in  FIG. 31  are not exact, and that the actual dimensions of the fluid containing structures may be selected so that the entire fluid volume from fluid chamber  802  may be contained by each distal or proximal channel segment, and, eventually, fluid chamber  830 . When fluid fills fluid chamber  830  to close the fluid switch and form a closed circuit by connecting line  840  between electronic circuit components  836  and data storage region  838 ), electronic components  836  cause a modification of data storage region  838 . The modification may be any modification of data, data storage medium, or substrate, for example as described in connection with any of  FIGS. 28A-30B . In related embodiments, fluid chamber  830  may contain a degradation sensitive data storage medium that is degradable upon exposure to a degradation inducing fluid. 
     As an alternative to using rotationally activated, fluid-mediated mechanisms to produce modification to a data storage medium to render data unreadable or otherwise inaccessible, or to modify, destroy, or erase data, it may also be possible to use other types of rotationally activated mechanisms to produce modifications to a data storage device.  FIGS. 32A and 32B  depict a rotation activatable mechanical switch, including a cantilever made up of a beam  902  having at its end a mass  904 , within a chamber  906  formed in a substrate  908 . Electrical contact  910  is located in the wall of chamber  906  and connected to a lead  912 . Electrical contact  914  is formed on mass  904  and connected to lead  916 , which passes through beam  902 . When mass  904  is subjected to sufficient force, in the direction indicated by the arrow F in  FIG. 32B , beam  902  may flex, until contacts  910  and  914  touch to form an electrical connection between leads  912  and  916 . Leads  912  and  916  may be connected to various electronic circuit components, to produce modification of at least a portion of a data storage device, e.g., as described in connection with  FIGS. 28A-30B . The sensitivity of the mechanical switch, i.e., the amount of force required to close the switch, may be controlled by selecting the mass of mass  904  and stiffness of beam  902  appropriately. 
       FIG. 33  depicts different orientations of rotation activatable mechanical switches of the type depicted in  FIGS. 32A and 32B , illustrating how different rotational forces may be used to activate such switches. In  FIG. 33 , a data storage device  950  includes a first rotation activatable mechanical switch  952  and a second rotation activatable mechanical switch  954 . First rotation activatable mechanical switch  952  is oriented with mass  956  at the radial outward end of beam  958 , which runs in a radial direction. Beam  958  may be moved toward contact  960  by inertial force FA during angular acceleration in the direction indicated by the arrow ω, which indicates angular velocity. FA is proportional to the change in the angular velocity ω with respect to time, dω/dt, and has a positive value when the data storage device is accelerating. FA will be zero when the data storage device is rotating at a constant angular velocity, or when it is still. During angular deceleration, beam  958  may be moved toward contact  962 , in the opposite direction of arrow ω, by inertial force FD. FD is proportional to the change in the angular velocity w with respect to time, dω/dt, and has a positive value when the data storage device is decelerating. FD will be zero when the data storage device is rotating at a constant angular velocity, or when it is still. Second rotation activatable mechanical switch  954  is oriented with beam  964  parallel to VT, the tangential velocity, and perpendicular to the radial direction. Switch  954  includes mass  966  at the end of beam  964 . Second rotation activatable mechanical switch  954  may be activated when by centrifugal force FC, which is proportional to the square of the angular velocity, ω 2 . Accordingly, FC, will have a positive value for all non-zero values of angular velocity. By selecting the positioning of a rotation activatable mechanical switch appropriately, the switch may be made responsive to various combinations of forces associated with angular acceleration and centripetal acceleration (centrifugal forces). 
