Abstract:
A micro-manipulator machine for harvesting and cryofreezing crystals for cryogenic storage and subsequent analysis includes a micropositioner mechanism for converting motions manually input to a position control knob to fractionally-scaled motions of a follower mechanism which includes a tool head support arm and tool head that releasably holds a filamentary polymer cryoloop for immersion into a liquid crystal growth media and extraction of a liquid drop containing a selected crystal from the media. A first automatic actuator mechanism orbits the tool head support arm, tool head, cryoloop, liquid drop and harvested crystal from a harvesting location to a retrieval location when the micropositioner input control arm has been moved manually away from the crystal harvesting location by the operator after extracting a crystal drop, and a second automatic actuator mechanism pivots the toll head into a flowing stream of a cryogenic gas to freeze the liquid drop and crystal.

Description:
BACKGROUND OF THE INVENTION 
     A. Field of the Invention 
     The present invention relates to apparatus used to facilitate the laboratory production of small organic crystals in the approximate size range of 10 microns or less. More particularly, the invention relates to a micropositioner machine for extracting or “harvesting” individual micron-size protein crystals from a liquid in which the crystals are grown, and cryofreezing and storing the extracted crystals for subsequent crystallographic analysis. 
     B. Description of Background Art 
     The development of new therapeutic drugs by medical researchers, particularly those containing biochemicals, has in recent times benefited from an energizing technology in which individual protein crystals having particular structural characteristics are grown and tested for therapeutic efficiency. This technology is useful because of the discovery that interactions between proteins and other biochemicals with living organisms depend not only on the chemical composition of a biochemical, but also upon its physical structure. Thus, many biochemical reactions at the cellular level proceed at an accelerated rate if biochemical and cellular sites have complementary shapes, e.g., analogous to a triangular peg having an appropriate shape and size for fitting into a triangular recess, or vice versa. Conversely, a mismatch between the structures of a cellular binding site and a biochemical characterized by non-complementary shapes, results in situations somewhat analogous to trying to fit a square peg into a round hole. In such cases, the reaction rate between a cell and a biochemical may be unacceptably low. 
     For the foregoing reasons, medical and biochemical researchers have devoted increased attention to techniques for producing individual crystals, such as protein crystals, which have specific shapes or other structural characteristics. 
     According to one technique for producing protein crystals with particular from which a crystal is to be grown, along with some sort of agent such as a fragment of a crystal of the type to be grown, to act as a seed for initiating crystallization from the liquid, which is sometimes referred to as a liquor. 
     Typically, protein crystals having selected structures are developed by growing individual crystals from liquid contained in small individual wells formed in the upper surface of a plate. Typical plates used for the cultivation of protein crystals are rectangularly shaped, flat plates which are several centimeters on a side. Each plate has a matrix, typically rectangularly shaped, of separate, individual wells. For example, a 96-well “sitting-drop” plate may have 96 wells, each capable of holding a one-micro liter drop of crystal growth solution. Another typical cell cultivating plate has 24 2-micro liter wells. 
     After each well in a crystal growth plate has been filled with a desired volume of a crystal growth cocktail, a predetermined time period is allowed to elapse to thereby enable growth of crystals in each cell. The crystal growth plate is then positioned in the field of view of a stereo microscope, as a first step in extracting or “harvesting” individual crystals by a human or robotic operator. 
     According to a presently employed method of harvesting individual protein crystals from crystal growth wells, a human operator uses an elongated pick-up tool holder which has a small diameter planar pick-up loop protruding from its end. The pick-up or “harvester” loop sometimes referred to as a “cryoloop” is removably attached to the tool holder, has a diameter in the range of about 0.05 mm. to 1 mm., and is typically made of a looped filament of nylon, etched Kapton, or other hydrophobic material, which has a typical diameter of about 10 micrometers. 
     With the aid of the microscope, the human operator looks into the liquid cocktail to determine if one or more crystals are present. If more than one are present, they may be attached to each other and therefore need to be separated. The separation may be accomplished manually using a very small knife blade. Alternatively, the knife blade may be mounted on the tool arm of the micro manipulator machine for finer position control to separate the crystals. 
     With the aid of the microscope, the human operator inserts the harvester cryoloop into a solution in a well in which the crystals are grown, at an oblique angle to encircle a crystal contained in the solution. The tool, with the cryoloop and an attached liquid drop containing a crystal suspended in the solution by surface tension of the liquid, is then withdrawn upwardly from the crystal growth well. 
     A final step in harvesting individual crystals includes freezing a cryoloop holding a liquid drop and a crystal by exposing the loop and drop to a stream of a cryogenic gas, such as nitrogen evaporated from liquid nitrogen. This action, referred to as cryocooling or cryofreezing, freezes the crystals, liquid and cryoloop together, whereupon the cryoloop is removed from the tool holder, and placed in a cryogenic storage compartment cooled by a cryogenic fluid such as a liquid nitrogen or liquid propane. 
     Individual cryoloops each containing a crystal are subsequently analyzed by X-ray diffraction methods to determine whether the crystal has desired structural properties. 
     Because of the small sizes of protein crystals and the drops of liquid from which they form, it can be readily appreciated that the task of harvesting and storing the crystals requires moving the cryoloop in very small, precisely controllable increments. Accordingly, it would be desirable to provide an apparatus which has a capability for precisely manipulating a small cryoloop to extract small liquid drops containing protein crystals from growth wells, and cryofreezing the loop, liquid drop and crystals en masse for subsequent X-ray diffraction analysis and processing. 
     A method of Operator-Assisted Harvesting Of Protein Crystals Using A Universal Micro Manipulating Robot was described in an article of that title appearing in the  Journal of Applied Crystallography  (2007) 40. pp. 539-545. The entire contents of that article, which are directed to a fully automatic crystal harvesting method, are incorporated by reference into the present application. 
     The present invention was conceived of in part to provide a micro-manipulator machine for crystal harvesting which could substantially enhance the speed and precision with which a human operator could perform harvesting and preservation of protein crystals from small individual crystal growth wells. 
     OBJECTS OF THE INVENTION 
     An object of the present invention is to provide a micro-manipulator machine for harvesting and cryofreezing crystals which facilitates manipulation of a tiny filamentary cryoloop tool to extract micro-liter size drops of liquid containing a selected crystal from micro-liter size crystal growth wells. 
     Another object of the invention is to provide a micro-manipulator machine for harvesting and cryofreezing crystals which includes a micropositioner mechanism that utilizes a manually operable input control arm coupled through a mechanical linkage mechanism to a follower mechanism on which is mounted a tool holder support arm having at a front outer end thereof a tool head for releasably holding a cryoloop useable for crystal harvesting, the linkage mechanism being so constructed as to cause the tool holder to move translationally in small fractions of displacements of a hand-manipulatable position control knob attached to the end of the control arm, thus enabling a cryoloop held in the tool holder to be precisely manipulated in motion increments which are fractional ratios of motions of the position control knob. 
     Another object of the invention is to provide a micro-manipulator machine for harvesting and cryofreezing crystals which includes a micropositioner mechanism that uses a pantograph-type motion divider mechanism for translationally moving a cryoloop at the tip of a tool head in coordinate displacements in a work space which are predetermined fractional ratios of translational motions in a control space input by hand motions of a human operator to a position control knob, and which includes a rotary actuator mechanism for rotating the tool holder arm to thus rotate a cryoloop at the end of the arm to adjustable inclination angles. 
