Patent Publication Number: US-2023139694-A1

Title: Preparing substances in a medical diagnostic system

Description:
TECHNICAL FIELD 
     This specification relates generally to techniques for preparing substances for use in a medical diagnostic system. 
     BACKGROUND 
     A medical diagnostic system performs tests on a sample, such as blood or tissue, obtained from a patient. The tests performed by a medical diagnostic system are referred to as assays. An example assay is an investigative procedure for qualitatively assessing or quantitatively measuring the presence, amount, or functional activity of an analyte in the sample. One or more substances, such as reagents, controls, or calibrators, may be used by a medical diagnostic system to perform an assay on a sample. 
     SUMMARY 
     Example techniques may be implemented using a method, a system, or one or more non-transitory machine-readable media storing instructions that are executable by one or more processing devices. Operations performed according to the example techniques include controlling a probe to pierce a stopper of a container containing a substance, where the stopper provides an air-tight seal for the container, and where the air-tight seal supports an internal pressure in the container. The operations also include detecting the internal pressure based on information from a pressure sensor; determining that the internal pressure is not at a target pressure and, based on determining that the internal pressure is not at the target pressure, controlling the probe either to aspirate air from the container or to dispense air into the container in order to move the internal pressure toward the target pressure. The techniques may include one or more of the following features, either alone or in combination. 
     The following operations may be repeated until the internal pressure is within a predefined range of the target pressure: controlling the probe either to aspirate air from the container or to dispense air to the container. Determining that the internal pressure is not at a target pressure may include comparing the internal pressure to information based on the target pressure. The target pressure may be based on ambient pressure and the probe may be controllable to transfer content into the container. The internal pressure may be less than the target pressure prior to transfer of the content into the container. In this case, the probe may be controllable to dispense air into the container prior to transferring the content into the container in order to increase the internal pressure. The internal pressure may be greater than the target pressure following transfer of at least some of the content into the container. In this case, the probe may be controllable to aspirate air from the container after transferring the at least some of the content into the container in order to adjust the decrease the internal pressure. 
     Detecting the internal pressure may include receiving data from the pressure sensor connected to or part of or on the probe. Adjusting the internal pressure toward the target pressure may include maintaining a lower pressure in the container than ambient pressure. The probe may be controllable to dispense air multiple times into the container or to aspirate air from the container multiple times to bring the internal pressure closer to the target pressure. The multiple times may be a predefined number of times. The probe may be controllable based on an expansion of air inside the probe to aspirate additional content from the container. 
     An example probe is configured to aspirate or to dispense a substance. The probe includes a shaft to hold the substance and a hydraulic line that includes hydraulic fluid to create negative or positive pressure in the shaft to aspirate or to dispense the substance, respectively. The probe is controllable to aspirate air prior to aspirating the substance, thereby creating an air gap in the shaft between the hydraulic fluid and the substance. After aspirating the air, the probe is controllable to aspirate substance and air alternately, thereby creating at least one air gap between sections of substance contained in the shaft in addition to the air gap between the hydraulic fluid and the substance. The probe may include one or more of the following features, either alone or in combination. 
     The at least one air gap between sections of substance contained in the shaft may include at least two air gaps. Each of the at least two air gaps may be between two sections of substance, There may be at least between three and five air gaps in the shaft, The shaft may include metal and the hydraulic line may include non-metal resulting in an interface that may allow leakage of the hydraulic fluid into the shaft. The probe may be controllable to dispense substance from the shaft along with air on each side of the substance to be dispensed. 
     Example techniques may be implemented using a method, a system, or more non-transitory machine-readable media storing instructions that are executable by one or more processing devices. Operations performed according to the example techniques include controlling a probe to aspirate air into a shaft of the probe and controlling the probe to dispense air from the shaft into the container to mix at least the first substance and the second substance. The techniques may include one or more of the following features, either alone or in combination. 
     The container may include a vial, the first substance may include a reagent in a liquid or dried/lyophilized form, and the second substance may include a diluent. Dispensing the air from the shaft produces mixture in the vial that is based on the diluent and the reagent and that is at least partially homogenized. Prior to aspirating the air, the probe is controllable to aspirate the second substance into a shaft of the probe, to cause the shaft to enter the container containing the first substance, and to dispense the second substance into the container. The container may hold one or more additional substances in addition to the first substance and the second substance Mixing may include mixing the one or more additional substances with the first substance and the second substance, Either (i) the air is aspirated from inside the container or (ii) the air is aspirated form outside the container and, in (ii), the shaft is controlled to enter the container to dispense the air. The air may be dispensed at a velocity that homogenizes the mixture, 
     Any two or more of the features described in this specification, including in this summary section, can be combined to form implementations not specifically described herein. 
     The systems, techniques, components, structures, and variations thereof described herein, or portions thereof, can be implemented using, or controlled by, a computer program product that includes instructions that are stored on one or more non-transitory machine-readable storage media, and that are executable on one or more processing devices to execute at least some of the operations described herein. The systems, techniques, components, structures, and variations thereof described herein, or portions thereof, can be implemented as an apparatus, method, or electronic system that can include one or more processing devices and memory to store executable instructions to implement various operations. The systems, techniques, components, structures, and variations thereof described herein may be configured, for example, through design, construction, size, shape, arrangement, placement, programming, operation, activation, deactivation, and/or control. 
     The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is block diagram showing components of an example medical diagnostic system on which the example techniques described herein may be implemented. 
         FIG.  2    is a cut-away side view of an example vial and part of a probe. 
         FIG.  3    is a cut away side view of an example robotic probe that is part of the medical diagnostic system. 
         FIG.  4    is a flowchart showing an example method of processing substances using the techniques described herein. 
         FIG.  5    is an example graph showing a build-up of pressure in a container in response to repeated aspirations of air into the container. 
         FIG.  6    is a cut away side view of an example probe shaft containing aspirated air and substance to be dispensed. 
         FIG.  7    is a cut away side view of an example probe shaft containing aspirated air and substance to be dispensed, along with a section of substance and air for absorbing leakage of hydraulic fluid. 
         FIG.  8    is a cut away side view of an example probe shaft containing aspirated air and substance to be dispensed, along with two sections of substance and air for absorbing leakage of hydraulic fluid. 
         FIG.  9    is a perspective diagram showing example vials containing diluent, liquid substance, and lyophilized substance. 
         FIG.  10    is a perspective diagram that illustrates, conceptually, mixing substances in a vial using forced air as a mixing agent. 
         FIG.  11    is a flowchart showing an example process for mixing substances in a vial using forced air as a mixing agent. 
         FIG.  12    is a perspective diagram that illustrates, conceptually, mixing substances in a vial using the aspiration and dispensing of the substances themselves as a mixing agent. 