     Data storage devices according to embodiments as described above may include a substrate configured for rotating access, a data storage medium capable of storing machine-readable data carried by the substrate, and a rotation activatable switch configured to undergo a change in state in response to rotation to render unusable at least a portion of machine-readable data stored on the substrate. A change in state may include changing from an open configuration to a closed configuration, or changing from a closed to an open configuration. In some embodiments, the rotation activatable switch may be a centrifugally activatable switch. In other embodiments, the rotation activatable switch may be activatable by angular acceleration of said substrate, or by angular deceleration of said substrate. Various rotation activatable switches designs may be used. The rotation activatable switch may be a micromechanical switch or a fluid switch. In some embodiments, the rotation activatable switch may be a maintained contact switch, while in others it may be a momentary contact switch. The rotation activatable switch may include a cantilever. As depicted in  FIGS. 32A and 32B , a cantilever may include a beam having a mass at its end. 
     In some embodiments, e.g., as depicted in  FIG. 44  the data storage device  1400  may include electronic circuitry  1402 , and the rotation activatable switch  1404  may be configured to control an electrical connection between at least two portions of said electronic circuitry. Either opening or closing of a switch may be used to produce degradation or modification of data, data storage medium, or substrate in region  1406 . When rotation activatable switch  1404  is closed, contact  1408  in cantilever  1410  touches contact  1412 , connecting lines  1414  and  1416 . The data storage device may include a power source  1418 , and the rotation activatable switch may be configured to control delivery of power from the power source to at least a portion of the data storage device. Line  1420  connects power source  1418  to region  1406  in electronic circuit  1402 . Various methods of producing degradation or modification of data, data storage medium, or substrate with electronic circuitry are shown in  FIGS. 28A  and B,  FIGS. 29A  and B and  FIGS. 30  A and B. The data storage device may include a power receiver coil, with the rotation activatable switch configured to control the receipt of power by or distribution of power from the power receiver coil. 
     According to various embodiments, a limited use memory device may include a substrate, machine-readable data stored on the substrate, and at least one centrifugally activatable switching mechanism on the substrate, with the switching mechanism configured to produce modification of a feature of the memory device. The feature may include, but is not limited to, an optical feature, an electrical feature, or a magnetic feature. The feature may be a feature of the substrate, the machine-readable data, the data storage medium in which the machine-readable data is stored, electronic circuitry on the substrate, or any of various other features that influence presence or readability of data. Modification of the feature may render at least a portion of said machine-readable data inaccessible. In some embodiments, modification of the feature may disable reading of at least a portion of the machine-readable data from the data storage device. The portion of machine readable data comprises information necessary for reading additional data from said data storage device. The information may be, for example, decryption key or index information. In some embodiments, modification of the feature may enable reading of at least a portion of the machine-readable data from the data storage device. Modification of the feature may cause destruction or modification of at least a portion of the machine-readable data, or it may include modification of readability of at least a portion of the machine-readable data. In some embodiments, prior to modification of the feature a first portion of data on the disk may be readable, and following modification of the feature a second portion of data on the disk may be readable. 
     The limited use memory device may include a plurality of centrifugally activatable switching mechanisms that are activatable in sequence over a plurality of uses of the memory device and configured such that activation of the plurality of switching mechanisms renders at least a portion of the machine-readable data inaccessible. A use of the memory device may include subjecting the memory device to at least one of angular acceleration or deceleration, for example. A disk  1500  with a plurality of rotation activatable mechanisms  1502 ,  1504 ,  1506 , and  1508  is depicted in  FIG. 45 . Operation of disk  1500  is substantially the same as for the device depicted in  FIG. 25 , with mechanical switching mechanisms in place of fluid switching mechanisms. As described in connection with  FIG. 25 , rotation activatable mechanisms may be configured to be activated at different levels of centrifugal force, e.g., by adjusting the stiffness of the beam portion of each cantilever appropriately. Beam portion  1510  is indicated in rotation activatable mechanism  1502 . 
     In some embodiments, the data storage device may be an optically readable disk. In some embodiments, the centrifugally activatable switching mechanism may be activatable by spinning the substrate in an optical disk drive at normal read speeds, while in other embodiments, the centrifugally activatable switching mechanism may be activatable by spinning the substrate in an optical disk drive at speeds above normal read speeds. In some embodiments, the data storage device may be a magnetically readable disk, and the centrifugally activatable switching mechanism may be activatable by spinning the substrate in a magnetic disk drive at normal read speeds, while in some embodiments, the centrifugally activatable switching mechanism may be activatable by spinning the substrate in a magnetic disk drive at speeds above normal read speeds. 