     Another object of the invention is to provide a micro-manipulator machine for harvesting and cryofreezing crystals which includes a micropositioner mechanism that mechanically couples motions of a manually graspable position control knob at an input end of a motion control mechanism input control arm to a follower mechanism which has coupled thereto a tool arm and tool head that is moved translationally in co-ordinate directions in response to motions of the input position control knob, but at fractional ratios of displacements of the position control knob, and which includes a tool head angle control mechanism that enables the vertical inclination angle of a cryoloop held in the tool head to be remotely controlled by an angle control knob located on the input control arm near the position control knob. 
     Another object of the invention is to provide a micro-manipulator machine for crystal harvesting and cryofreezing crystals which includes a micropositioner mechanism for moving a tool head and protruding cryoloop in a work space above a work platform located remotely from a position control knob, in precisely scaled fractional ratios of motions of the position control knob in an input control coordinate space, and a rotary actuator mechanism for rotating the tool head and cryoloop to adjustable angles relative to a vertical axis through the tool holder and work table. Another object of the invention is to provide a micro-manipulator machine for harvesting and cryofreezing crystals which includes a micropositioner mechanism for translationally moving a tool head and cryoloop mounted therein in a work space above a work platform in response to movements of a remotely located position control knob, an angle control actuator responsive to movements by a human operator of an angle control knob coupled to an angle control encoder located near the hand control knob for adjusting an inclination angle of the tool head and cryoloop relative to a vertical axis of the work platform; and a tool arm support crank mechanism for orbitally moving the tool head and cryoloop upwards from the work platform towards a docking station and thus repositioning the tool head and cryoloop from a downwardly angled work orientation close to the work platform to a vertically upwardly oriented access position above the platform. 
     Another object of the invention is to provide a micro-manipulator machine for harvesting and cryofreezing crystals which includes a micropositioner mechanism for remotely positioning the translational position of the tip of a cryoloop held in a tool holder above a work platform, an angle control mechanism for controlling the inclination angle of the cryoloop, a tool arm support crank mechanism for orbitally moving the tool head and cryoloop upwards from the work platform towards a docking station, and thus positioning the tool head in an upwardly pointing orientation for removal and replacement of a cryoloop held within the holder, when the micropositioner mechanism has been used to move the tool head to an upward, horizontally centered location at which a docking arm protruding from the tool head support mechanism is proximate a docking site. 
     Another object of the invention is to provide a micro-manipulator machine for harvesting and cryofreezing crystals which includes a micropositioner mechanism for remotely controlling the vertical and lateral and fore-and-aft horizontal positions of a tool head holding a crystal harvester cryoloop, an angle control mechanism including a rotary actuator for controlling the inclination angle of the cryoloop relative to crystal growth wells in a plate placed on a work platform below the tool head, a docking station for contacting a docking arm of the micropositioner mechanism when the tool head has been moved upwards from a crystal growth well after the cryoloop has been inserted into a drop of liquid to thereby encircle and hold by surface tension a crystal, and retracted from the well, a tool arm support crank mechanism for orbitally moving the tool arm and head vertically upwards a substantial predetermined position above the work platform and proximate the docking station when the cryoloop has been withdrawn a predetermined distance upwards from the crystal growth well, and a pivoting mechanism for pivoting the tool head from an upward vertical orientation to an upward laterally inclined position to thereby displace a pivotable shutter from a position blocking a cryogenic gas stream for a selectable predetermined time period sufficient to enable cryogenic gas to freeze the liquid drop, crystals and cryoloop, the pivoting mechanism then pivoting the tool head to an upright vertical position to thus allow the pivotal shutter to return to a position blocking flow of cryogenic gas and enable removal of the cryoloop and frozen liquid drop and crystals for storage in a cryogenic storage area, and replacement of the removed cryoloop with a new cryoloop to enable subsequent crystal harvesting. 
     Various other objects and advantages of the present invention, and its most novel features, will become apparent to those skilled in the art by perusing the accompanying specification, drawings and claims. 
     It is to be understood that although the invention disclosed herein is fully capable of achieving the objects and providing the advantages described, the characteristics of the invention described herein are merely illustrative of the preferred embodiments. Accordingly, I do not intend that the scope of my exclusive rights and privileges in the invention be limited to details of the embodiments described. I do intend that equivalents, adaptations and modifications of the invention reasonably inferable from the description contained herein be included within the scope of the invention as defined by the appended claims. 
     SUMMARY OF THE INVENTION 
     Briefly stated, the present invention comprehends a micro-manipulator machine for harvesting and cryofreezing small crystals contained in small drops of liquid. 
     The machine according to the invention includes a manually operable micropositioner apparatus for remotely and precisely positioning the tip of a tool held in a tool head in a three-dimensional work space located above a tabular work platform which extends forward from a lower part of a front control panel of the machine. 
     In a preferred embodiment of a micro-manipulator machine for harvesting and cryofreezing crystals according to the present invention, the micropositioner apparatus includes an elongated, fore-and-aft disposed, generally horizontal input control arm coupled by a motion-dividing, pantograph-type bar-linkage coupler mechanism to a follower mechanism which supports a tool head support arm mount assembly. The tool head support arm mount assembly has protruding forward therefrom an elongated, straight tool head support arm which is parallel to the control arm, and protrudes forward through a central clearance opening in a front control panel of the machine that is located above and laterally displaced to the left of the control arm. The control arm protrudes forward of the front control panel, at a location offset to the right of the work platform. A tool head located at the front, outer end of the tool head support arm removably holds a tool, such as a cryoloop. 
     According to the invention, the linkage mechanism of the micropositioner is constructed so as to cause the cryoloop held in the tool holder to move translationally in three orthogonal directions in a three dimensional work space, motions of the cryoloop being predetermined fractional ratios of motions in a three-dimensional control space of a position control knob attached to the front end of the input control arm, the position control knob being manually manipulatable by a human operator. 
     According to the invention the tool head support arm, which preferably has a hollow tubular construction, protrudes forward in a generally horizontal direction from the tool head support arm mount assembly, and through the clearance opening through the front control panel of the machine. The tool head support arm is disposed coaxially through a tubular bearing support attached to the tool head support arm mount assembly. 
     An outer, front end of the tool head support arm has attached thereto an L-shaped tool head which holds a cryoloop. The tool head has a short, straight rear, longitudinally disposed leg fastened to the tool head support arm, and a short front transversely disposed leg which protrudes perpendicularly from the front end of the rear leg, and is thus disposed radially to the tool head support arm and lies generally in a vertical plane. 
     The front transverse leg of the L-shaped tool head has located in a transversely disposed outer end thereof a cylindrically-shaped socket for removably holding by magnetic force a cylindrically-shaped cryoloop support cap. The support cap has disposed axially inwardly from an outer frusto-conically shaped transverse face thereof a centrally located blind cryopin mounting bore. 
     The cryopin mounting bore is provided for receiving the inner end of a straight cryoloop pin which has protruding from an outer end thereof a small, planar cryoloop made of a thin filament of nylon, Kapton or the like. The plane of the loop is oriented generally parallel to the longitudinal axis of the cryoloop pin, and the cryoloop support cap is manually rotatable about its axis to orient the plane of the loop at selectable azimuth angles with respect to the co-linear axes of the outer, transverse leg of the tool holder, the cryoloop support cap and the cryoloop pin. As will be explained below, the cryoloop is used to extract or “harvest” a drop of liquid containing a crystal held in the liquid drop by surface tension, from individually selected wells of a crystal growth plate, by obliquely inserting the cryoloop into liquid in a well to encircle a selected crystal. The crystal is trapped in the cryoloop by surface tension, whereupon the cryoloop and liquid drop containing the crystal are withdrawn from liquid in a well. 