         FIG.  13    is a flowchart showing an example process for mixing substances in a vial using the aspiration and dispensing of the substances themselves as a mixing agent. 
         FIG.  14    is a flowchart showing an example process for adjusting pressure in a vial or other container that has an initial pressure below a target pressure. 
         FIG.  15    is a flowchart showing an example process for adjusting pressure in a vial or other container that has an initial pressure above a target pressure. 
         FIG.  16    is a flowchart showing an example process for creating sections containing air and substance in a probe shaft. 
     
    
    
     Like reference numerals in different figures indicate like elements. 
     DETAILED DESCRIPTION 
     Described herein are examples of medical diagnostic instruments, systems, and variants thereof (referred to collectively as “the system”) that implement techniques for preparing substances for use in an assay. In this regard, the system may include test containers called vials. The vials may include any substance needed to implement an assay. Examples of substances that may be included in the vial include, but are not limited to, diluent and reagents. Examples of diluents that may be used include but are not limited to deionized (DI) water, buffers, and liquid mixture of different chemicals. Examples of reagents that may be used include, but are not limited to, simple and/or complex chemical mixtures. 
     When an assay needs to be prepared prior to running tests on the system, the substances in the assay are prepared inside the vials contained in a cartridge. In an example, a first one of the vials may contain a lyophilized substance or a liquid substance and a second one of the vials may contain diluent, such as DI water. To prepare the substances for use in an assay, a probe in the system may move diluent from the first vial into the second vial to mix the diluent and the substance. Example preparations include rehydrating a freeze-dried component (substance) or mixing together multiple components (substances) prior to use. Generally, substances in dry (e.g., lyophilized) form are stored in vials well below ambient pressure, for example, at or near vacuum. Substances in liquid form may be stored in the vials with a slightly positive internal pressure. 
     The pressure differential between the interior and exterior of a vial can cause problems during extraction of substance from a vial or dispensing in a vial. For example, if the pressure inside the second vial is well below ambient pressure—that is, considerably negative—this can result in suctioning unwanted substances into the vial from a probe (or needle) when a stopper of the vial is pierced. For example, if the pressure inside the vial is above ambient pressure—that is positive—this can result in substances erupting or leaking from the vial when its stopper is pierced. 
     Generally, prior to the vial&#39;s use, the system performs a pressure equilibration for the vial such that the vial&#39;s internal pressure can reach a target pressure, In some implementations, the pressure equilibration can be performed using a probe that is the same as the probe for aspiring substances from the vial or a different device, such as probe designated to perform the equilibration. A benefit of using the same probe may be a potential reduction in contamination, whereas a benefit of using a different device is that there may be additional flexibility in system design. The pressure equilibration can be implemented by aspirating air from the vial or dispensing air into the vial to adjust the internal pressure of the vial toward a target pressure. 
     In an example implementation, a probe is controlled to pierce a stopper of the vial, which provides an air-tight seal maintaining the internal, non-ambient pressure within the vial. A pressure sensor is connected to or part of or on the probe. The internal pressure of the vial is detected based on information from the pressure sensor connected to or part of or on the probe. The system determines that the internal pressure is not the target pressure or within an acceptable range thereof. Then, prior to moving any substance into or from the vial, the probe is controlled to aspirate air from the vial if the pressure is positive or to dispense air into the vial if the pressure is negative relative to the target pressure in order to move the internal pressure toward the target pressure. 
     Penetrating the vial to aspirate air from the vial or to dispense air into the vial may be performed multiple times—for example, a predefined number of times—prior to moving any substance into or from the vial and/or between transfers of substance into or from the vial in order to reach and/or to maintain a pressure in the vial at or near a target pressure. Other techniques for adjusting pressure are also described herein. 
     As noted, the probe used for pressure equilibration, referred to as an equilibration probe, can be the same as, or different from a probe that transports substances to or from the vials, referred to as a transport probe. In some implementations, any one or all of the probes described herein are hydraulic. For example, the transport probe may include a hydraulic line that holds hydraulic fluid, such as DI water. Flow of the hydraulic fluid is controllable to create a negative pressure or a positive pressure in its shaft in order, respectively, to aspirate a substance into the shaft or to dispense a substance from the shaft. The interface between the hydraulics and the remainder of the probe, including the shaft, may produce a hydraulic fluid to leak into the shaft. The leaked hydraulic fluid may contaminate a substance that has been aspirated into the shaft, For example, a substance aspirated into the shaft for movement from one vial into another vial (or another container, such as a cuvette) may be contaminated by the leaking hydraulic fluid. In this context, contamination may include diluting the substance with the hydraulic fluid. 
     To reduce such contamination and the deleterious effects thereof, the probe is controlled to create an air gap between the hydraulic fluid and the substance in the shaft and to create multiple sections of substance-air gaps in the shaft, with each layer of substance being separated from an adjacent layer of substance by an air gap. In the event of a hydraulic fluid leak, the multiple sections of substance and air reduce the amount of hydraulic fluid that reaches substances aspirated into the probe. 
     In some examples, a probe may contain a shaft having a lumen, such as a needle. To mix substances in the vial or cuvette, a probe, referred to as a mixing probe, may be controlled to aspirate air into its shaft. The mixing probe may be the same probe as the equilibration probe and/or the transport probe, or the mixing probe may be a different device. Advantages of using the same probe for equilibration, transport, and mixing may include, but are not limited to, efficiency and cost effectiveness without compromising performance and/or increasing contamination/carry over. 
     The mixing probe may be controlled so that its shaft pierces the vial&#39;s stopper and dispenses air from the shaft into the vial to mix the substances in the vial. The air may be forced into the vial at such velocity to promote or to ensure sufficient homogenization of the substances, or aspirate and dispense the liquid mixture enough times to ensure sufficient homogenization of the substances, e.g., in such way that the resulting analytical performance of the homogenized substances is equivalent to the standard assay, experimentally assessed based, for example, on previous experimentation. Other techniques for mixing the substances also described herein. 
     The devices for use in performing equilibration, transporting, and mixing may be devices other than probes, such as but not limited to robotic arms, so long as the devices perform the appropriate functions, such as mixing/homogenizing in such way that the analytical performance of the resulting homogenized substances is equivalent to the standard assay, as experimentally assessed. In the description below, any type of other device may be substituted for the probe. 
       FIG.  1    shows a block diagram of an example system  10  configured to implement the techniques described in the preceding paragraphs. The techniques described herein, however, are not limited to use a system such as that shown in  FIG.  1   . The system of  FIG.  1    is provided as an example for illustration only. 