     According to certain embodiments, the data storage device may include a substrate, a data storage medium on the substrate that is degradable upon exposure to a degradation-inducing influence, and a rotation activatable switching mechanism for controlling exposure of the data storage medium to the degradation-inducing influence. Activation of the rotation activatable switching mechanism may produce direct exposure of the data storage medium to the degradation-inducing influence, or it may facilitate degradation of the data storage medium by a secondary degradation-inducing influence. Secondary degradation inducing influences may include, for example, light, electromagnetic fields, and heat. The rotation activatable switching mechanism may be a microswitch that is closable upon exposure to sufficient centrifugal force, such that closure of the microswitch permits electrical current to flow into a selected portion of the data storage device. A microswitch may include a microfabricated cantilever, for example, as depicted in  FIGS. 32A and 32B . 
     As shown in  FIGS. 46A and 46B , a data storage device  1550  may include a substrate  1552 , a degradation sensitive data storage medium  1554  on substrate  1552 , with the data storage medium being degradable upon exposure to a degradation-inducing influence, and a rotation-responsive barrier portion  1556  configured to shield data storage medium  1554  from the degradation-inducing influence. The degradation inducing influence may be, for example, light. The rotation-responsive barrier portion  1556  may include a removable barrier portion that, upon subjection to sufficient centrifugal force, is removable to permit exposure of the data storage medium to the degradation-inducing influence. The barrier portion may be removed as at least one structural unit, as depicted in  FIGS. 46A and 46B . Alternatively, the barrier portion may be removed by evaporation, as depicted in  FIGS. 47A and 47B . Data storage device  1570  includes substrate  1572 , degradation sensitive data storage medium  1574 , and evaporation sensitive barrier  1576 . Following rotation of data storage device  1570 , evaporation sensitive barrier  1576  may becomes sufficiently permeable or porous that a degradation inducing influence may produce degradation of degradation sensitive data storage medium  1574 . Suitable materials for evaporation sensitive barrier  1576  may include moisture permeable coatings, such as those having relatively high water vapor transmission rates (WVTRs) that allow moisture or other materials to pass. In one approach, moisture passing through the evaporation sensitive barrier can degrade an underlying material. In another approach, moisture exiting through the evaporation sensitive barrier  1576  permits drying of a material beneath the evaporation sensitive barrier  1576  and the dried material can block or diffuse light or otherwise degrade data. In another embodiment, as depicted in  FIGS. 48A and 48B , a data storage device  1590  may include a rotation-responsive barrier portion that may be a modifiable barrier portion  1592  that, upon being subjected to sufficient centrifugal force is converted to a modified state  1592 ′ to permit exposure of the data storage medium  1594  to the degradation-inducing influence. This may occur in a number of ways. For example, exposure of the barrier portion  1592  to sufficient centrifugal force may modify an optical transmissivity, an electrical conductivity, or a permittivity of the barrier portion. Suitable rotation sensitive materials for modifiable barrier  1592  may include a liquid crystal or a MEMS structure, such as the moving droplet structure described in  Electrostatic Actuation of Microscale Liquid - Metal Droplets  Laurent Latorre, Joonwon Kim, Junghoon Lee, Associate Member, IEEE, Peter-Patrick de Guzman, Hyesog J. Lee, Pascal Nouet JOURNAL OF MICROELECTROMECHANICAL SYSTEMS, VOL. 11, NO. 4, AUGUST 2002, for example. 