     The micro-manipulator machine for harvesting and cryofreezing crystals according to the present invention includes a rotary actuator mechanism for orbitally moving the tool head support arm and rotating the arm about its longitudinal axis to thus pivot the transverse output leg of the tool head and attached cryopin to various orbital angles relative to the tool head support arm, thus adjusting the vertical inclination angle of the cryoloop relative to a crystal growth well. The rotary actuator mechanism includes a rotary stepper motor coupled through a C-shaped yoke crank to a rear, inner end of the tool head support arm at a location behind the front panel of the machine and within an enclosure, rotation of the crank causing orbital motion of the tool arm. 
     The micro-manipulator machine according to the invention also includes a rotatable cryoloop inclination-angle control knob mechanically coupled to a shaft-angle encoder, which is in turn coupled electrically through machine control electronics to the tool support arm stepper motor. In a preferred embodiment, the cryoloop inclination-angle control knob and shaft-angle encoder are mounted on a front, outer end of the input control arm, near the position control knob. 
     According to the invention, the machine control electronics is configured to enable remote adjustment of the cryoloop inclination angle to a desired value, and includes a cryoloop Tool Angle Save control switch located on the front panel of the machine for storing that value. This arrangement enables an operator to rotate the cryoloop angle control knob to thus remotely adjust the inclination angle of the tool head and a cryoloop held in the tool head, relative to the upper horizontal surface of the work platform, which protrudes horizontally forward from a lower front portion of the machine. 
     Rotational adjustment of the tool head enables the operator to adjust the inclination angle of a cryoloop held in the tool head relative to a liquid drop in a selected one of an array of crystal growth wells in the upper surface of a crystal growth plate placed on the work platform. By operating the Tool Angle Save switch on the front panel of the machine, the cryoloop inclination angle data is saved in electronic memory so that positioning the cryoloop into a downward position above the work table will automatically restore the inclination angle of the cryoloop to a preset, saved value stored in memory. 
     The micro-manipulator machine according to the present invention includes a tool arm support crank mechanism for semi-automatically moving the tool arm a relatively large vertical distance above the work platform after the micropositioner has been used to manipulate the tool head in precisely controllable small translational motions to thus extract a liquid drop and crystals from a well. 
     The tool arm support crank mechanism includes a crank having the shape of a C-shaped yoke which has a pair of parallel front and rear vertically disposed arms which depend perpendicularly outwards from a longitudinally disposed upper base bar of the yoke. The front and rear arms have located between inner facing vertical sides thereof a rectangularly-shaped space in which is located a stepper motor. The stepper motor, which is attached to the front portion of a tool head support arm support mount assembly plate, has generally a cylindrical shape and a fore-and-aft disposed armature shaft which is parallel to the base bar of the crank yoke. 
     The rotatable shaft of the stepper motor is attached at the rear end thereof to the outer, lower end of the rear crank yoke arm. The rear end of the tool head support arm has a rearwardly extending coaxial shaft extension which is rotatably supported by front and rear longitudinally aligned bearings in the longitudinally disposed upper base bar of the crank yoke. 
     The tool head support arm has mounted coaxially thereon a cam wheel located forward of the front crank yoke arm. The front transverse leg of the tool head and cryoloop mounted therein are resiliently biased to be held in parallel alignment with the front and rear yoke arms by a cam follower button which is mounted to the front yoke arm and urged into a depression in the cam wheel by a leaf spring attached to the front yoke arm. 
     The tool arm cam and spring arrangement maintains the front transverse leg of the tool head and a cryoloop held in the tool head in parallel alignment with front and rear transversely disposed legs of the crank yoke. Thus, the cryoloop inclination angle is controlled by the rotational angle of the stepper motor armature shaft but is rotatable with respect to the yoke arm to enable the tool head and cryoloop to be pivoted momentarily towards a cryofreezer station, to thus allow cryogas to impinge on a liquid drop held in the cryoloop. The pivot mechanism which enables this action includes a transversely disposed pinion gear attached to the rear end of the shaft extension of the tool head support arm, the shaft extension being longitudinally disposed through front and rear aligned support bearings located in front and rear longitudinally aligned locations of the longitudinally disposed crank yoke base bar. 
     The tool head pivoting mechanism includes a convex transversely disposed sector gear which protrudes vertically upwards from the cylindrical housing of the stepper motor. The sector gear has longitudinally disposed teeth and grooves located on a circular arc segment, and is vertically centered on a longitudinally disposed vertical center plane of the stepper motor housing. The teeth of the sector gear, which has an arc length of about 20 degrees, are transversely aligned with the teeth of the pinion gear attached to the rear shaft extension of the tool head support arm. 
     The tool head orbiting and pivoting mechanisms of the rotary actuator mechanism function as follows. 
     After the micro manipulator mechanism has been used to withdraw a liquid drop from a crystal growth well by precise, small translational motions of the tool head in response to motions of the manually operated micropositioner position control knob, the operator manipulates the micropositioner position control knob to thus move the cryoloop a larger, vertical distance above the work platform. At a predetermined vertical distance, an electro-optical sensor attached to the miropositioner follower mechanism is actuated and sends a signal to control electronics. In response to this signal, the control electronic outputs a drive signal to the stepper motor. The stepper motor then rotates the yoke crank through a predetermined counterclockwise angle sufficient for the tool head and cryoloop to be orbited counterclockwise from a lower right-hand, harvesting location to an upper left docking location. Orbital motion of the yoke crank also causes the tool head and cryoloop to be repositioned from a downwardly angled orientation to a vertically upward orientation. 
     The operator then manipulates the position control knob to move the tool arm a further short distance upwardly and to the left, and then downwards until a perceptible physical contact is made between a docking arm protruding obliquely from the tool arm support assembly and an electrical switch located on the docking station fixedly attached to a stationary support plate of the machine. 
     Actuation of the docking station switch causes the control electronics to send a signal of a predetermined, selectable time duration to the stepper motor. That signal causes the stepper motor shaft to rotate a small additional counterclockwise angular increment, i.e., about 20 degrees, causing the pinion and sector gears to mesh, and thereby causing the tool head to tilt or pivot about 20 degrees counterclockwise. This action in turn causes a cam follower roller mounted on the tool head arm at the outer radial end of a bracket located rearward of the front transverse leg of the tool head to push leftwards against a cam bar protruding from the right side of a pivotable cryogas shield shutter. This motion in turn causes the cryofreeze shutter to pivot away from a position obstructing flow of cryogas for a predetermined period, thus enabling flow of cryogas onto the cryoloop and liquid drop for the predetermined time period. At the end of the time period, the stepper motor shaft is rotated 20 degrees clockwise to its previous position, in which the tool head and cryoloop are vertically upwardly oriented. Clockwise motion of the tool head enables the cryofreeze shutter to return to a rest position in which flow of cryogenic gas is blocked. In the upright vertical position, the cryopin and cryoloop may be removed by the operator and placed in cryostorage. 
     The micro-manipulator machine according to the present invention includes a stereoscopic microscope which protrudes from an upper front part of the machine, the microscope having a pair of objective lenses which are positionable at adjustable distances above the center of the work platform. By viewing a crystal growth plate through the stereo microscope, a human operator may manipulate the position control knob to thus remotely position a cryoloop above a selected crystal growth well in the upper surface of the plate, move the tool head downwards to thus insert the cryoloop at a selected inclination angle into a liquid drop containing crystals located in the well, and retract the tool head upwards to thus withdraw a crystal-containing liquid drop adhered to the loop by surface tension from the well. 