     System  10  includes a medical diagnostic instrument  11  for receiving and for holding test cartridges (“cartridges”)  12 . Each cartridge holds containers, such as the vials that contain the substances that are used in the assays described herein. The substances in the vials and/or the vials in the cartridges may be processed for use with a particular assay. Processing may include, but is not limited to, changing or equilibrating the internal pressure of vials in the system, transporting substances to and from the vials, and/or mixing substances at the transported location, e.g., in a vial or in a cuvette or another testing related container/chamber, prior to use in an assay. The processing may be performed using one or more controllable robotic probes (“probe”) such as probe  30  in  FIG.  2    or probe  44  of  FIGS.  3  and  9   . For example, the probe is controllable to move between and into the vials in order to implement all or some of the techniques described herein, The probe may be hydraulic, as described herein and, when transporting substances, may be controlled to create an air gap between the probe&#39;s hydraulic fluid and the substance in the probe&#39;s shaft and to create multiple layers of substance in the shaft, with each substance layer being separated from an adjacent substance layer by an air gap. Among other functions, as described below, the probe may also be used to mix/homogenize the substances in the vials by air injection (as in  FIGS.  10  and  11   ) and/or by aspirating and dispensing the liquid substances in the vial (as in  FIGS.  12  and  13   ). The mixing process starts when all necessary substances are in a container, as described in more detail below. 
     Control over system  10  may be implemented by a control system  20  embedded in, and/or associated with, instrument  11 . In some implementations, components of the control system may be distributed across instrument  11  and/or one or more computing devices  21  in communication with instrument  11 . The control system may be or include one or more processing devices  22 , examples of which are described herein. The processing devices  22  may reside within instrument  11  or be external to instrument  11 —for example externally local to, or remote from, instrument  11 . In some implementations, processing devices  22  may reside within computing system  21 . Computing system  21  may be separate from instrument  11  but may be connected to instrument  11  directly or via a wired or wireless computer network to enable communication between instrument  11  and computing system  21 . In some implementations, control system  20  includes a controller printed circuit board (PCB)  23  having one or more of the processing devices  22  that are programmable to control operations of various system components. Controller PCB  23  may be embedded in instrument  11  or external to instrument  11 . Control system  20  may also include machine-readable and writable memory  24 , which may be internal and/or external to instrument  11 , and which stores data and computer programs that are executable by one or more processing devices on the controller PCB and/or the computing system. The instrument has the ability to identify any of the contents that are loaded into the instrument and will execute equilibration, transport, and/or mixing instructions based on the substances included in the vials loaded into the instrument. 
     Referring to  FIG.  2   , the cover of example vial  32 , referred to as a stopper above, creates an air-tight/fluid-tight seal with the vial. Within the vial, the unequilibrated pressure may be positive or negative relative to ambient pressure, as described herein. The stopper may be made of plastic, rubber, or other elastic material that can be pierced by the probe.  FIG.  2    shows a probe shaft  29  piercing a stopper  31  of vial  32 . 
     In this case, the stopper includes a top part  31   a  and side parts  32   a  that conform to the inner walls of the vial and that create the air-tight I fluid-tight seal between the stopper and the vial. As shown in  FIG.  2   , shaft  29  pierces and penetrates stopper  31  until shaft  29  extends into the interior volume  34  of the vial. Shaft  29  may continue into the interior until it reaches the bottom  35  of the vial. After the probe&#39;s shaft is retracted from the vial and the stopper, the material that forms the stopper caves-in on the hole created by the shaft, thereby reforming the air-tight/fluid-tight seal between the stopper and the vial. In other words, the stopper self-seals after the probe&#39;s shaft is retracted, thereby reforming the air-tight/fluid-tight seal. When the stopper self-seals, any equilibration previously performed can be maintained 
     An example of a robotic probe  44  that may be used in system  10  is shown in  FIG.  3   . In this example, probe  44  is robotic in the sense that it is machine-controllable to move, to aspirate, to dispense, and to perform other operations absent manual manipulation. In some implementations, the robotic probe may be user-controllable in the sense that the control system may receive user inputs as to how the probe is to operate, e.g., what tests to perform. But, after those user inputs are received, the robotic probe may be controlled automatically by the control system—for example, the robotic probe may be controlled to equilibrate pressure, to transport a substance, and/or to mix substances in the manners described herein. 
     Probe  44  includes a housing  45  and a shaft  46  having a lumen  47 . Shaft  29  of  FIG.  2    may have the same configuration as shaft  47 . An example shaft and lumen structure includes a needle. As shown in  FIG.  3   , shaft  46  has a tip  48  that is pointed to pierce through the stopper  31  of a vial  32  ( FIG.  2   ) and to enter the interior of the vial. Liquid substances are aspirated from, or dispensed into, a vial through lumen  47  in shaft  46 . A pressure sensor  50  is connected to or part of or on the probe. Pressure sensor  50  may be a wired or wireless pressure sensor in that its readings may be transmitted to the control system over a wired connection or over a wireless connection. Pressure sensor  50  is configured to detect the pressure inside a vial after the stopper has been pierced by the probe&#39;s shaft. Information representing the pressure inside the vial is sent to the control system, which may then control the probe to change—for example, to increase or to decrease—the pressure in the interior of the vial as described herein. 
     Referring to  FIG.  4   , the probe may be used for pressure equilibration ( 26 ) or pressure correction on a container such as a vial. Following pressure equilibration correction, the same probe or a different transport probe may transport ( 27 ) substance from a different container to the container or vial that has been subjected to pressure equilibration or correction. And, following substance transport, the same probe or a different mixing probe may mix ( 28 ) the substance that was transported with another substance in the container or vial as described herein. 
     Pressure equilibration includes aspirating and/or dispensing air as part of a transfer to keep control of vial pressure. Pressure equalization may be implemented in at least two instances: before a sealed vial is used (e.g., to change internal pressure set at manufacturing) or during the use of the vial. Some air transfers, particularly those that are larger such as 10 mL or greater, may be implemented by actively controlling operation of the probe. The techniques described below include actively adding air to a vial or removing air from a vial. In some implementations, the air moved to or from a vial is controlled to keep the vial at a slight vacuum—that is, at a slightly negative pressure relative to ambient pressure such as those described above. This slightly negative pressure may prevent liquid from escaping from the vial when the probe is removed from the vial through the hole in the seal or stopper created by the probe. In some implementations, the target pressure may be 1% less than ambient pressure, 2% less than ambient pressure, 3% less than ambient pressure, 4% less than ambient pressure. 5% less than ambient pressure, 6% less than ambient pressure, 7% less than ambient pressure, 8% less than ambient pressure, or 9% less than ambient pressure, In an example, ambient pressure is standard atmospheric pressure, which is defined in various units as 760 millimeters (mm) (29.92 inches) of mercury, 14.70 pounds-per-square-inch, 1,013.25×103 dynes-per-square-centimeter, 1,013.25 millibars, or 101.325 kilopascals pressure at sea level. Notably, however, target pressures other than the examples presented herein may be achieved using the system, the probe, and the techniques described herein. 