     According to various embodiments as disclosed herein, use of a disk may be controlled by a method that includes reading data from the disk and rotating the disk to activate a rotation activatable mechanical switch on the disk. Rotating the disk to activate the rotation activatable mechanical switch may be performed prior to reading data from said disk, as illustrated in  FIG. 36 , subsequent to reading data from said disk, as illustrated in  FIG. 35  or simultaneous with reading data from said disk, as illustrated in  FIG. 37 . The method may also include checking for previous activation of the rotation activatable mechanical switch prior to reading data from said disk. In particular, reading data from the disk may be performed if no previous activation of the rotation activatable mechanical switch is detected, as exemplified by the method of  FIG. 39 . Alternatively, reading data from the disk may be performed if no more than a selected number of previous activations of the rotation activatable mechanical switch are detected, as shown in  FIG. 40 . According to various methods disclosed herein, activation of the rotation activatable mechanical switch causes degradation of a data storage medium on the disk or modification of data stored on the disk. Activation of the rotation activatable mechanical switch may prevent reading of at least a portion of data from the disk. In some embodiments, activation of the rotation activatable mechanical switch may initiate a process wherein at least a portion of the data stored on the disk is rendered unusable, modified, or destroyed. 
     A disk drive system suitable for use with various embodiments of data storage devices as disclosed herein may include a receptacle for receiving a substrate configured for rotating access having stored data and a rotation activatable switching mechanism thereon, a read head for reading data from the substrate, a motor capable of spinning the substrate in a controlled pattern in response to a control signal, and a drive controller including one or more of control hardware, software, or firmware configured to generate a control signal for causing the motor to spin said substrate in a controlled pattern sufficient to produce activation of the rotation activatable switching mechanism. An exemplary embodiment is depicted in  FIG. 2 . The drive may include a detector capable of sensing an outcome of activation of the rotation activatable switching mechanism. In some embodiments of the disk drive system, the read head may be configured to function as the detector. The read head may be, for example, and optical read head or a magnetic read head. The motor may be capable of spinning the substrate at a speed higher than the normal read speed for the drive in order to produce activation of the rotation activatable switching mechanism. 
     Drive control software for controlling a disk drive for use with a disk having a rotation sensitive mechanism may include read head position instructions, including commands for controlling the position of a read head with respect to a disk received in a disk drive, disk read position instructions including commands for controlling rotational movement of a disk received in the disk drive during reading, read instructions for managing reading of data from the disk with a sensor; and data degradation instructions for controlling duration and intensity of rotation of the disk at levels sufficient to induce degradation in the disk. In some embodiments, data degradation instructions may control disk rotation to induce degradation of a data storage medium on the disk. In some embodiments, data degradation instructions may control disk rotation to induce degradation of a disk substrate. 
     A drive as described herein may be incorporated into a computer system, as shown in  FIGS. 1 and 34 , which may include various components such as a processor, a system bus, an input device, an output device, a drive capable of reading data from a substrate configured for rotating access, and data storage media containing software instructions capable of controlling said drive to produce rotation of the substrate of intensity and duration capable of activating a rotation activatable mechanism to render at least a portion of machine readable data stored on the substrate inaccessible. 