     In a preferred embodiment of the invention, the work platform has a flat upper surface which has a centrally located light-transmissive window below which is located an adjustable intensity light source. Also, the platform preferably includes a jack mechanism that enables the height of the platform to be adjusted relative to a base plate of the machine supported by a laboratory bench or table top on which the machine is placed. This arrangement facilitates viewing and manipulating crystals in drops located in the wells of transparent crystal growth plates of various heights. 
     The micro-manipulator machine according to the present invention also includes a cryofreezer apparatus for cryofreezing en masse a cryoloop and crystal-containing liquid drop, to thereby preserve crystals for subsequent crystallographic analysis, as will now be described. 
     According to the invention, the micro-manipulator machine is provided with a cryofreezer station located above and offset to the left of the center of the work platform. The cryofreezer station includes a hollow cryogas supply tube which is located above the left side of the work platform, and protrudes to the right. A continuously flowing supply of a cryogenic gas such as cold nitrogen gas evaporated from a tank of liquid nitrogen is conveyed through the cryogas supply tube from a cryogas supply apparatus. 
     The cryofreezer station includes a shutter mechanism that has a generally vertically disposed shutter or shield plate attached to the right-hand end of a shutter arm, which is pivotably mounted to the transversely disposed, vertical outer face of the shutter arm. The shield plate includes a vertically disposed shutter blade mounted perpendicularly to the laterally inwardly located right-hand end of the shutter arm, which is biased by the weight of a portion of the arm located to the left of the pivot axis of the arm, to a horizontally disposed orientation. In that position, the shield plate obstructs lateral flow of cryogenic gas. 
     The shutter mechanism according to the invention includes a curved cam bar which protrudes rightward from the shutter plate. In response to a counterclockwise pivotal motion of about 20 degrees of the cryoloop support tool head, the tool head cam follower roller pushes against the cam bar, thus causing the cryofreezer shutter arm to rotate a corresponding angular increment in an opposite, clockwise sense. Pivotal rotation of the shutter plate causes it to move downwards from an upper position in which a stream of cold nitrogen gas is obstructed from flowing to the right, to a lower position which allows a stream of cold nitrogen gas to contact the cryoloop, which is tilted about 2 degrees counterclockwise into the stream, thus freezing the cryoloop, liquid drop and a crystal contained therein. 
     According to the invention, the cryoloop support tool head remains tilted to expose the cryoloop to the flowing cryogenic gas for an operator-preselected period of time, e.g., 0.2 second to 4 seconds or longer if required, sufficient to freeze the liquid drop, crystal and cryoloop en masse. 
     The micro-manipulator machine according to the present invention is so constructed as to facilitate semi-automatic operation of the cryofreezer mechanism. Thus, the machine includes a switch located at a docking site of the tool holder support arm, which outputs a signal to the control electronics, which in turn outputs a 2-degree tilt command signal to the rotary actuator of the tool head support arm. 
     The docking site switch, which is attached to a docking station fixed to the machine support structure located behind the front control panel of the machine, is actuated by contact with a docking arm which protrudes obliquely from the tool support arm, when the arm has been moved upwardly, to the left, and down slightly. 
     When the tool head support arm has been moved upwards from the work platform sufficiently to withdraw a cryoloop and liquid drop from a crystal growth well a predetermined distance, a tool arm height sensor outputs a signal to the control electronics which outputs a command signal to the tool head rotary actuator mechanism to orbit the tool head to an upper left location, at which location the tool head and cryoloop are vertically upwardly oriented. Then, when the input control arm is manipulated to thus move the tool support arm a small distance upwards and to the left, to thus position the cryopin and cryoloop adjacent to the shutter cam bar, a slight downward motion of the position control knob causes the docking arm to move downwards and thus contact the docking site switch. Contact of the docking arm with the docking site switch produces a command signal to the stepper motor driver of the rotary head actuator to tilt the tool head counterclockwise, pivoting the cryofreezer shutter clockwise to an unblocking position enabling flow of cryogenic gas to thus expose the cryoloop to flowing cryogenic gas for an operator-preselected time interval, as described above. 
     After expiration of the preselected time interval, the rotary actuator automatically pivots the tool head clockwise back to an upright vertical position, enabling the cryofreeze shutter to pivot counterclockwise to an orientation in which the cryofreeze shutter blocks flow of cryogenic gas. At this position, the cryopin, cryoloop and frozen liquid drop and crystal may be manually removed from the tool head, and placed in a cryogenic storage container. A new cryopin and cryoloop may then be inserted into the cryopin support cap, to enable harvesting new crystals. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front perspective view of a micro-manipulator machine for harvesting and cryofreezing crystals according to the present invention, showing an enclosure cover panel thereof removed. 
         FIG. 2  is a fragmentary front elevation view of the machine of  FIG. 1 , showing a stereo-microscope thereof removed. 
         FIG. 3  is a right-hand upper perspective view of the machine of  FIG. 1 , showing an upper enclosure cover panel thereof removed. 
         FIG. 4  is a fragmentary rear perspective view of the machine of  FIG. 1 . 
         FIG. 5  is a left-hand upper perspective view of the machine of  FIG. 1 . 
         FIG. 6  is an electrical block diagram of the machine of  FIG. 1 . 
         FIG. 7  is a front perspective view of the machine of  FIG. 1 , showing a tool arm and tool head thereof moved to an upper, upright location to enable placement of a crystal growth plate on a work platform of the machine, and enable installation of a cryoloop in the tool head. 
         FIG. 8  is a fragmentary, partly diagrammatic front perspective view of the machine of  FIG. 1 , showing the manner of installing and orienting a cryoloop pin and support cap in the tool head of the machine. 
         FIG. 9  is a view similar to that of  FIG. 8 , showing a tool head support arm and tool head of the machine moved downwards towards the work platform of the machine, preparatory to using a cryoloop installed in the tool head to extract crystals from crystal growth wells in a crystal growth plate placed on the work platform. 
         FIG. 10  is a view similar to that of  FIG. 9 , showing the adjustability of the vertical inclination of the tool head, preparatory to inserting the cryoloop into a selected well to harvest a liquid drop containing crystals. 
         FIG. 11  is a view similar to that of  FIG. 10 , showing the tool arm and tool head moved upwards from the platform towards a docking station of the machine, after withdrawing a liquid drop containing crystals from a crystal growth well. 
         FIG. 12  is a view similar to that of  FIG. 11 , showing the tool head momentarily pivoted counterclockwise to thus rotate a cryoshutter clockwise and thereby enable a stream of cryogas to impinge on the liquid drop held in the cryoloop. 
         FIGS. 13-15  are fragmentary, partly diagrammatic rear perspective views of a tool arm orbital yoke crank and tool head pivot mechanism, showing the disposition of the mechanisms for the tool head orientations shown in  FIGS. 10-12 , respectively. 
         FIG. 16  is a fragmentary right-side elevation view of the machine of  FIG. 1 , showing the micro-manipulator control arm and follower thereof in a lower-most, right-most dispositions, and showing in phantom upward triggering dispositions, of the control arm and follower. 
         FIG. 16A  is a view similar to that of  FIG. 16 , but showing tool arm components of the machine removed for clarity. 
         FIG. 17  is an upper plan view of the arrangement of  FIG. 16 . 
         FIG. 17A  is a view similar to that of  FIG. 17 , but showing tool arm components of the machine removed for clarity. 
         FIG. 18  is a view similar to that of  FIG. 16 , but showing the control arm and follower in an uppermost and leftward disposition. 
         FIG. 18A  is a view similar to that of  FIG. 18 , but showing tool arm components of the machine removed for clarity. 
         FIG. 19  is an upper plan view of the arrangement of  FIG. 18 . 
         FIG. 19A  is a view similar to that of  FIG. 19 , but showing tool arm components of the machine removed for clarity. 