     The target pressure for inside the vial may be set by the control system based on the type of assay to be performed, the preparation process associated with the assay, the substance in the vial, and/or the substances used in the assay, for example. 
     Equilibrating the pressure to close to ambient pressure may reduce the chances that substances be inadvertently drawn into the vial or expelled from the vial due to the internal pressure of the vial. If the internal pressure is much higher than the ambient pressure, when a substance is added the internal pressure will increase, and when the probe is removed, some of the substance may come out with the probe to the outside of the stopper because the higher internal pressure pushes it out. If the internal pressure of the vial is much lower than the ambient pressure then, when some substance is dispensed into the vial, the lower pressure (vacuum) may pull more substance from the probe than what is required, including bringing some hydraulic fluid into the vial and making the dispensing more difficult to control. 
     In an example pressure equilibration process  115  ( FIG.  14   ), the probe&#39;s shaft  46  ( FIGS.  10  and  12   ) enters ( 115   a ) the interior volume of vial  32 . This creates a fluidic pathway along the shaft&#39;s lumen between the interior of the vial and pressure sensor  50  ( FIG.  3   ). Pressure sensor  50  connected to or part of or on shaft  46  detects ( 115   b ) the internal pressure of the vial. The pressure sensor sends data representing the internal pressure to the control system. The control system compares the detected pressure to a target pressure, such as a pressure that is slightly less than ambient pressure, in order to determine if the detected pressure deviates from the target pressure by more than an acceptable amount. For example, an unacceptable deviation may include a 2% deviation, a 5% deviation, or more. The target pressure for each vial may be stored in memory in the control system. The control system may control operation of the probe to adjust the internal pressure of the vial based on this target pressure. 
     The control system determines ( 115   c ) that the internal pressure of the vial deviates from the target pressure by an unacceptable amount. Accordingly, the control system controls probe  44  ( FIG.  3   ) to adjust the internal pressure of the vial toward the target pressure. As previously noted, the target pressure may be a negative pressure or a positive pressure that is different from the initially-detected internal pressure of the vial. In this regard, assuming that the target pressure is slightly less than ambient pressure and that the internal pressure is a negative pressure and below the target pressure, the control system controls the probe to aspirate ( 115   e .  FIG.  14   ) air from the outside of the vial into its shaft, to move to the location of the vial, to pierce the vial&#39;s stopper with the probe shaft, and to dispense ( 115   f )—that is, to inject—the aspirated air into the vial, thereby increasing the air pressure within the vial. The amount of air that is aspirated may be a predefined amount that is programmed into the control system. The pressure sensor  50  connected to or on or part of the probe then reads the new pressure in the vial—that is, the pressure that resulted after the air was added to the vial. The pressure sensor then sends data representing the new pressure to the control system. 
     The system may then repeat operations  115   b  to  115   f  ( FIG.  14   ) until the target pressure is reached inside the vial, or until a pressure within an acceptable range of the target pressure is reached inside the vial. In this regard, in some implementations, examples of an acceptable range may include a 1% deviation from the target pressure, a 2% deviation from the target pressure, a 3% deviation from the target pressure, a 4% deviation from the target pressure, a 5% deviation from the target pressure, a 10% deviation from the target pressure, and so forth. 
     For vials that have not previously been used, e.g., manufactured and known to be at a predefined pressure that is close to vacuum, air may be repeatedly injected from the probe into the vial without the probe having to leave the vial. For example, after the first injection of external air into the vial by the probe, the probe may aspirate air from the vial and inject the aspirated air back into the vial multiple times without leaving the vial. This repetition may cause equilibration of the air pressure in the vial to the ambient pressure. 
     In some examples, the probe may be pre-programmed to aspirate and inject air into the vial a predefined number of times that is independent of measurements by the pressure sensor. In an example situation, the control system identifies a previously unused vial from a source that is known to be at near vacuum. Air is injected a predefined number of times, for example, 4 to 7 times, to reach equilibration. In other examples, the probe may aspirate and inject air into the vial 20 times; however, other numbers of times may be used, such 10 times, 30 times, 40 times, and so forth. 
       FIG.  5    shows pressure  120  in pounds per square inch, gauge (psig). In this regard, a container that initially is vacuum sealed—for example, does not hold any air (e.g., at near vacuum internal pressure), would be approximately −14.7 PSIG. 0 PSIG is used as a surrounding/ambient air pressure. In this example, the pressure  121  within a vial starts out at level  122  that is close to vacuum pressure. Air is aspirated into the vial 20 times in this example, with each peak  123  representing an aspiration of air. Each individual amount of air that is injected may be less than that required to reach equilibrium, with equilibrium reached after multiple injections. The end pressure  124  in the vial is at or slightly below the surrounding air pressure, as shown in the figure. 
     Referring to  FIG.  14   , for vials not known to be at vacuum pressure, operations  115   c  to  115   f  may be repeated based on readings from pressure sensor  50  as described above. Each time after air is added to the vial, pressure sensor  50  connected to or part of or on the probe reads the new pressure in the vial—that is, the pressure that resulted after the air was added to the vial. The pressure sensor then sends data representing the new pressure to the control system. These operations may be repeated multiple times in order to achieve the target pressure within the vial. If the pressure unacceptably exceeds the target pressure as a result of the addition of too much air to the vial, an amount of air may be removed from the vial to keep the pressure inside the vial at the target pressure, e.g., ambient pressure, as described below. 
     In this regard, example process  115  of  FIG.  14    illustrates a case where the internal pressure of the vial is negative. Example process  117  of  FIG.  15    includes operations that are performed by the system when the internal pressure in a vial is positive relative to the target pressure. The operations may be performed on a vial hat has not previously been used or on a vial to which too much air has been added to cause the internal pressure to exceed the target pressure. More specifically, in the case of a target vial such as vial  32  ( FIG.  2   ), the probe&#39;s shaft  46  ( FIG.  46   ) first enters ( 117   a ) the interior volume of that vial. Pressure sensor  50  connected to or on or part of shaft  46  detects ( 117   b ) the internal pressure of the vial in the manner described above with respect to process  115 . The pressure sensor sends data representing the internal pressure to the control system. 
     The control system compares the detected pressure to a target pressure, such as a pressure that is slightly less than ambient pressure, in order to determine if the detected pressure deviates from the target pressure by more than an acceptable amount. The control system determines ( 117   c ) that the internal pressure of the vial deviates from the target pressure. Accordingly, the control system controls the probe to adjust the internal pressure of the vial toward the target pressure. In this example, the internal pressure is a positive pressure, and the target pressure is slightly less than ambient pressure. Accordingly, the probe vial aspirates ( 117   e ) a predefined amount of air from the vial, thereby decreasing the air pressure within the vial. The predefined amount may be programmed into the control system based on the substance in the vial and the assay to be performed using the vial. The pressure sensor  50  then reads ( 117   f ) the new pressure in the vial—that is, the pressure that resulted after the air aspirated from the vial into the probe. The pressure sensor  50  then sends data representing the new pressure to the control system. The probe also exits the vial and dispenses ( 117   g ) the air that was aspirated from the vial in a region outside of the vial. 