     Certain data storage devices as described herein may be manufactured according to a method as shown in  FIG. 49 , which includes forming a substrate configured for rotating access at step  1602 , providing a data storage medium on said substrate at step  1604 , and forming an electrical circuit on the substrate at step  1606 . The electrical circuit may include a rotation-activatable mechanical switch and be configured to produce degradation of a least a portion of data stored in the data storage medium upon activation of the rotation-activatable mechanical switch. The manufacturing method may also include a step of storing machine readable data in the data storage medium. By combining appropriately oriented rotation activatable fluid release and/or switching mechanisms, which may include fluid and/or mechanical switches, with suitable fluid or electrical circuitry, it is possible to produce a modification (e.g., activation or deactivation) of a data storage device in following a selected number of uses of the device. Data storage devices configured in this manner may be used in various systems that utilize data storage devices.  FIG. 34  illustrates a system  1000  configured to make use of a data storage device  1010 . The system may be a computer system, a CD or DVD player, or various other systems which may make use of data storage device configured for rotating access. System  1000  includes CPU (central processing unit)  1002 , system memory  1004 , one or more I/O (input/output) devices  1006 , and data storage device drive  1008 . Data storage device drive  1008  may be adapted to receive a data storage device  1010 . Data, power, and control signals may be transmitted between the various system components via bus  1012 . System memory  1004  may include ROM  1014  and RAM  1016 . Data storage device drive  1008  may be controlled by device driver software  1018  resident in RAM  1016 . Drive interface  1020 , which may include hardware, software, or firmware, may assist the transfer of signals between data storage device drive  1008  and the rest of system  1000 . The operation of data storage device drive  1008  may be modified or controlled at the level of device driver software  1018 , or drive interface  1020 , as well as by modifications to data storage device drive  1008 . In some embodiments, data storage device  1010  may be configured so that it will be modified or inactivated following a selected number of uses. In some embodiments, components of system  1000  other than data storage device  1010  may operate in a conventional manner. In other embodiments, selected components of system  1000  may include features that are specialized for use with a data storage device  1010  having rotation activatable features. System  1000  may be modified at the level of drive  1008 , drive interface  1020 , or program code  1018  residing in RAM  1016 . Drive  1008  or drive interface  1020  may be modified at the hardware, firmware, or software level. Program code  1018  may be system software or application program software. As discussed previously in connection with  FIG. 25 , system  1000  may be modified to control the speed of rotation of data storage device  1010  within drive  1008  to activate fluid release devices (or other rotation activatable mechanisms) in sequence based upon different thresholds for activation. System  1000  may be configured to detect prior activation of a rotation activatable mechanism on data storage device  1010 . Modifications to data storage device  1010  associated with prior activation may be detected by various means. If the modification includes modification of data or modification of accessibility of a particular portion of data, the modification may be detected when an attempt is made to read data from data storage device  1010 , e.g. by failure of reading. In some embodiments, a rotation activatable mechanism may produce modification of a mechanical, optical, electrical, magnetic, chemical, or other property of the data storage device. Such modifications may be manifested as modifications of data or accessibility of data, but are not limited to modification of data or data accessibility. In some embodiments, modifications may be detectable by optical, electrical, magnetic, or other means, and the presence of the modification may serve as an instruction to the system to discontinue reading of the disk, or to operate in a specified manner (e.g., by increasing the speed of rotation of the disk, delivering light to a selected region of the disk, etc.). 
     The following flow diagrams are illustrative of various approaches that may be taken for controlling operation of a system as depicted in  FIG. 33 . Some approaches make use of conventional drive operation, while others may make use of modifications to conventional drive operation. 
       FIG. 35  is a flow diagram of a method of activating a rotation activatable control mechanism. According to various embodiments, described previously, various rotation activatable mechanisms may be used to control access to data on a data storage device, by modifying or degrading data, or by modifying access to the data by modifying all or a portion of the data storage device. Rotation activatable mechanisms may be rotation activatable control mechanisms. At step  1052 , data is read from a disk (or other data storage device configured for rotating access). At step  1054 , the disk is rotated to activate a rotation activatable control mechanism. A rotation activatable control mechanism may include, for example, a rotation activatable switch or fluid release device, as described previously. Because the rotation activatable control mechanism is activated after data is read from the device in this example, the use of a rotation activated control mechanism that produces immediate (or substantially immediate) destruction of data, or otherwise rapidly renders data unusable or inaccessible may be used. Rotation activated control mechanisms that initiate a gradual process by which data is destroyed or rendered inaccessible may also be used. 
       FIG. 36  is a flow diagram of a further exemplary method of activating a rotation activatable control mechanism. At step  1102 , a disk is rotated to activate a rotation activatable control mechanism. Subsequently, at step  1104 , data is read from the disk. In this example, the rotation activatable control mechanism may initiate a process that causes data to be destroyed or rendered unusable or inaccessible over time. Immediate destruction of data may be incompatible with the subsequent step of reading data from the disk. 