         FIG. 20A  is a fragmentary view of the machine of  FIG. 1 , partly in longitudinal section, showing a tool head support arm and tool head thereof orbited downwards and rightwards to position a cryoloop held in the tool head is proximity to a work platform of the machine, in a crystal harvesting position. 
         FIG. 20B  is a fragmentary front elevation view of the arrangement of  FIG. 20A , showing a tool angle biasing cam and follower spring thereof. 
         FIG. 21A  is a view similar to that of  FIG. 20A , but showing the tool head support arm and tool head oriented to an upper left position. 
         FIG. 21B  is a fragmentary front elevation view of the arrangement of  FIG. 20A , showing the disposition of the tool angle biasing cam and follower spring rotated counterclockwise as viewed from the front of the machine. 
         FIG. 22  is a fragmentary sectional view of the tool arm support head and tool head, and cryoloop pin of the machine of  FIG. 1 , showing an optional vacuum tube accessory thereof. 
         FIG. 23  is a fragmentary right side perspective view of the machine of  FIG. 1 , with the tool arm and tool head thereof oriented in and positioned at a lower, crystal harvesting location, as shown in  FIG. 10 . 
         FIG. 24  is a view similar to that of  FIG. 23 , showing the tool arm and tool head thereof oriented and positioned at an upper, crystal retrieval position, as shown in  FIG. 11 . 
         FIG. 25  is a fragmentary front perspective view of the machine of  FIG. 1 , showing the tool arm and tool head moved towards a docking station, corresponding to the orientation of the tool head shown in  FIG. 11 . 
         FIG. 26  is a fragmentary front perspective view of the machine of  FIG. 1 , on an enlarged scale and showing contact of docking arm thereof with a docking station. 
         FIG. 27  is a fragmentary front perspective view of the machine of  FIG. 1 , showing the tool arm and tool head thereof oriented as shown in  FIG. 12 , showing the tool head automatically and momentarily pivoted counterclockwise to thus expose the tool head to flowing cryogas. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1-27  illustrate various aspects of the structure and functions of a micro-manipulator machine for harvesting and cryofreezing crystals according to the present invention. The machine according to the present invention includes a micropositioner apparatus manually operable by a human operator to precisely position a remotely located tool head holding a cryoloop used for crystal harvesting. 
     The micropositioner apparatus includes an input control arm which protrudes forward from the right side of the machine, and which is terminated at an outer, front end of the control arm by a hand-graspable position control knob. 
     The micropositioner apparatus contains a mechanical linkage mechanism which causes a tool head holding a cryoloop to move translationally in orthogonal directions in a three-dimensional work space located above a work platform in precise fractional ratios of movements of the position control knob in a remotely located command input control space. The micropositioner thus enables a cryoloop mounted in the tool head to be remotely manipulated to thus insert the cryoloop into a selected one of a plurality of small crystal growth wells in a crystal growth plate supported on the work platform, retract the cryoloop from the well with a liquid drop containing a selected crystal, and move the cryoloop upwardly and to the left to a docking station and cryofreezer station comprising part of the machine. 
     A suitable micropositioner apparatus for use in the machine of the present invention is a modification of the “Micropositioner For Ultrasonic Bonding” described in U.S. Pat. No. 5,871,126. The entire disclosure of that patent is hereby incorporated by reference into the present disclosure. 
     Referring first to  FIGS. 1-5 , it may be seen that a micro-manipulator machine  30  for harvesting and cryofreezing crystals includes a laterally elongated, rectangular rear base plate  31  which supports a micropositioner  32  and other components of the machine. The machine  30  includes a front rectangular base plate  33  of a size and shape similar to that of rear base plate  31 . The front base plate protrudes forward from a front vertical wall  34  of the rear base plate, and has a horizontal upper surface  35  parallel to upper surface  36  of the rear base plate. 
     Machine  30  includes a work platform  37  which has a size and outline shape similar to that of front base plate  33 . Work platform  37  has a flat, horizontal upper work surface  38  which overlies upper surface  35  of front base plate  33 , at a height controllable by a height adjustment knob  39 , which protrudes forward from front edge wall  40  of the front base plate. The height adjustment knob  39  is coupled through a shaft (not shown) to a work platform elevator jack (not shown) located between the lower surface  43  of the work platform and the upper surface  35  of the front base plate. 
     As shown in  FIGS. 1 and 2 , work platform  37  of machine  30  has located in a central circular aperture  45  through its thickness dimension a circular light-transmissive diffuser window  46 , an upper flat surface  47  of which is flush with upper surface  38  of the work platform. Machine  30  includes a light source  48  below window  46  which is connected to an electrical power source through an intensity control rheostat  49  mounted on a right vertical side plate  50  of work platform  37 . 
     Referring still to  FIGS. 1-6 , it may be seen that machine  30  includes a laterally elongated, rectangular front control panel  51  which extends perpendicularly upwards from a junction plane between rear vertical edge wall  44  of front base plate  33  and the front vertical edge wall of rear base plate  31 . As shown in  FIG. 3 , front control panel  51  has a short vertical lower base portion  52  and a longer, rearwardly angled upper portion  53 . 
     As shown in  FIGS. 1-5 , micropositioner apparatus  32  includes a generally horizontally disposed input control arm  55  which protrudes forward from an outer, right-hand end of a generally laterally disposed straight beam component  56 A of a parallelogram linkage bar assembly  56  of the micropositioner apparatus. As shown in the figures, lateral beam  56 A has a rectangular cross-sectional shape, and a skeletonized construction. 
     The parallelogram linkage bar assembly  56 , which is also generally horizontally disposed, protrudes laterally outwardly towards the right from an opening  58  in a right-side of machine  30 , above rear base plate  31 . Thus, input control arm  55  is disposed in a generally fore-and-aft direction in a horizontal plane, offset to the right of right-hand side wall  59  of machine  30 . As shown in the figures, input control arm  55  has the shape of a long straight shaft which is terminated at a front, free end thereof by an axially mounted, spherically-shaped position control knob  57 . 
     Referring to  FIGS. 3 ,  4  and  17 A, it may be seen that an inner, output end  60  of lateral beam  56 A parallelogram bar linkage assembly  56  of micropositioner apparatus  32  is pivotably coupled through a follower mechanism  61 , tool head support arm support plate  62  and orbital actuator mechanism  101  including a yoke crank  102  to an elongated, straight, generally horizontally disposed tool head support arm  63  which protrudes forward through a rectangularly-shaped tool-head support arm clearance aperture  64  that is laterally centrally located in upper part  53  of front control panel  51 . Thus, tool head support arm  63  is disposed in a generally fore-and-aft direction, above and parallel to upper surface  38  of work platform  37 , and parallel to input control arm  55 . 
     As shown in  FIGS. 16A-19A , a laterally inwardly located end  60  of micropositioner lateral beam  86  is pivotably supported by the right-hand face of a vertical support plate  72 , which protrudes upwardly from rear machine base plate  31 . 
     As may be seen best by referring to  FIGS. 20A and 20B , tool head support arm  63  has disposed axially rearward therefrom an elongated, straight tool head support arm shaft extension  66 . The support shaft extension  66  has fastened coaxially to a rear end portion thereof a pinion gear  67 , the function of which will be described below. As will be described in detail below, yoke crank  102  is rigidly coupled to the output shaft  70  of a stepper motor  71 . In response to electrical drive signals received from a control electronics module  72 , stepper motor  71  incrementally rotates crank yoke  102  and tool head support arm  63 . 
