the following description is of the best - contemplated mode of carrying out the invention . this description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense . the scope of the invention is best determined by reference to the appended claims . according to the invention , a method of manufacturing bearing at first is to form a desired shape of a bearing having a through hole by cutting or turning or by powder sintering way . the bearing , as shown in fig1 , is preferably made of copper . an inner wall 10 defining the through hole is coated with a photoresist 20 uniformly , as shown in fig2 , by spray coating , dipping , spin coating or centrifugal coating . the photoresist 20 coated on the inner wall 10 comprises polyimide , diazonium salt , or sulfonamide chlorine . in this embodiment of the invention , the photoresist 20 coated on the inner wall 10 is a kind of positive photoresist , for example “ electrolube prp - 200 .” then , the photoresist 20 coated on the inner wall 10 is dried by baking process for securing the adhesion between the inner wall 10 and the photoresist 20 . as shown in fig3 , an ultraviolet lamp 30 with a mask 40 attached on the surface thereof is provided . the mask 40 comprises patterns of pressure - generating grooves 401 and an oil reservoir 402 thereon . the ultraviolet lamp 30 is preferably a cold cathode fluorescent lamp or an optical fiber illuminant , which can emit ultraviolet light having wavelength ranging from 350 nm to 450 nm . with positive photoresist in this embodiment , the patterns of pressure - generating grooves 401 and oil reservoir 402 are transparent on the mask and the other portion thereof is opaque . in this embodiment , the groove on the mask is v - shaped . as shown in fig4 , after baking process , the ultraviolet lamp 30 with the mask 40 attached thereon is inserted into the through hole of the bearing , and activated to emit ultraviolet light to execute an exposure process . during the exposure process , a part of the photoresist 20 is sensitized by the ultraviolet light emitted from the ultraviolet lamp 30 through the patterns on the mask 40 . after the exposure process , as shown in fig5 , the ultraviolet lamp 30 is removed , and the exposed photoresist is removed by a developer to make the underneath portions of the inner wall 10 appear . the concentration of the developer is determined by the type of photoresist . in this embodiment , naoh solution is used to serve as a developer . after the developing process , the bearing is cleaned by water . the appeared inner wall 10 , the portion of the inner wall 10 uncovering the photoresist 20 , is then etched by an etchant to form grooves 12 and an oil reservoir 13 with desirable dimensions . the etchant can comprise ferric chloride , cupric chloride or ammonium sulfide solution . after the etching process , the bearing is cleaned by water , and the photoresist 20 remaining on the inner wall 10 is stripped by a stripping solution such as alcohol . then , the bearing is cleaned by water to remove the solutions and expose the grooves 12 and the oil reservoir 13 . the finished bearing of the invention is shown in fig6 . the feature of the invention is to form the pressure - generating grooves on the inner wall of a bearing by photolithography , so the solutions used in this invention are not limited . in addition , the grooves on the inner wall are also not limited in any shape , and it can be in fish bone shape , substantially - modified - x - shape , twill or straight stripe shape . according to a second embodiment of the invention , a method for manufacturing the bearing at first is to form a desired shape of a bearing having a through hole and then coat a photoresist on an inner wall of the through hole in the bearing by the similar steps to the first embodiment , as shown in fig1 and 2 . preferably , the bearing 1 is made of copper or alloys thereof . the photoresist 20 is preferably a positive photoresist such as , but not limited to , photosensitive polyimide ( pspi ) photoresist , diazo photoresist , chlorine sulfonamide , naphthoquinone diazide derivative or novolakresin derivative , and can be coated by spray coating , dipping , spin coating or centrifugal coating . in the second embodiment , the photoresist 20 is azp - 4620 comprising of naphthoquinone diazide derivative and novolakresin derivative produced by clariant incorporation . the photoresist 20 coated on the inner wall 10 can be cured by baking . alternatively , the photoresist 20 can be cured by natural drying at room temperature . furthermore , as shown in fig7 , a lamp 30 a , also referred to as a ultraviolet lamp , capable of passing through the through hole and emitting light in ultraviolet spectrum , wherein the lamp 30 a having a mask 40 a with a pressure - generating groove pattern 401 a thereon , is provided . specifically , the mask 40 a can be a slice having the pressure - generating groove pattern 401 a thereon , attached to the lamp 30 a , or have metal pattern with the pressure - generating groove pattern 401 a thereon , for example chromium ( cr ), formed on the lamp 30 a . the lamp 30 a is capable of emitting a light for photosensitizing the photoresist 20 . in this embodiment , the light is preferably ultraviolet having a wavelength of between about 350 nm and 450 nm . in this embodiment , a portion of the mask 40 a , where the pressure - generating groove pattern 401 a located , is opaque . the pressure - generating groove pattern 401 a , as shown