       FIG. 37  is a flow diagram of a further exemplary method including activation of a rotation activatable control mechanism. At step  1152 , a data storage device configured for rotating access is rotated to activate a rotation activatable control mechanism substantially simultaneously with reading of data from the data storage device. 
       FIG. 38  is a flow diagram providing further detail of method such as that depicted in  FIG. 34 . At step  1202  of  FIG. 38 , data is read from a disk. Reading data from the disk may including rotating the disk to select a location on the disk from which data is to be read. At step  1204 , the disk is rotated to open a rotation activatable barrier. Opening a rotation activatable barrier may include rotating a disk at substantially the same velocity as used during reading data from the disk, or it may include rotating the disk at a different velocity, in a different direction, or in some other pattern differing from the rotation pattern used during reading of data from the disk. Fluid may be released by opening of the rotation activatable barrier, to produce modification of all or a portion of the data storage device by any of various methods as described herein. 
       FIG. 39  is a flow diagram of a method in which a rotation activatable control mechanism is used to control access to data on a disk. A process of reading data from a disk is initiated at step  1250 . At decision point  1252 , a check is performed to determine whether a rotation activatable control mechanism has been activated previously. Determination of previous activation of a rotation activatable control mechanism may be by various methods, as described previously, either through detecting the inability to read data from the disk, the reading of ‘bad’ data from the disk, or the detecting of a modified feature of the disk. If previous activation of a rotation activatable control mechanism is not detected, process control moves to step  1254 , and data is read from the disk. After data is read from the disk, the disk is rotated to activate a rotation activatable control mechanism at step  1256 . If subsequent attempts are made to read data from the disk, process control will begin again at step  1250 . When it is determined at step  1252  that the rotation activatable control mechanism has been activated previously, the result will be affirmative, and the process will end (step  1258 ), and no data will be read from the disk. 
       FIG. 40  is a flow diagram of a further embodiment of a method of controlling access to data on a disk. In this exemplary embodiment, access to data on the disk is denied after a total of N accesses to the data. After initiation of the method at step  1300 , n, the number of times that a rotation activatable control mechanism on the disk has been activated, is determined at step  1302 . If the disk has never been activated previously, zero activations will be detected. Activation of a rotation activatable control mechanism may produce various types of detectable changes on a data storage device, including but not limited to optically detectable changes, magnetically detectable changes, electrically detectable changes, among others. At decision point  1304 , if n&lt;N, process control moves to step  1306 , where data is read from the disk. At step  1308 , the disk is rotated to activate a rotation activatable control mechanism, increasing the number of detectable changes on the disk by one. This is equivalent to increasing the value of n to n+1. Reading of data accomplished, the process ends at step  1310 . If it is desired to read data from the disk again, the process may be repeated again, starting at step  1300 . When data has been read from the disk N times, on the (N+1)th attempt to read data from the disk, at step  1302 , a value of n=N will be obtained. At step  1304 , the response to the query n&lt;N, will be ‘No’ and process control will jump to endpoint  1310 . Thus, no further reads of data from the disk will be permitted. The method presented in  FIG. 39  may be used, for example, in connection with a disk as shown in  FIG. 25 . Degradation of degradation sensitive regions  764 ,  772 ,  780 ,  788  may be detected as an indicator of previous activation of the disk; when all four regions have been degraded, indicating that four reads of the disk have been performed, then no further reading of data may be permitted. Further reading may be prevented in by configuring the software controlling reading of the disk so that it will not attempt a read when all degradation sensitive regions have been degraded (even if the data on the disk is present and readable). Alternatively, if the degradation sensitive regions contain information necessary for reading data from other portions of the disk (possibly redundant copies of the same information, or possibly different information in different degradation sensitive regions) when all four degradation sensitive regions have been degraded, the information necessary for reading data from the disk is no longer available on the disk. 