     The control system may then repeat process  117  or portions thereof until the target pressure is reached inside the vial, or a pressure within an acceptable range of the target pressure is reached inside the vial. Regarding repeating the process, the control system determines whether the new internal pressure of the vial deviates ( 117   c ) from the target pressure. If so, then the control system controls the probe to adjust the new internal pressure of the vial further toward the target pressure. 
     As noted, assuming that the internal pressure is positive pressure and the target pressure is slightly less than ambient pressure, the control system controls the probe to retract from the vial completely, to dispense air from the probe that has aspirated from the vial, to pierce the vial&#39;s stopper again with the shaft, and to aspirate additional air from the vial. The pressure sensor  50  connected to or on or part of the probe then reads the new pressure in the vial—that is, the pressure that resulted after the additional air was aspirated the vial. The pressure sensor sends data representing the new pressure to the control system. These operations may be repeated multiple times to reach target pressure within the vial. If the pressure goes unacceptably below the target pressure, which may be caused by removing too much air from the vial, an amount of air to keep the pressure inside the vial at the target pressure may be added to the vial as described above, 
     In some implementations, following initial pressure measurement, the control system may determine the number of aspirations from the vial that are needed to obtain the target pressure. For example, the control system may know the volume that the probe can aspirate, and the amount of air needed to aspirate for the vial to reach the target pressure. The control system may then control the probe to make a number of aspirations from the vial to keep the pressure inside the vial at the target pressure 
     Some air transfers may self-equalize due to minor air exchange as the probe enters or leaves a vial. In an example implementation, air may be aspirated into the probe before entering the vial. When the probe penetrates the vial, a pressure differential between the probe and the interior of the vial causes air to go into or out of the vial and thereby self-equalize the internal pressure. For example, if the pressure in the vial is greater than the pressure in the probe, air may transfer from the vial to the probe, thereby decreasing the pressure in the vial. In another example, if the pressure in the vial is less than the pressure in the probe, air may transfer from the probe to the vial, thereby increasing the pressure in the vial. This may be implemented without actively injecting or removing the air. Techniques such as these are referred to as passive pressure control techniques since they do not require hydraulic operation of the probe while the probe is in the vial in order to implement an air transfer. These techniques may be used, for example, if too much air is added to, or removed, from a vial and small additional changes in pressure needed. Passive techniques, however, are not limited to use in this context. 
     The foregoing operations may be performed to reach a pressure equilibrium between the internal pressure of the vial and the target pressure. After the target pressure is reached or within an acceptable range, the probe may retrieve substances and transport the retrieved substances to the vial for addition to the vial. 
     In some implementations, such as those described below, adding substance to a vial may also include adding air to the vial. Additionally, air may be extracted from the vial or leak from the vial. This may change the air pressure in the vial—for example, increase the air pressure within the vial to an unacceptable level. Accordingly, the techniques described herein may be used to adjust the pressure within the vial during substance transfer—for example, in between two consecutive substances transfers. By way of example, when a substance is dispensed into the vial, the pressure sensor connected to or part of or on the probe shaft sends data to the control system representing the pressure in the interior of the vial. The control system determines whether the internal pressure of the vial deviates from the target pressure by an unacceptable amount. If so, then the control system controls the probe to adjust the internal pressure of the vial toward the target pressure. In an example, the internal pressure exceeds the target pressure by an unacceptable amount. Accordingly, the control system controls the probe to move to a location in the vial that does not include substance to be mixed, and to aspirate air from the vial, thereby decreasing the air pressure within the vial. The amount of air that is aspirated may be based on the pressure change that is desired, The pressure sensor  50  connected to or part of or on the probe then reads the new pressure in the vial—that is, the pressure that resulted after the air aspirated from the vial into the probe, The pressure sensor then sends data representing the new pressure to the control system, The control system may then repeat the operations described above until the target pressure is reached inside the vial, or a pressure within an acceptable range (e.g., 1%, 2%, etc. deviation) of the target pressure is reached inside the vial. If the pressure goes unacceptably below the target pressure, an amount of air may be added to the vial to keep the pressure inside the vial at the target pressure as described above. For example, as described above, the control system controls the probe retract from the vial, to aspirate air into its shaft, to pierce the vial&#39;s stopper again, and to dispense—that is, to inject—the aspirated air into the vial. The pressure sensor  50  connected to or on or part of the probe then reads the new pressure in the vial—that is, the pressure that resulted after the air was added to the vial. The pressure sensor then sends data representing the new pressure to the control system, which may further adjust the pressure, if necessary. Thus, pressure control and/or equilibration may be performed between transfer of substances into a vial and/or during transfer of substances into a vial, as described above, 
     When aspirating substances such as liquid substance, e.g., a reagent, from a vial, the pressure in the vial decreases, One effect of this pressure change is an expansion of any air gaps in the probe—for example in its shaft as described with respect to  FIGS.  7  and  8    below. When these air gaps expand, the air gaps reduce the total volume of substance that can be drawn into the probe. To address this, particularly in the case of aspirating liquid, the control system may keep track of the volume of substance aspirated into the probe and predict the expansion of the air gaps in the probe using gas expansion calculations, such as the ideal gas law. The volume of substance of the probe may be tracked by keeping a record of the volumes of substance, including substance and air, that has been aspirated into the probe. Based on the predicted expansion of the air, the control system may perform a correction to account for the predicted expansion of the air. For example, after the probe has been emptied of a dispensed substance, the control system may control the probe to aspirate additional substance, such as liquid reagent, from the vial in order ensure that the proper amount of substance has been transferred and the pressure in the vial is maintained at the target pressure. Pressure equilibration may be performed after substance transfer, if necessary. 
     Referring back to  FIG.  3   , in an example. probe  44  includes a hydraulic connection, which may be or include a tube  51 —also referred to as a “line”—that holds hydraulic fluid. An example of hydraulic fluid is DI water; however, other types of fluid, such as ACL TOP Rinse solution may be used as the hydraulic fluid. Tube  51  is in fluid communication with lumen  47  of shaft  46 . This fluid connection enables air to flow between the shaft and the tube; that is, from the tube into the shaft and from the shaft into the tube. The latter flow can occur when air or substances are aspirated into the probe and the former flow occurs when the air or substances are dispensed from the probe. That is, air flow from the shaft into the tube produces suction that enables aspirating. Air flow from the tube into the shaft produces pressurized air in the shaft that enables dispensing. Thus, the hydraulic fluid may be controlled by the control system to flow in a direction toward the shaft to cause positive pressure in the probe&#39;s shaft to dispense air or substance therefrom. The hydraulic fluid may be controlled by the control system to flow in a direction away from the probe&#39;s shaft to cause negative pressure in the probe&#39;s shaft to aspirate air or substance into the probe&#39;s shaft. 