in fig7 , is only an exemplary embodiment , its shape can be varied with design and is thus not limited thereto . as shown in fig8 , the lamp 30 a is placed inside the through hole of the bearing body 1 after curing and baking , the power thereof is then turned on to emit ultraviolet light so that the photoresist 20 can be exposed . thus , a portion of the photoresist 20 corresponding to a transparent portion of the mask 40 a is photosensitized . after exposing , the lamp 30 a is then removed . the photosensitized portion of the positive photoresist 20 is removed by a developer to appear a portion of the inner wall 10 , as shown in fig9 . in this embodiment , the developer can be , for example az - 300 made of tetramethyl ammonium hydroxide , produced by clariant incorporation . note that the composition and concentration of the developer depends on the material of the photoresist , thus is not limited to the described example . referring to fig1 a , the appeared portion of the inner wall 10 , without covered with the photoresist 20 , is coated with a wear - resistant material , for example nickel - cobalt ( nico ) alloy , nickel - phosphor ( nip ) alloy or nickel - cobalt - phosphor ( nicop ) alloy , by electroplating to form a deposited layer 50 . fig1 b is a fragmentary sectional view of the bearing in fig1 a . in fig1 a , the photoresist 20 remaining on the inner wall 10 is stripped by a stripping solution to form a desirable , pressure - generating groove 12 a between the two adjacent deposited layer 50 . in this embodiment , the stripping agent can be acetone . thereafter , the solutions , using foregoing steps , are cleaned with water to perform a dynamic bearing according to the embodiment of the invention . fig1 b is a fragmentary sectional view of the bearing in fig1 a . in this embodiment , the deposited layer formed by electroplating is not limited by the depth and width of the pressure - generating groove . furthermore , the formation of the deposited layer can be modified by adjusting electroplating parameters , for example the electroplating duration , rate of electroplating , electroplating plus current and electroplating liquor additive . as a fragmentary sectional view of the bearing 1 shown in fig1 , a thickness of the deposited layer 50 is greater than that of the photoresist 20 . an arched top is formed , decreasing the area of a surface contacting a shaft for reducing friction between the deposited layer and the shaft . additionally , by supplying different current to the exposed surface of the inner wall 10 , the thickness of the deposited layer 50 can be changed as desired , as a fragmentary sectional view of another bearing 1 shown in fig1 . according to a third embodiment of the invention , a method for manufacturing the bearing is substantially similar to the second embodiment . the formation of the deposited layer , according to the third embodiment of the invention , differs only slightly from the second embodiment . the similar steps , for example modeling , exposing and developing , already described in the second embodiment are not described again here . note that the bearing 1 in the third embodiment can be metal such as brass , or nonmetal such as aluminum oxide ceramic . fig1 a and 14b , a diagrammatic view and a fragmentary sectional view of the bearing 1 after developing , respectively . in this embodiment , subsequent to the developing step , a wear resistant material , for example nickel - cobalt ( ni — co ) alloy , silicon carbon ( sic ), tungsten carbide ( wc ), is deposited on the photoresist 20 and the surface of the inner wall 10 , which is not covered by the photoresist 20 ( also referred to as the surface of the appeared portion of the inner wall 10 ), by sputtering to form the deposited layer 60 . in fig1 a and 15b , the photoresist 20 and the wear resistant material deposited thereon are stripped by lift - off , to form the pressure - generating groove 12 between the two adjacent deposited layers 60 , so as to perform a dynamic bearing according to the third embodiment of the invention . the process of forming the deposited layer of the fourth embodiment of the invention differs only slightly from the second embodiment . the similar steps to the second embodiment , for example modeling , exposing and developing , may refer to fig7 - 9 and its corresponding descriptions , and are not provided again here . note that the bearing in this embodiment can be metal such as aluminum or alloys thereof . subsequent to the developing step , a chemical reaction occurs between the surface of the inner wall 10 , which is not covered by the photoresist 20 , with ambient reactant to form a compound . in this embodiment , the bearing 10 comprising , for example , aluminum or aluminum alloy , is dipped into oxalic acid solvent . in fig1 a and 16b , an anode oxidation treatment is executed , the wear resistant material is then generated on the surface of the inner wall 10 , which is not covered by photoresist 20 , to form the deposited layer 70 comprising aluminum oxide . the photoresist 20 , reminding on the surface of the inner wall 10 , is removed by a stripping agent , such as acetone , following by washing with water and drying , to form the pressure - generating groove between the two adjacent deposited layers 70 . the dynamic bearing , as shown in fig1 a and 17b , according to the fourth embodiment of the invention , is complete . noted that , in this embodiment the ambient reactant is liquid phase , but the