     As shown in  FIGS. 1-6 , and  22 , tool head support arm  63  has fastened to a front, outer end thereof an L-shaped tool head  73 . Tool head  73  has a short, straight, rear longitudinally disposed leg  74  which is axially aligned with and fastened to a front, outer end of tool head support arm  63 . Tool head  73  also has a short, straight front transversely disposed leg  75  which depends perpendicularly from the front end of rear leg  74 , i.e., in a radial direction relative to tool head support shaft  66 . Thus, front leg  75  is disposed generally in a vertical plane, and is pivotable in that plane by rotation of tool head support arm  63 . 
     As shown in  FIGS. 7 ,  8 ,  22  and  25 , the front radially disposed leg  75  of tool head  73  has located in a transversely disposed outer end face  76  thereof a coaxially centrally located, blind socket  77  for removably holding by magnetic force provided by a magnet  78  (not shown) a cylindrically-shaped cryoloop support cap  79 . The cryoloop support cap  79  has disposed axially inwardly from an outer frusto-conically-shaped transverse face  80  thereof a central coaxial bore  81 . Bore  81  is provided for receiving the inner end portion of the shank  82  of straight cryoloop pin  83 . Cryoloop pin  83  has protruding from an outer transverse end  84  thereof a small, planar cryoloop  85 . 
     Cryoloop  85  consists of a thin filament of nylon, Kapton or other polymer, which is formed into a longitudinally elongated oval-shaped planar loop, opposite ends of the filament being arranged in a parallel, twisted configuration and inserted into a coaxial bore  86  extending longitudinally inwards into outer transverse face  84  of cryopin  83 . The filament diameter of a typical cryoloop  85  is about 10 microns, while the loop diameters range from about 0.05 mm to about 1.0 mm. 
     In an example embodiment of machine  30  that was tested by the present inventor, the cryoloop support cap  79 , cryoloop pin  83  and cryoloop  85  were obtained from the Hampton Research Corporation, 34 Journey, Aliso Viejo, Calif. 92656-3317. In the example embodiment, a pickup tool  87  consisting of Hampton Research Catalog No. HR4-747 cryoloop support cap  79  to which is permanently attached a threaded and bonded, solid 3 mm diameter copper cryoloop pin  83  was used. Bore  86  of cryoloop pin  83  had a diameter of about 0.65 mm, and was adapted to insertably receive a Cat. No. HR4-981 cryoloop  85 . As will be described below, the pickup tool  87  is used to harvest crystals by inserting the cryoloop  85  at the end of the fool into a well containing a liquid drop and crystals. 
     As shown in  FIGS. 1-7 , machine  30  includes a tool head angle control mechanism  90  for remotely adjusting the axial rotation angle of tool head support arm  63 , and hence the vertical inclination angle of a cryoloop  85  held parallel to front transverse leg  75  of tool head  73 . The tool head cryoloop vertical inclination angle control mechanism  90  includes an electrical shaft angle encoder  91  which has protruding therefrom a shaft terminated at an upper end thereof by a, conically-shaped control knob  92 . The encoder  91  is mounted on an encoder support block  93 , the latter being longitudinally slidably mounted on micropositioner input control arm  55 . 
     As shown in the figures, shaft angle encoder support block  93  has a bifurcated clevis-like shape which includes front and rear laterally outwardly protruding front and rear arms  94 F,  94 B, which have therethrough front and rear longitudinally aligned bores  95 F,  95 B that are slidably mounted on control arm shaft  55 . A toggle clamp bar  96  located between front and rear arms  94 F,  95 B enables encoder support block  93  to be slid rearward of front micropositioner position control knob  57  to a desired position by a human operator, and locked in that position by pivoting toggle clamp bar  96  downwards. 
     In response to manual twisting of tool angle encoder knob  92 , shaft angle encoder  91  outputs an electrical signal through a flexible electrical cable  97  to control electronics module  98 . As shown in  FIG. 6 , control electronics module  98  contains circuitry  99  which outputs stepper motor drive signals to tool head support shaft stepper motor  71 , which are effective in orbiting tool head support arm  63  and tool head  73  to selected rotation angles and thereby orient the tool head and cryoloop to selected vertical inclination angles. 
     As shown in  FIGS. 1 and 7 , machine  30  includes a Tool Angle Save switch  88  mounted on font control panel  51  of the machine, and a Cryofreeze Time Duration digiswitch  89  also mounted on the front control panel. Both switches are electrically connected to control circuitry  99  in control electronics module  98 , the functional operations which will be described below. 
     Referring to  FIGS. 4 ,  20 A,  21 A and  24 , it may be seen that micro manipulator machine  30  includes a tool arm support crank mechanism  101  for semi-automatically orbitally moving the tool arm. Crank mechanism  101  is effective in orbitally moving the tool head  73  and cryoloop  85  from a downwardly inclined, crystal harvesting location as shown in  FIG. 1 , to a docking site location above and to the left of the center of the machine, as shown in  FIG. 25 . 
     As shown in  FIGS. 4 ,  20 A,  21 A and  24 , tool arm support crank mechanism  101  includes a crank  102  having the shape of a C-shaped clevis or yoke which has front and rear vertically disposed parallel arms  103 ,  104 , which depend perpendicularly from a longitudinally disposed base bar  105  of the yoke. The front and rear yoke arms  103 ,  104  have located between inner facing vertical sides  106 ,  107  thereof a rectangularly-shaped space  108  in which is located a stepper motor  71 . Stepper motor  71  is attached to the upper surface  110  of tool head arm support mount assembly plate  62 , near a front transverse end  112  of the plate. Stepper motor  71  has a generally cylindrically-shaped housing  113  and a longitudinally disposed armature shaft  70  which is disposed parallel to base bar  105  of crank  102 . 
     Shaft  70  of stepper motor  71  is connected a rear end  115  thereof to the inner, upper end  116  of rear yoke arm  104  of crank yoke  102 . The rear shaft extension  66  of tool head support arm  63  is rotatably supported by front bearing  118  which extends inwards from the front surface  119  of front crank yoke upper base bar  105 . 
     Reduced diameter rear shaft extension  66  of tool head support arm  63  is coaxially aligned with the tool arm, and protrudes axially rearwards from rear surface  121  of the tool arm. The rear end of tool arm shaft extension  66  is rotatably supported by a rear bearing  120 . Tool arm shaft extension  66  has mounted coaxially at the front end  122  thereof a rotary cam wheel  123  which is adjacent to the front surface  119  of crank upper base bar  105 . 
     Front transverse leg  75  of tool head  73  and a cryoloop  85  mounted in the leg are resiliently biased to be held in parallel alignment with the front and rear yoke arms  103 ,  104  by the following construction. 
     As shown in  FIGS. 13 through 15  and  20 A- 21 B, machine  30  has a cam follower  124  which includes a leaf spring  125  that is mounted on front crank yoke arm  103 . Leaf spring  125  has a flat, elongated rectangular shape and is fastened at a lower end thereof to front crank yoke arm  103 , near a radially outwardly located end of the arm. As shown in  FIG. 13-15 , leaf spring  125  has flat, parallel outer and inner surfaces  127 ,  128 , which are disposed parallel to a fore-and-aft plane, i.e., perpendicular to front surface  103 A of front yoke arm  103 . 
     Leaf spring  125  is attached to an outer end of front yoke arm  103  by means of a rectangularly-shaped spring mounting block  129  which protrudes forward from front surface  103 A of the arm, near the radially outwardly located face  130  of the arm, and a screw  131  which is disposed through hole  132  through the lower end of the leaf spring, and tightened into a threaded bore  133  which penetrates an outer face  134  of the spring mounting block. 