     In some implementations, housing  45  and shaft  46  are made of metal, such as a stainless-steel alloy or any material that yields similar or better performance than stainless-steel alloy, and tube  51  is made of plastic, rubber, or any other pliable material that yields similar or better performance than plastic or rubber. Due to the differences in pliability between the tube and the housing/shaft part of the probe, the interface between the tube and the housing/shaft part of the probe may not be air-tight/fluid-tight, As a result of this imperfect seal at the interface, hydraulic fluid may leak from tube  51  into shaft  46 , thereby contaminating (e.g., diluting) the substance aspirated into the shaft, as described previously. To address this potential contamination, the probe is controllable by the control system to create multiple sections—for example air and liquid substance sections—between the hydraulic fluid and the substance to be dispensed by the probe. For example, the probe is controllable by the control system to create an air gap between the hydraulic fluid and a substance in the shaft and to create multiple downstream layers of substance in the shaft, with each layer of substance being separated from an adjacent layer of substance by an air gap. As described below, there may be between three and five sections of air and substance, or more if needed. However, the system is not limited to any specific number of pairs of air and substance. 
       FIG.  6    shows the result of a technique in which the control system controls the probe to aspirate air  61  into shaft  62  and then to aspirate, into the shaft, a substance  64  to be dispensed. Air  61  aspirated before substance  64  produces an air gap between substance  64  and hydraulic fluid  65  (DI water) in tube  67 . This air gap creates pressure in the shaft that may reduce leakage of hydraulic fluid into substance  64 . The control system also controls the probe to aspirate air  69  into the shaft  62  after aspirating substance  64 . This creates a second air gap that may reduce the chances that substance  64  inadvertently leaks from the probe. Although there may be reductions in leakage, the configuration of  FIG.  6    may produce enough hydraulic fluid leakage to significantly contaminate substance  64  to be dispensed. Accordingly, additional section(s) are added as shown in  FIGS.  7  and  8    to address this issue. 
       FIG.  7    shows the result of an example technique in which the control system controls the probe to aspirate a section  71  including substance and air that is upstream of substance  72  to be dispensed from shaft  73 . In this example, substance  72  to be dispensed by the probe corresponds to substance  64  from  FIG.  6   . In some examples, the transfer volume of the substance is always the same for a specific transfer no matter how many sections are used. That is, in some examples, the volume of substance in the sections does not change the volume of the substance to be transferred, which is a volume needed for the preparation. 
     The air gaps in  FIG.  7   , however, may have the same or smaller volumes as the air gaps of  FIG.  6   . In the example of  FIG.  7   , before aspirating substance  72  to be dispensed, the control system controls the probe to aspirate a first volume of air  76  outside of a vial to produce an air gap, then to aspirate a first volume of substance  77  from inside of a vial, then to aspirate a second volume of air  78  outside of a vial. The resulting section  71  of air  76  and substance  77  separates substance  72  to be dispensed from hydraulic fluid  79  (e.g., DI water) in tube  80 . As described previously, air pressure provided by air  76  may reduce leakage of hydraulic fluid  79 . However, if hydraulic fluid leaks into the shaft, all or some of that hydraulic fluid may be absorbed by substance  77  in section  71 . As a result, no hydraulic fluid, or a lesser amount of hydraulic fluid, will reach substance  72  to be dispensed than in the configuration of  FIG.  6   . As described previously, pressure produced by air  78  may reduce the likelihood and/or amount of fluid leaks into substance  72 . As a result, substance  72  will not be contaminated by, or will have less contamination, than if section  71  were not present in the shaft. The control system also controls the probe to aspirate air  72   a  into the shaft after aspirating substance  72 . This creates and air gap that may reduce the chances that substance  72  inadvertently leaks from the probe. 
       FIG.  8    shows the result of an example technique that extends the example described with respect to  FIG.  7   . More specifically,  FIG.  8    shows the result of an example technique in which the control system controls the probe to aspirate two sections  56  and  57 , each comprised of substance and air, that are upstream of substance  53  to be dispensed by the probe. In this example, substance and air  82  to be dispensed by the probe corresponds to substance and air  74  from  FIG.  7   . The air gaps may have the same volumes as the counterpart air gaps of  FIG.  7    or may have lesser volumes. In this example, before aspirating substance  53  to be dispensed, the control system controls the probe to aspirate a first volume of air  83  from outside a vial to produce an air gap, then to aspirate a first volume of substance  84  from inside a vial. The control system then controls the probe to aspirate a second volume of air  86  from outside a vial to produce an air gap, then to aspirate a second volume of substance  88  from inside a vial. The control system then controls the probe to aspirate a third volume of air  89  from outside a vial. 
     The two sections  56  and  57  separate substance  53  to be dispensed from hydraulic fluid  90  (DI water) in tube  91 . As described previously, air pressure provided by each air gap may reduce leakage of hydraulic fluid through and beyond that air gap, However, if the hydraulic fluid leaks into the shaft, all or some of that hydraulic fluid may be absorbed by substance  84  and substance  88 . As a result, no hydraulic fluid, or less hydraulic fluid, will reach the substance  53  to be dispensed. More specifically, hydraulic fluid that leaks through air  83  will be absorbed by substance  84 . Hydraulic fluid that leaks through both substance  84  and air  86  will be absorbed by substance  88 . As described previously, pressure produced by air  89  may reduce likelihood and/or among of fluid leaks into substance  53 . As a result, substance  53  will not be contaminated by, or will have less contamination, than if sections  56  and  57  were not present in the shaft. 
     In the implementations of  FIGS.  7  and  8   , for example, by using layers of substance separated by air gaps or sections of substance-air gap, the probe can reduce the amount of hydraulic fluid in the substance that is dispensed to the vial to make it insignificant. That is, while some hydraulic fluid may leak into layers of substance nearer to the interface even in the presence of air gaps, by separating the hydraulics from the remainder of the probe, most or all the hydraulic fluid will be absorbed by layers of substance closest to the interface before the hydraulic fluid reaches the layer or layers of substance to be dispensed into the vial (or cuvette). 
     In some implementations, there may be more than two sections  56  and  57  of air and substance in the shaft upstream of substance  53  to be dispensed. For example, there may be three sections of air and substance (three sections) in the shaft upstream of the substance be dispensed. For example, there may be four sections of air and substance (four sections) in the shaft upstream of the substance be dispensed. For example, there may be five sections of air and substance (five sections) in the shaft upstream of the substance be dispensed. For example, there may be six sections of air and substance (six sections) in the shaft upstream of the substance be dispensed. The number of sections to create may be predefined by the control system and may be based, for example, on the assay to be performed. In some example, the greater the number of sections upstream of the substance to be dispensed, the less likely that the content to be dispensed will become contaminated with hydraulic fluid. 