       FIG. 41  is a flow diagram of a method of manufacturing a data storage device according to various embodiments as disclosed herein. The method includes the steps of: forming a substrate configured for rotating access at step  1322 , providing a data storage medium on said substrate at step  1324 , and forming a rotation-activatable fluid release mechanism on said substrate at step  1326 . The rotation-activatable fluid release mechanism may be configured to release fluid within said data storage device to produce degradation of at least a portion of data stored in said data storage device. In related embodiments, the method may also include the steps of storing machine readable data in the data storage medium, and loading the fluid release mechanism with a fluid. 
       FIG. 42  is a flow diagram of a method of operating a disk drive, which includes the steps of adjusting the radial position of a read head with respect to a disk received in the disk drive, as shown at step  1332 ; controlling the rotation of a disk received in the disk drive to permit reading of data from the disk, as shown at step  1334 ; reading data from the disk with a sensor (step  1336 ); and, at step  1338 , controlling rotation of the disk to produce activation of a rotation sensitive structure configured to produce degradation of data on the disk. 
     In some embodiments, as described above, the disk drive may be configured for use with rotation-sensitive disks.  FIG. 43  is a flow diagram of a method of configuring a disk drive for use with a rotation-sensitive disk. The method includes a first step  1352  of providing read head position instructions, including commands for controlling the position of a read head with respect to a disk received in the disk drive. Next, at step  1354 , motor control instructions including commands for controlling rotational movement of a disk received in the disk drive during reading are provided. At step  1356 , read instructions for managing reading of data from the disk with a sensor are provided. Finally, at step  1358 , data degradation instructions are provided for controlling duration and speed of rotation of the disk at levels sufficient to induce degradation in the rotation-sensitive disk. One or more of the read head position instructions, motor control instructions, read instructions and data degradation instructions may be provided in the form of software, hardware or firmware. For example, instructions may be provided on a disk that is provided to a purchaser of the disk drive, stored in static or dynamic memory, or configured in an ASIC (application specific integrated circuit) or other electronic circuitry. Memory or data storage devices containing the instructions, or electronic circuitry embodying such instructions may be a part of the disk drive or part of a computer or other device in which the disk drive may be installed. 
     With regard to the hardware and/or software used in the control of drives for data storage device according to the present embodiments, and particularly to the control of data reading and disk rotation, those having skill in the art will recognize that the state of the art has progressed to the point where there is little distinction left between hardware and software implementations of aspects of such systems; the use of hardware or software is generally (but not always, in that in certain contexts the choice between hardware and software can become significant) a design choice representing cost vs. efficiency or implementation convenience tradeoffs. Those having skill in the art will appreciate that there are various vehicles by which processes and/or systems described herein can be effected (e.g., hardware, software, and/or firmware), and that the preferred vehicle will vary with the context in which the processes are deployed. For example, if an implementer determines that speed and accuracy are paramount, the implementer may opt for a hardware and/or firmware vehicle; alternatively, if flexibility is paramount, the implementer may opt for a solely software implementation; or, yet again alternatively, the implementer may opt for some combination of hardware, software, and/or firmware. Hence, there are several possible vehicles by which the processes described herein may be effected, none of which is inherently superior to the other in that any vehicle to be utilized is a choice dependent upon the context in which the vehicle will be deployed and the specific concerns (e.g., speed, flexibility, or predictability) of the implementer, any of which may vary. 
     In some embodiments, portions of the subject matter described herein may be implemented via Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), digital signal processors (DSPs), or other integrated formats. However, those skilled in the art will recognize that some aspects of the embodiments disclosed herein, in whole or in part, can be equivalently implemented in standard integrated circuits, as one or more computer programs running on one or more computers (e.g., as one or more programs running on one or more computer systems), as one or more programs running on one or more processors (e.g., as one or more programs running on one or more microprocessors), as firmware, or as virtually any combination thereof, and that designing the circuitry and/or writing the code for the software and/or firmware would be well within the capabilities of one of skill in the art in light of this disclosure. In addition, those skilled in the art will appreciate that certain mechanisms of the subject matter described herein are capable of being distributed as a program product in a variety of forms, and that an illustrative embodiment of the subject matter described herein applies equally regardless of the particular type of signal bearing media used to actually carry out the distribution. Examples of a signal bearing media include, but are not limited to, the following: recordable type media such as floppy disks, hard disk drives, CD ROMs, digital tape, and computer memory; and transmission type media such as digital and analog communication links using TDM or IP based communication links (e.g., links carrying packetized data). 