     Referring to  FIGS. 13 through 15 , it may be seen that leaf spring  125  has protruding laterally inwards from an upper free end thereof a rounded follower knob  126  which is urged resiliently into a concave depression  136  in the outer peripheral surface  137  of cam wheel  123 . 
     The cam and follower spring arrangement described above resiliently biases the tool head support arm shaft angle so that the front transverse leg  75  of tool head  73 , and a cryoloop held in the tool head are in alignment with the longitudinal axes of front and rear transversely disposed legs  103 ,  104  of crank yoke  102 . Thus, the inclination angle of a cryoloop  85  held in tool head  73  may be adjusted by adjusting the orbital angle of yoke crank  102 , which is in turn adjusted by the azimuth or rotation angle of armature shaft  70  of stepper motor  71 . However, as will be described below, the cam and spring arrangement comprise parts of pivot mechanism  138  which enables tool head arm  63  and attached tool head  73  and cryoloop  85  to be pivoted momentarily away from parallel alignment with the front arm  103  of yoke angle  102 , against biasing tension provided by spring  125 . As will also be described below, pivot mechanism  138  of tool head support arm  63  enables the tool head arm and head  73  to be pivoted momentarily towards a cryofreezer station  139 , to thus allow cryogas to impinge on a liquid drop held in a cryoloop. 
     Referring to FIGS.  4  and  13 - 15 , it may be seen that tool head pivot mechanism  138  includes a transversely disposed sector gear  140  which protrudes vertically upwards from an outer cylindrical surface  141  of housing  142  of stepper motor  71 . Sector gear  140  has longitudinally disposed teeth  142  and grooves  143  located on a circular arc segment, and is vertically centered on a longitudinally disposed center plane of the stepper motor housing. The teeth of the sector gear  140 , which has an arc length of about 20 degrees, are transversely aligned with the teeth and grooves  144 ,  145  off pinion gear  69  attached to the rear end of tool head arm support shaft  66 . As shown in  FIGS. 16-22 , tool head arm support shaft  66  is disposed longitudinally rearwards through front and rear longitudinal bearings  146 ,  147  in yoke crank base bar  106 . Thus, as will be described below, when stepper motor shaft  70  is rotated counterclockwise sufficiently far for pinion gear  69  to contact the right side of sector gear  140 , further counterclockwise rotation of the stepper motor shaft will cause the pinion gear and sector gear to mesh, thus causing tool arm support shaft  66  to rotate against the tension provided by cam and follower spring  123  and  125 . 
     Referring again to  FIGS. 1-5 , it may be seen that machine  30  according to the present invention includes a stereoscopic microscope  150 . As shown in  FIGS. 1 and 3 , stereoscopic microscope  150  is laterally centrally located with respect to work platform  37  of machine  30 , and has a lower generally frusto conically-shaped objective lens turret  151  which is positioned in axial alignment above central light transmissive diffuser window  46  of the work platform. 
     Objective lens turret assembly  151  of stereoscopic microscope  150  fits vertically downwards into a cylindrical bore  152  provided through a horizontally disposed rectangular-shaped support plate  153  which forms the outer leg  154  of an inverted L-shaped microscope support bracket  155 . An inner vertical leg  156  of microscope support bracket  155  is coupled through a rack-and-pinion elevator mechanism  157 , adjustable in height by a hand wheel  158 , to an obliquely upwardly and forwardly angled cantilever support bar  159 . The latter has a flat, horizontally disposed lower surface  160  which is fastened in flat overlying contact to the flat upper surface  161  of flat, horizontally disposed microscope mounting plate  162  which protrudes rearward from a rear inner wall  163  of front control panel  53 , the upper surface  161  being coplanar with the upper edge  164  of the front control panel. 
     Referring to  FIGS. 1 and 3 , it may be seen that stereoscopic microscope  150  includes an ocular head structure  165  which has a cylindrically-shaped lower housing  166  that is coaxially aligned with lower objective lens turret  151 . Housing  166  has a lower, flat, annular ring-shaped shoulder flange  167  which joins the upper end of lower objective lens turret  151 , which is supported by the flat upper surface  168  of support plate  153 . 
     As shown in  FIGS. 1 and 3 , ocular head structure  165  of stereoscopic microscope  150  has disposed forward from an upper end of a lower cylindrically-shaped housing  166  a box-shaped eyepiece mounting assembly  169 . The latter has a flat, horizontally disposed upper wall surface  170 , and a flat transversely disposed front rectangularly-shaped lens mount surface  171  which is disposed parallel to but angled downwardly from the upper wall surface. A pair of left and right eyepiece holder tubes  172 L,  172 R protrude perpendicularly upwards from the downwardly angled front lens mount surface  171 . Eyepiece holder tubes  172 L,  172 R hold ocular lens assemblies  173 L,  173 R, respectively, which are individually adjustable to compensate for differing focus distances of the left and right eyes of a human operator. 
     As shown in  FIG. 1 , stereoscope microscope  150  also includes a focus control hand wheel  174  which protrudes from a right side wall  175  of the microscope, and which is used to bring into focus an image of a cryoloop  85  and a selected well  176  in the upper surface  177  of a crystal growth plate  178  placed on light transmissive window  46  of work platform  37 . 
     As shown in  FIGS. 25 and 27 , machine  30  includes a cryofreezer apparatus  180  for cryofreezing en masse a cryoloop and a liquid drop containing a crystal held within the cryoloop. 
     Referring to  FIGS. 11 ,  12 ,  25 , and  27 , it may be seen that cryofreezer apparatus  180  includes an elongated rectangular cross section shutter support beam  181 . Cryofreezer apparatus includes a source of liquid nitrogen  182  from which is boiled off cold nitrogen gas, which is input to a hollow, laterally disposed flexible cryogas supply tube  183 . The latter is connected at a rear input end thereof located behind front machine control panel  51  to a source ( 184 , not shown) of a cryogas, such as nitrogen gas evaporated from liquid nitrogen. Cryogas supply tube  183  extends from source  182 , horizontally towards the right, i.e., towards a vertical center plane of work platform  37 . An example of a suitable source  182  of cold nitrogen gas is the Model 700 series nitrogen gas cryostream cooler supplied by Oxford Cryosystems, 220 Wood Road, Braintree, Mass. 02184. 
     Cryofreezer apparatus  180  includes a shutter mechanism  185  which is attached to transverse outer face  183  of shutter support beam  181 . The shutter mechanism  185  includes a shutter arm  186  that has a straight, rectangular cross section bar member  187  which is pivotally mounted to front face  181 A of shutter support beam  181  by a pivot axle  188  which enables the shutter arm to pivot in a vertical plane. 
     Shutter mechanism  185  also includes a shutter  189  which joins a right-hand portion of shutter arm  186 , and which protrudes to the right of pivot axle  188  and the right-hand side wall  190  of shutter support beam  181 . 
     Shutter  189  includes a laterally disposed, vertical wedge-shaped support plate  191  that has a narrower inner, left-hand end part which is fastened to shutter arm  186 . 
     Shutter  189  also includes a fore-and-aft disposed, generally vertical shield plate  192  located at the inner, right-hand edge of shutter support plate  191 . As shown in  FIG. 25 , shutter arm  186  of shutter mechanism  186  is maintained in a horizontal position by a counterclockwise torque moment exerted around pivot axle  188  by the weight of that portion of the shutter arm located to the left of pivot axle  188 . In this quiescent position, shield plate  192  located at the laterally inwardly located, right-hand end of the shutter arm is positioned in a fore-and-aft, generally vertically disposed position adjacent to the outlet orifice  193  of cryogas supply tube  183 , thus obstructing rightward horizontal flow of cryogas. 