     Referring to the example process of  FIG.  16    and the example of  FIG.  7   , to create section  71 , the control system controls the probe to aspirate ( 125 ) air  76  from outside of a vial containing a substance to be dispensed. The control system may control the probe to enter ( 126 ) the vial containing substance and to aspirate ( 127 ) that substance from the vial. The control system may control the probe to aspirate ( 128 ) air  78  either from inside the vial or outside the vial based, for example, on pressure considerations within the vial as described herein. For example, if the pressure in the vial exceeds a target pressure, air  78  may be aspirated from within the vial. If the pressure in the vial is at the target pressure, the probe may be removed from the vial and air  78  may be aspirated from external to the vial. The probe may again enter the vial to aspirate ( 129 ) substance  72 . Thereafter, the air  72   a  may be aspirated ( 130 ) from within or outside of the vial, as was the case above. The amounts to aspirate may be controlled by the control system based, for example, on predefined parameters or the assay being performed. These operations may be repeated as necessary based on the number of sections to be formed within the probe, which may be based on factors such as the assay to be performed or the substances being used in the assay. 
     The positive pressure in the probe is determined and controlled to dispense the layer or layers of substance (e.g., substance  72  or  53 ) in the shaft that are farthest from the interface between the hydraulics and the remainder of the probe. Those layers may contain no, reduced, or minimal contamination, from the hydraulic fluid. The control system may determine the positive pressure to apply to the probe based, for example, on predefined parameters stored in memory, the assay being performed, the substance being aspirated, and any other information needed for the accurate and effective pressure adjustment and equilibration. In some implementations, the amount of substance to be dispensed may be based on the size of the shaft and the number of sections of air and substance that precede the substance to be dispensed. In some implementations, the volume of substance to be dispensed that may be aspirated is on order of fives or tens of microliters—for example, 5 μL, 10 μL, 15 μL, 20 μL, 25 μL, 30 μL, 35 μL, 40 μL, 45 μL, 50 μL, and so forth. This amount may be more than the amount of substance used in the sections. In the example implementations of  FIGS.  7  and  8   , the shaft can aspirate a total of 1,100 microliters ( μL) of content including air gaps, substance, and sections; however, in other implementations, different amounts of content may be aspirated depending, in part, on the size of the probe. 
     In some implementations, each air gap is on order microliters (μL) of air—for example, 1 μL, 5 μL, 10 μL, 15 μL, 20 μL, 25 μL, 30 μL, 35 μL, 40 μL, 45 μL, 50 μL, and so forth. Air gaps having volumes other than these may also be used. In some implementations, the substance in each section may be 10 μL, 20 μL or other amounts such as 5 μL, 15 μL, 25 μL, 30 μL, 35 μL, 40 μL, 45 μL, 50 μL, and so forth. In some examples, each section has the same volume of substance not matter how many sections are used. In some implementations, the more sections that are used, the smaller the amount of substance in each volume there is. 
     The substance included in the sections, such as sections  56  and  57 , is the same substance that is to be dispensed by the probe. The control system calibrates positive pressure in the shaft based on the size and/or number of sections to ensure that the sections are not dispensed with substance or to reduce the chances that the sections will be dispensed with substance. For calibration, the pressure is measured by the pressure sensor and is equilibrated based of the difference relative to the ambient pressure. The volume to be dispensed is dictated by the command in the preparation software that establishes how much volume (in μL) is to be dispensed. This information has been obtained based on previous experimentation. 
     In some examples, the same probe that is used to aspirate substances from vials and to dispense substances into vials (e.g., to transport substances) may also be used to mix two or more substances. For example, two or more substances may be mixed within a container, e.g., a vial or a cuvette, in which the substances were dispensed or in another container prior to being transferred into a vial. Mixing of two or more substances may be performed to perform an assay. For example, vials each may hold a substance that is usable to perform an assay on a sample. However, to perform the assay, two or more of the substances may need to be mixed beforehand in some implementations, this mixing may need to be of sufficient duration and to be done with sufficient force to create a mixture of the two substances that is fully or at least partially homogenized (e.g., the mixing may be performed in such way that the analytical performance of these homogenized substances is equivalent to the standard assay, as experimentally assessed). Homogenization includes combining the two substances so that they are each distributed uniformly or consistently in the resulting mixture. 
     In an example, the mixture may be in a vial and may be based on—for example, formed from—a diluent (e.g., a liquid) and one or both of a liquid substance or a dry substance (e.g., reagent) and may be at least partially homogenized. The duration and force applied to create the mixture may be based on the substances and the total combined volume of the substances in the vial, for example. The mixing process is controlled by the control system using a computer program that is specific to the substances being mixed and the assay to be performed using the substances. The volume and flow rate of the air to be aspirated, the depth of the probe inside the liquid to dispense the air, and the number of times that this procedure happens is controlled by the control system. 
     In an example, referring to  FIG.  9   , the control system may control probe  44  to move diluent from a first vial  95  into a second vial  96  containing liquid substance and/or to a third vial  97  containing lyophilized (dry/solid) substance. Although a liquid diluent and a dry substance are used in these examples, the probe may be used to mix any two or more substances. The probe that moved the substances may also be used to mix the substances Referring to  FIGS.  10  and  11   , to mix liquid substance and the other substance according to process  102 , the control system may control the probe to move ( 102   d ) within the vial so that it is not within the substances to be mixed, to aspirate ( 102   e ) air into a shaft of the probe from inside the vial; and to dispense ( 102   f ) the air  103  ( FIG.  10   ) in the direction of arrow  104  from shaft  46  into the vial with enough force to create an air flow rate to mix the two substances to a level that is deemed sufficient, e.g., mixed in such a way that the analytical performance of these homogenized substances is equivalent to the standard assay, as experimentally assessed. Parameters relating to air volume and flow rate may be obtained from previous experimentation and may be used as information for software commands used in the mixing/homogenization procedure. The air turbulence in the vial resulting from the air flow performs the mixing. 
     In some implementations, the shaft may be above the substances to be mixed while dispensing the air. In some implementations, the shaft may be immersed in the substances to be mixed while dispensing the air. For example, the tip of the shaft may at or near a bottom of the vial to dispense air into the vial. For example, the tip of the shaft may be in a middle of the substances to be mixed while dispensing the air. 
     After all the air is dispensed from the probe, additional mixing may be required. The mixing procedure for each substance may be written in the software executed by the control system—for example, it is known how many cycles of mixing are needed from previous experiments for each specific substance or combination of substances. The mixing protocol may be specifically established and fixed for each specific material/assay and written in its specific preparation procedure software, which may be executed by the control system. 