     In a general sense, those skilled in the art will recognize that the various aspects described herein which can be implemented, individually and/or collectively, by a wide range of hardware, software, firmware, or any combination thereof can be viewed as being composed of various types of “electrical circuitry.” Consequently, as used herein “electrical circuitry” includes, but is not limited to, electrical circuitry having at least one discrete electrical circuit, electrical circuitry having at least one integrated circuit, electrical circuitry having at least one application specific integrated circuit, electrical circuitry forming a general purpose computing device configured by a computer program (e.g., a general purpose computer configured by a computer program which at least partially carries out processes and/or devices described herein, or a microprocessor configured by a computer program which at least partially carries out processes and/or devices described herein), electrical circuitry forming a memory device (e.g., forms of random access memory or an optical or ferromagnetic memory structure), and/or electrical circuitry forming a communications device (e.g., a modem, communications switch, or optical-electrical equipment). 
     The foregoing detailed description has set forth various embodiments of the devices and/or processes via the use of block diagrams, flowcharts, and/or examples. Insofar as such block diagrams, flowcharts, and/or examples contain one or more functions and/or operations, it will be implicitly understood by those with skill in the art that each function and/or operation within such block diagrams, flowcharts, or examples can be implemented, individually and/or collectively, by a wide range of hardware, software, firmware, or virtually any combination thereof. 
     Those skilled in the art will recognize that it is common within the art to describe devices for data storage and reading in the fashion set forth herein, and thereafter use standard engineering practices to integrate such described devices and/or processes into systems including data storage devices as exemplified herein. That is, at least a portion of the devices and/or processes described herein can be integrated into a system including a data storage device via a reasonable amount of experimentation. Those having skill in the art will recognize that such systems generally include one or more of a memory such as volatile and non-volatile memory, processors such as microprocessors and digital signal processors, computational-supporting or associated entities such as operating systems, user interfaces, drivers, sensors, actuators, applications programs, one or more interaction devices, such as data ports, control systems including feedback loops and control implementing actuators (e.g., devices for sensing position and/or velocity and/or acceleration or time-rate-of-change thereof; control motors for moving and/or adjusting components and/or quantities). A typical system may be implemented utilizing any suitable available components, such as those typically found in appropriate computing/communication systems and/or data storage and reading systems, combined with standard engineering practices. 
     The foregoing-described aspects depict different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermediate components. Likewise, any two components so associated can also be viewed as being “operably connected”, or “operably coupled”, to each other to achieve the desired functionality. 
     While particular aspects of the present subject matter described herein have been shown and described, it will be obvious to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from this subject matter described herein and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of this subject matter described herein. Furthermore, it is to be understood that the invention is defined by the appended claims. It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should NOT be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” and/or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense of one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense of one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together). 
     Although the methods, devices, systems and approaches herein have been described with reference to certain preferred embodiments, other embodiments are possible. As illustrated by the foregoing examples, various choices of system configuration may be within the scope of the invention. As has been discussed, the choice of system configuration may depend on the intended application of the system, the environment in which the system is used, cost, personal preference or other factors. Data storage device design, manufacture, and control processes may be modified to take into account choices of system components and configuration, and such modifications, as known to those of skill in the arts of data storage and retrieval structures and systems, fluid control structures, and electronics design and construction, may fall within the scope of the invention. Therefore, the full spirit or scope of the invention is defined by the appended claims and is not to be limited to the specific embodiments described herein.