     As shown in  FIGS. 25 and 27 , shutter mechanism  185  includes a curved cam bar  194  which protrudes laterally outwards from the right side of shutter plate  192 , adjacent to its rear edge. Cam bar  194 , which has in front elevation view the shape of a reverse C-shape, has a convex, generally vertically disposed outer right-hand segment  195 . 
     As may be seen best by referring to  FIGS. 5 , and  22 ,  24  and  25 , tool head  73  has protruding radially from a location rearward of longitudinally disposed leg  74  thereof a cylindrically shaped cam follower roller  196  is mounted on the outer radial end of a support bracket  197  which is located behind and parallel to front transverse tool head leg  75 . Cam follower roller  196  is rotatable about a fore-and-aft disposed axle  198  parallel to tool head support arm  63 . Thus, when tool head  73  is positioned adjacent to cam bar  194 , and rotated counterclockwise, cam follower roller  196  pushes leftwards against outer right-hand segment  195  of cam bar  194 . This pushing motion causes shield plate  192  to pivot clockwise, thus allowing unobstructed flow of cryogas from cryogas tube  183  onto a cryoloop  85  held by tool head  73 . 
     As shown in  FIG. 22 , tool head support arm  63  and tool head  73  preferably have a hollow construction including coaxial bores  210 ,  211 , respectively, which are axially aligned. Optionally, bores  210 ,  211  have disposed therethrough a vacuum tube  212  which is connectable at a rear, inner end thereof through a solenoid valve  213  (see  FIGS. 4 and 6 ) to a vacuum source (not shown), and at a front, outer end to a crystal pick-up implement (not shown). 
     FIGS.  1  and  7 - 27  illustrate the manner of using machine  30  to harvest crystals from wells  177  of a crystal growth plate  178 , and cryofreezing the harvested crystals for cryogenic storage and subsequent crystallographic analysis, which is typically performed using an X-ray diffraction instrument. 
     As shown in  FIGS. 24-26 , a first step in using machine  30  to harvest and cryofreeze crystals includes manipulating position control knob  57  of micropositioner apparatus  32  in an upward direction, to thus position tool head  73  in an upper position. The position control knob  57  is then manipulated slightly to the left of center and down slightly until a docking arm  200  which protrudes forward from laterally disposed beam  56 A  60  of micropositioner  32  bumps down against a docking site stationary member  201  which protrudes from vertical micropositioner support plate  72 . As shown in  FIGS. 17 ,  17 A,  19  and  19 A, docking arm  201  is pivotably mounted near a rear end thereof to lateral micropositioner beam  60 . 
     Contact of docking arm  200  with docking site member  201  actuates an electrical switch  202  which provides an input signal to electronic control circuitry  99 . In response to the signal from docking site switch  202 , electronic control circuitry  99  outputs an electrical command signal to tool head angle stepper motor  71 , which causes tool head support shaft  66  to rotate to an angular position in which outer transverse leg  75  of the tool head is oriented in an upright vertical disposition, as shown in  FIG. 9 . In this position, a pickup tool  87  consisting of a cryoloop support cap  79  in which are installed a cryoloop pin  83  and cryoloop  85  is inserted downwards into socket  77  in the horizontally disposed, outer transverse end face  76  of tool head leg  75 . As shown in  FIG. 9 , cryoloop pin  83  is then manually rotated about its longitudinal axis until the plane of the cryoloop is located in a generally fore-and-aft orientation, so that the loop plane is perpendicular to a cryogas stream issuing to the right from cryogas supply tube  183 . 
     After a cryoloop  85  has been installed in tool head  73  and oriented as described above, micropositioner position control knob  57  is manipulated by a human operator to move the tool head support arm and tool head upwards slightly to disengage or “undock” the tool arm from docking site  201 . This action causes electrical switch  202  to provide an open-circuit signal to electronic control circuitry  99 . Then, when the tool arm is moved downwardly a predetermined distance in response to manual operation of the position control knob  57 , downward motion of the follower mechanism causes a flag  204  thereon to interrupt a light beam from a LED of a photo sensor  203  fixed to the machine support structure. In response to a signal from photo sensor  203 , electronic control circuitry  99  outputs an electrical command signal to stepper motor  71  to orbitally rotate crank yoke  101  and attached tool head support arm  63 , clockwise from the vertically upright central docking orientation shown in  FIG. 9 , to a laterally rightward and downward location, at which tool head  73  and cryoloop  85  are angled downwardly and towards the left, i.e., towards the center of the machine. 
     Then, as shown in  FIGS. 1 ,  3 ,  5 , and  23 , position control knob  57  of micropositioner apparatus  32  is manipulated to move tool head  73  down towards work platform  37  and above a selected well of a plurality of wells  176  in the upper surface  177  of crystal growth plate  178  supported on the upper surface of the work platform. In this position, the human operator twists tool angle control knob  92  to pivot tool head  73  to that angular position which orients cryoloop  85  at an optimum inclination angle for harvesting a liquid drop and crystal from a crystal growth well  177 . The operator may then actuate Tool Angle Save switch  101  to store the selected tool angle. 
     With the inclination angle of the cryoloop  85  adjusted as described above, the human operator may then view the cryoloop  85  in relation to a selected crystal growth well  176  through stereo microscope  150 , and manipulate micropositioner position control knob  57  to cause the cryoloop to move obliquely downwards into the well, thus capturing a liquid drop holding a selected crystal within the cryoloop. 
     Position control knob  57  is then manipulated to thus move tool head support arm  63 , tool head  73  and cryoloop  85  holding a liquid drop containing a crystal to an upward position. Upward motion of tool head support arm  63  a predetermined distance causes an electrical signal produced by electrical sensor  203  consisting of a flag  204  and a photo transistor-LED arrangement  205  to command stepper motor  71  to orbit support arm  63  to an upper, leftward location towards the center of the machine. At this orbital position of tool arm  63 , tool head  73  and cryoloop  85  are oriented in an upright, generally vertical crystal retrieval position, as shown in  FIGS. 11 ,  14  and  25 . 
     Position control knob  57  is once again manipulated to thus move tool head support arm a short distance upwards and to the left, and then downwards until perceptible contact is made between docking arm  200  and docking switch  202 , as shown in  FIG. 26 . Actuation of docking switch  202  causes a command signal to be issued to stepper motor  71  to rotate counterclockwise, thereby causing pinion and sector gears to mesh and thus tilt tool head  73  about 2 degrees counterclockwise from an orientation of about one-degree clockwise from a generally vertical orientation shown in  FIG. 25 , to the tilted position shown in  FIGS. 12 ,  15  and  27 . As has been described above, this action causes cryofreezer shield plate  192  to pivot clockwise, thus allowing unobstructed flow of cryogas from cryogas  183  onto cryoloop  85  held in tool head. Tool head  73  is held in this position to allow cryogas to freeze cryoloop  85  and the crystal-containing liquid drop held therein, for a period sufficient to freeze the loop, liquid drop and crystal. This time period is preset by an operator input to Freeze Time Duration digiswitch  89  and ranges typically from about 0.1 second to about 4 seconds or more. 
     Upon expiration of the preset freeze time period, electronic control circuitry  99  outputs a command signal to stepper motor  71  to pivot tool head  73  clockwise to an orientation of about one-degree clockwise from an upright vertical position, as shown in  FIG. 25 , thus causing cryofreezer shield plate  192  to return to a flow-blocking position. Then, as shown in  FIG. 25 , a cryoloop  85  and crystal-containing liquid drop frozen thereto may be removed from tool head  73  and placed in a cryogenic storage container. A new cryoloop  85  may then be inserted into tool head  73 , to enable repetition of a crystal harvesting cycle.