     In the case of additional mixing, operations  102   d  to  102   g  may be repeated as many times as necessary to achieve mixing of the substances in such way that the analytical performance of the homogenized substances is equivalent to the standard assay, as experimentally assessed. In some examples, the mixing process may be repeated any number of times as needed based on previous experimentation. 
     In some implementations, the air for mixing may be aspirated from outside the vial and introduced into the vial and used, as described above, to implement the mixing. For example, the control system may control the probe to move out of for example, to retract from—the vial, to aspirate air into a shaft of the probe from outside the vial; to cause the shaft to reenter the vial containing the two substances, and to dispense the air from the shaft into the vial. These operations may be repeated as necessary. Pressure equilibration may be performed, as necessary. 
     The use of air may be advantageous at least because the force to mix/homogenize substances may be stronger than with liquid—e.g., a higher volume of air may be used than liquid and higher flow rate of air may be used than with liquid. 
     Mixing using air may produce air bubbles. In some cases, the air bubbles burst quickly on their own if the mixture does not contain chemicals that stabilize the bubbles. If the bubbles do not burst on their own in less than a predefined time period, such as 60 seconds or 30 seconds, the bubbles are considered stable. Under these circumstances, air may not be the best way to mix the substances. 
     Whether mixing/homogenization resulting in air bubbles in substance(s) is used may be controlled by a mixing procedure specifically written for each substance and included in the software for the assay using the substance that is executed by the control system. The volume and flow rate of the air to be aspirated, the depth of the probe inside the liquid to dispense the air, its flow rate, and the volume and the number of times that this procedure occurs also may be specified in the software. 
     In implementations where air is determined not to be the best method of mixing, substances may be mixed by aspirating the mixture from the container to be mixed into a probe and reintroducing the aspirated mixture into the container. Referring to  FIGS.  12  and  13   , prior to example mixing process  105 , probe  44  may have been controlled to aspirate diluent or another substance  100  into its shaft, to cause the shaft to enter the interior of the vial  96  containing reagent  101 , and to dispense the diluent or another substance  100  into the vial. To mix the substances in accordance with process  105 , the control system may control the shaft  46  to move ( 105   d ) into the mixture of substances in the vial so that at least the probe&#39;s tip  48  ( FIG.  3   ) is immersed in the substances. The probe is controllable to aspirate ( 105   e ) substances for example, the combination of substances contained in the vial from the vial into its shaft and to reintroduce/dispense ( 105   f ) the substances from the probe into the vial in order to mix the substances (diluent and the reagent in this example). These operations are represented as an example in  FIG.  12    by arrows  107 . In this example mixing process, the probe need not be removed from, or need not retract from, the vial in order to implement the mixing. Thus, while at least part of the probe&#39;s shaft remains within the vial, the control system controls the probe to dispense the content from the shaft into the vial with a velocity to mix the two substances to a level, obtained by previous experimentation, so that the analytical performance of the homogenized substances is equivalent to the standard assay, as experimentally assessed). The example mixing procedures—both with air or liquid—have been previously studied and established to produce a mixed substance that yields analytical results comparable to each specific assay. The type(s) of mixing procedures, specific for each substance/assay are written in the specific preparation procedure software for each substance/assay that is executed by the control system. 
     The turbulence in the vial resulting from reintroduction of content into the mixture of substances causes the mixing/homogenization. Operations  105   e  and  105   f  may be repeated a number of times in order to achieve a level of mixing such way that the analytical performance of the homogenized substances is equivalent to the standard assay, as experimentally assessed). The number of times the process is to be repeated, including as many times as needed, may be programmed into the control system and is based, at least in part, on the content and physical attributes of the substances, such as whether the substances are liquid or solid, their viscosities, and so forth and experimentally assessed in previous studies. The length of time for mixing may be programmed by each substance/assay specific procedure software that is executed by the control system. 
     In accordance with the above technique, substances may be aspirated into the shaft from the vial from any location (height level) within the vial. For example, referring to  FIG.  12   , the content may be aspirated from a surface layer  110 , from a middle layer  111 , or from a layer that is at or near a bottom  112  of vial  96  as shown and dispensed into different layers as experimentally assessed in previous studies. By aspirating substance from at or near a bottom  112  of the vial, the probe may better be able to capture sediment or other substance components that have separated and settled to the bottom of the vial. Such substance components may be aspirated into the shaft and reintroduced into the vial as described previously. 
     One or both of the foregoing mixing techniques may be used to periodically rem ix content within a vial. For example, mixture components in a vial may separate and settle over time. The probe may be controlled, for example based on a time schedule set by the control system, to repeat the mixing operations as needed to combat settling. The frequency of repetition may be programmed in the software for each specific substance/assay that is executed by the control system. 
     As described previously, the probe may be used to aspirate air from a vial (or other container) and/or to dispense/inject air into the vial (or other container) in order to adjust an internal pressure of the vial toward a target pressure—for example, to bring or to move the internal pressure closer to the target pressure. In this regard, during mixing, the internal pressure in some vials may increase above a target pressure. Accordingly, probe  44  or another probe may be controlled by the control system to change the pressure in a vial (or other container) containing the mixture in the manner described herein. 
     The control system described herein may be implemented using computing systems or any other computing device. The control system can be implemented, at least in part, using one or more computer program products, e.g., one or more computer program tangibly embodied in one or more information carriers, such as one or more non-transitory machine-readable media, for execution by, or to control the operation of, one or more data processing apparatus, e.g., a programmable processor, a computer, multiple computers, and/or programmable logic components. 
     A computer program can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program can be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a network. 
     Actions associated with implementing all or part of the control system can be performed by one or more programmable processors executing one or more computer programs to perform the functions described herein. All or part of the control system can be implemented using special purpose logic circuitry, e.g., an FPGA (field programmable gate array) and/or an ASIC (application-specific integrated circuit). 
     Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read-only storage area or a random-access storage area or both. Elements of a computer (including a server) include one or more processors for executing instructions and one or more storage area devices for storing instructions and data Generally, a computer will also include, or be operatively coupled to receive data from, or transfer data to, or both, one or more machine-readable storage media, such as mass storage devices for storing data, e.g., magnetic, magneto-optical disks, or optical disks. Machine-readable storage media suitable for embodying computer program instructions and data include all forms of non-volatile storage area, including by way of example, semiconductor storage area devices, e.g., EPROM, EEPROM, and flash storage area devices; magnetic disks, e.g., internal hard disks or removable disks; 
     magneto-optical disks; and CD-ROM and DVD-ROM disks. 
     Elements of different implementations described herein may be combined to form other embodiments not specifically set forth above. Elements may be left out of the structures described herein without adversely affecting their operation. Furthermore, various separate elements may be combined into one or more individual elements to perform the functions described herein.