ambient reactant can be liquid or gas phase , have a capable of reaction with the surface of the inner wall of the bearing . fig1 is a diagrammatic view illustrating steps for manufacturing the bearing according to a fifth embodiment of the invention , in which the baring is shown in cross sectional view . in this embodiment , the bearing is preferably made of copper or alloys thereof . as shown in ( a ) of fig1 , the surface of inner wall of the bearing 1 is coated by photoresist 20 a by the same steps as the first embodiment . thus , the repeated descriptions are not provided . in this embodiment , the photoresist 20 a is a negative photoresist , for example , comprising acrylic resin and propylene glycol monomethyl ether acetate , or a negative photoresist comprising epoxy resin and gamma butyrolactone . as shown in ( b ) of fig1 , the lamp 30 a capable of emitting a wavelength in ultraviolet is placed inside the bearing 1 to expose the photoresist 20 a . in this embodiment , the lamp 30 a has a mask with a pressure - generating groove pattern thereon and has an opaque area where the groove pattern located . in this embodiment , the lamp 30 a can be similar to the one shown in fig7 . after exposing , the lamp 30 a is removed . a portion of the photoresist 20 a without photosensitizing is cleaned by developer and the portion of the inner wall made of copper is appeared , as shown in ( c ) of fig1 . subsequently , as shown in ( d ) of fig1 , the portion of the inner wall without covering the photoresist 20 a , also referred to as an appeared portion of the inner wall , is etched by an etchant to form a desirable groove 12 . next , the photoresist 20 a reminding on the inner wall is stripped by a stripping agent to form a desirable groove pattern 12 . the steps for manufacturing the bearing are substantially the same as the first embodiment , unless the negative photoresist is utilized in this embodiment . thus , groove pattern of the mask on the lamp in this embodiment is corresponding complement to that in the first embodiment . fig1 is a diagrammatic view illustrating steps for manufacturing the bearing according to a sixth embodiment of the invention , in which the bearing is shown in cross sectional view . in this embodiment , the bearing is preferably made of copper or alloys thereof . as shown in ( a ) of fig1 , the surface of inner wall of the bearing 1 is coated by photoresist 20 a by the similar steps to the first embodiment . thus , the repeated descriptions are not provided . in this embodiment , the photoresist 20 a is a negative photoresist . as shown in ( b ) of fig1 , the lamp 30 capable of emitting a ultraviolet wavelength is placed inside the bearing 1 to expose the photoresist 20 a . in this embodiment , the lamp 30 has a mask with a pressure - generating groove pattern thereon . the groove pattern located on the lamp 30 is transparent . in this embodiment , the lamp 30 can be the same as the one shown in fig3 . after exposing , the lamp 30 is removed . a portion of the photoresist 20 a without photosensitizing is cleaned by a developer and the portion of the inner wall made of copper is appeared , as shown in ( c ) of fig1 . as shown in ( d ) of fig1 , a deposited layer 80 is deposited on the portion of the inner wall , which is not covered with the photoresist 20 a , also referred to as an appeared portion of the inner wall . next , the photoresist 20 a is stripped by a stripping agent and a desirable groove pattern 12 a is formed between the two adjacent deposited layers 80 . this embodiment is the same as the fifth embodiment , unless the groove pattern of the mask on the lamp is transparent . the desirable groove pattern is formed by deposited layers . in the sixth embodiment , the deposited layer 80 is preferably made of a wear resistant material and is formed by the similar step to the second , third and fourth embodiments . fig2 is diagrammatic view illustrating steps for manufacturing a shaft according to a seventh embodiment of the invention , in which the shaft is shown in cross sectional view . in this embodiment , the shaft is formed by cutting , turning or powder sintering and is made of copper or alloys thereof . as shown in ( a ) of fig2 , photoresist 20 is coated on the surface of the shaft 2 by spray coating , dipping , spin coating or centrifugal coating . preferably , the photoresist 20 is made of a positive photoresist . as shown in ( b ) of fig2 , the shaft 2 is placed into a circular lamp 90 capable of emitting ultraviolet wavelength to expose the photoresist 20 . a slice with a pressure - generating groove pattern is attached to an inner surface of the circular lamp 90 . then , the exposing is executed to photosensitize the positive photoresist corresponding to the transparent portion of the slice . in this embodiment , the slice is made of a mask 40 with the pressure - generating groove pattern and an area thereof with the pressure - generating groove pattern 401 located is transparent . after exposing , the shaft is removed from the circular lamp 90 . a portion of the photoresist 20 without photosensitizing is cleaned by a developer and the surface of the shaft made of copper is partly appeared , as shown in ( c ) of fig2 . as shown in ( d ) of fig2 , the surface of the shaft without covering the photoresist 20 , also referred to as an appeared surface of the shaft , is etched by an etchant . the photoresist 20 is then stripped by a stripping agent to form a desirable groove pattern 12 . this embodiment is substantially the same as the first embodiment , unless the groove is formed on the surface of the shaft by photolithography and the circular lamp is utilized to expose the surface of the shaft . fig2 is diagrammatic view illustrating steps for manufacturing a shaft according to an eighth embodiment of the invention , in which the shaft is shown in cross sectional view . in this embodiment , the shaft is formed by cutting , turning or powder sintering , and is made of copper or alloys thereof . as shown in ( a ) of fig2 , the surface of the shaft 2 is coated by photoresist 20 by the similar steps to the seventh embodiment . thus , the repeated descriptions are not provided here . in this embodiment , the photoresist 20 is a positive photoresist . as shown in ( b ) of fig2 , the shaft 2 is placed into a circular lamp ( not shown ) capable of emitting ultraviolet wavelength to expose the photoresist 20 . the exposing step in this embodiment is the same as that in the seventh embodiment unless the mask 40 a with pressure - generating groove located is opaque . after exposing , the shaft is removed from the circular lamp . a portion of the photoresist 20 not photosensitized is cleaned by a developer to appear the surface of the shaft made of copper and form a groove pattern 401 a corresponding to the groove pattern of the mask 40 a , as shown in ( c ) of fig2 . as shown in ( d ) of fig2 , the deposited layer 80 is formed on the surface of the shaft without covering the photoresist 20 , also referred to as an appeared surface of the shaft . the photoresist 20 is then stripped by a stripping agent to form a desirable groove pattern 12 a between the two adjacent deposited layers . this embodiment is substantially the same as the seventh embodiment unless the groove pattern of the mask on the lamp is opaque . thus , the desirable groove pattern is formed by the deposited layer . in this embodiment , the deposited layer 80 is preferably made of wear resistant material and formed by the similar steps to the second , the third and the fourth embodiments . fig2 is diagrammatic view illustrating steps for manufacturing a shaft according to a ninth embodiment of the invention , in which the shaft is shown in cross sectional view and is preferably made of cooper or alloys thereof . as shown in ( a ) of fig2 , the surface of the shaft 2 is coated by photoresist 20 a by spray coating , dipping , spin coating or centrifugal coating . preferably , the photoresist 20 a is a negative photoresist . as shown in ( b ) of fig2 , the shaft 2 is placed into a circular lamp ( not shown ) capable of emitting ultraviolet wavelength to expose the photoresist 20 a . the exposing step in this embodiment is the same as that in the eighth embodiment and the repeated descriptions are not provided here . after exposing , the shaft is removed from the circular lamp . a portion of the photoresist 20 a not photosensitized is cleaned by a developer to appear the surface of the shaft made of copper and form a groove pattern 401 a corresponding to the groove pattern of the mask 40 a , as shown in ( c ) of fig2 . as shown in ( d ) fig2 , the surface of the shaft without covering the photoresist 20 a , also referred to as an appeared surface of the shaft , is etched by an etchant . the photoresist 20 a is then stripped by a stripping agent to form a desirable groove pattern 12 . this embodiment is substantially the same as the eighth embodiment unless the photoresist is the negative photoresist . thus , the groove is formed on exterior surface of the shaft by etching . fig2 is a diagrammatic view illustrating steps for manufacturing a shaft according to a tenth embodiment of the invention , in which the shaft is shown in cross sectional view and is preferably made of cooper or alloys thereof . as shown in ( a ) of fig2 , the surface of the shaft 2 is coated by photoresist 20 a . in this embodiment the photoresist 20 a is a negative photoresist . as shown in ( b ) of fig2 , the shaft 2 is placed into a circular lamp 90 capable of emitting ultraviolet wavelength to expose the photoresist 20 a . a slice with a pressure - generating groove pattern is attached to an inner surface of the circular lamp 90 . then , the exposing is executed to photosensitive the negative photoresist corresponding to the transparent portion of the slice . in this embodiment , the slice is a mask 40 with pressure - generating pattern and an area where the pressure - generating groove 401 located is transparent . after exposing , the shaft is removed from the circular lamp 90 . a portion of the photoresist 20 a not photosensitized is cleaned by a developer to appear the surface of the copper shaft and form a groove pattern 401 corresponding to the groove pattern of the mask 40 , as shown in ( c ) of fig2 . as shown in ( d ) of fig2 , a deposited layer 80 is formed on the surface of the shaft without covering the photoresist 20 a , also referred to as an appeared surface of the shaft . the photoresist 20 a is then stripped by a stripping agent to form a desirable groove pattern 12 a between the two adjacent deposited layers 80 . while the invention has been described by way of example and in terms of preferred embodiment , it is to be understood that the invention is not limited thereto . to the contrary , it is intended to cover various modifications and similar arrangements ( as would be apparent to those skilled in the art ). therefore , the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements .