Patent Publication Number: US-2023149925-A1

Title: Liquid handling device

Description:
The present disclosure relates to a liquid handling device, methods of operating a liquid handling device, a method of performing a diagnostic test, a computer program and a system. 
     BACKGROUND 
     Diagnostic tests, such as immunoassays, are often used for the detection of a specific analyte within a sample. For example, pairs of antibodies that can bind to an analyte to form a sandwich that is detectable by means of an enzyme or particulate label on one of the antibodies are well known and available for a wide range of different analytes of interest. Antibodies to a particular biomarker, such as testosterone or cortisol, may be used to test levels of these substances in saliva, blood or urine samples. The presence of the analyte is then determined using, for example, electrochemical measurements or fluorescence measurements. 
     Point-of-care detection brings a diagnostic test conveniently and immediately to a patient, allowing better and faster clinical decisions to be made. However, integration of diagnostic tests into a point-of-care device or system is challenging. Preparation of a sample for an immunoassay may require mixing of multiple solutions and reagents, with precise control of volumes and mixing times. Further, the device is ideally automated to obviate the need for a medical professional to be present. 
     Thus, there is a need to provide improved liquid handling devices capable of performing liquid handling operations for use in point-of-care diagnostic tests. 
     SUMMARY 
     This summary introduces concepts that are described in more detail in the detailed description. It should not be used to identify essential features of the claimed subject matter, nor to limit the scope of the claimed subject matter. 
     In one aspect, a liquid handling device may comprise a main chamber; a sample chamber for receiving a sample, such as a saliva, blood or urine sample; one or more measurement chambers for performing measurements on the sample; a variable pressure source conduit for connecting the main chamber to a variable pressure source; a sample chamber conduit which fluidically connects the sample chamber to the main chamber; a sample chamber conduit valve for opening and closing the sample chamber conduit; a respective measurement chamber conduit for each measurement chamber, wherein each respective measurement chamber conduit fluidically connects the respective measurement chamber to the main chamber; and a respective measurement chamber conduit valve for opening and closing each respective measurement chamber conduit. 
     The variable pressure source conduit may be connected to the main chamber at the top of the main chamber, to reduce the likelihood of liquids in the main chamber entering the variable pressure source conduit and variable pressure source. 
     The main chamber and/or one or more of the one or more measurement chambers may comprise a reagent, as described below. 
     The liquid handling device may be for performing a diagnostic test on a sample. 
     The liquid handling device allows a sample to be transferred from the sample chamber into the main chamber by reducing the pressure in the main chamber relative to the sample chamber. Precise control of the volume of sample transferred into the main chamber is possible by controlling the pressure change in the main chamber. In the main chamber, the sample may react or mix with a reagent. The device allows the sample to be held in the main chamber for as long as necessary, for example for a duration of time needed to complete a reaction with a reagent. This may not be readily achievable with known fluid handling devices, such as conventional microfluidic devices. 
     The sample may then be transferred from the main chamber to the measurement chamber where it is held while a measurement is performed, for example as part of a diagnostic test such as an immunoassay. Again, precise control of the volume of sample transferred into the measurement chamber and residence time in the measurement chamber are possible. 
     The liquid handling device may be provided with or without a variable pressure source. That is to say that a variable pressure source may be integrated into the liquid handling device, but is preferably reversibly connected to the liquid handling device and as such may be provided separately. 
     A variable pressure source is a pressure source that can apply or provide both positive and negative pressure changes. For example, the variable pressure source may be a syringe and may be controlled by a stepper motor. Other variable pressure sources and ways of controlling variable pressure sources are known to the skilled person. 
     The liquid handling device is not limited to having only one main chamber or only one variable pressure source. 
     The main chamber may be arranged to receive a fluid from the sample chamber when the sample chamber conduit valve is open and a negative pressure change is applied to the main chamber via the variable pressure source conduit, and the one or more measurement chambers are arranged to receive the fluid from the main chamber when the respective measurement chamber conduit valves are open and a positive pressure change is applied to the main chamber via the variable pressure source conduit. 
     The liquid handling device may further comprise one or more reagent chambers; a respective reagent chamber conduit for each reagent chamber, wherein the respective reagent chamber conduit fluidically connects the respective reagent chamber to the main chamber; and a respective reagent chamber conduit valve for opening and closing each respective reagent chamber conduit. 
     The reagent chambers may store reagents such as an antibody or protein solution, antibody or protein powder, buffer solution, an enzyme substrate such as 3,3′,5,5′-tetramethylbenzidine “TMB,” and so on, for mixing or reacting with the sample in order to facilitate a measurement on the sample in the measurement chamber, for example to perform a diagnostic test on the sample. 
     The reagents in the reagent chambers may be readily mixed with the sample by controlling pressure changes in the liquid handling device. By providing a main chamber surrounded by one or more reagent chambers, the device facilitates complex mixing operations, for example operations with multiple steps each requiring precise volume control and timing that may not be readily achieved using known fluid handling devices. 
     A reagent chamber may also be known as an assay chamber. 
     The one or more measurement chambers may comprise a first measurement chamber for performing a first measurement on the sample and a second measurement chamber for performing a second measurement on the sample. As such, the liquid handling device further comprises a first respective measurement chamber conduit which fluidically connects the first measurement chamber to the main chamber; a second respective measurement chamber conduit which fluidically connects the second measurement chamber to the main chamber; a first respective measurement chamber conduit valve for opening and closing the first respective measurement chamber conduit; and a second respective measurement chamber conduit valve for opening and closing the second respective measurement chamber conduit. 
     As such, a single liquid handling device may be configured to receive only one sample in the sample chamber yet perform multiple measurements or diagnostic tests for determining multiple properties of the sample. 
     The one or more reagent chambers may comprise one or more first dedicated reagent chambers for reagents to be used only in a diagnostic test to be performed in the first measurement chamber, one or more second dedicated reagent chambers for reagents to be used only in a diagnostic test to be performed in the second measurement chamber, and one or more shared reagent chambers for reagents to be used in the diagnostic tests to be measured in both the first and second measurement chambers. 
     Ordinarily, separate measurement chambers would each require their own separate reagent sources, however, by providing a shared reagent chamber that provides a reagent, such as a buffer solution, common to two separate diagnostic tests or measurements, a more compact liquid handling device may be provided. At the same dedicated reagent chambers store reagents, such as specific antibodies or proteins, that may be selectively mixed with the sample for particular diagnostic tests or measurements, providing the device with a broader range of functionality. 
     The liquid handling device comprising one or more reagent chambers may further comprise a mixing chamber for mixing the sample with a reagent from one of the one or more reagent chambers. As such, the device also comprises a mixing chamber conduit, wherein the mixing chamber conduit fluidically connects the mixing chamber to the main chamber; and a mixing chamber conduit valve for opening and closing the mixing chamber conduit. 
     Once a reagent is combined with the sample, the resulting combination may be shuttled (transferred back and forth) between the main chamber and mixing chamber to accelerate mixing of the reagent and sample (homogenise the reagent and sample) or accelerate dissolution of the reagent in the sample or other liquid. 
     The liquid handling device may further comprise a waste chamber and a waste chamber conduit, wherein the waste chamber conduit fluidically connects the waste chamber to the main chamber. 
     The waste chamber may be used to safely store excess sample and/or reagents, for example after the liquid handling device has been used to perform a measurement on the sample. Further, sample may be overprovided to the main chamber, and then transferred into another chamber such as a mixing chamber in a precise quantity, while the excess sample is expelled to the waste chamber. The precisely measured sample can then be returned to the main chamber with a precise known volume. 
     The liquid handling device may further comprise a waste chamber conduit valve for opening and closing the waste chamber conduit. Alternatively, the waste chamber conduit may fluidically connect the waste chamber to the main chamber via the measurement chamber. Thus, sample can be transferred directly from the measurement chamber to the waste chamber after a measurement has been performed. 
     At least one of the one or more measurement chambers may comprise a plurality of electrodes. The plurality of electrodes may be for performing an electrochemical measurement. Alternatively or in addition, at least one of the one of more measurement chambers may comprise an element for performing an optical measurement, such as a window. In general, each measurement chamber may be configured for any type of measurement: electrochemical, optical (photometry, fluorescence, imaging), magnetic (magnetic field sensor) and/or thermometric (temperature sensor). 
     Each conduit valve may be a pinch valve. A pinch valve may be operated by an external actuator that selectively applies pressure to the pinch valve to open or close it. Optionally, the conduit valves may be configured in a circular array, so that they can be operated by an actuator with a circular array of actuation elements. A pinch valve is a valve which uses a pinching effect to obstruct fluid flow. 
     The conduit valves of the devices described above may be configured such that only one valve is open at any given time. The conduit valves of the devices described above may be closed by default. 
     The chambers of the liquid handling device may comprise gas exchange means, such as holes, air vents or a breathable sealing film. A breathable sealing film may be a hydrophobic porous sealing film with medical-grade adhesive, such as those that are available from AeraSeal® or Breathe-Easy® for cell and tissue culture where gas exchange is required. The gas exchange means is for allowing air or any other ambient gas to enter and exit each chamber to balance a pressure change resulting from liquid (such as a sample or reagent) entering the respective chambers, although this is not essential. Depending on the chamber, the chamber may be opened to the air (for example have an unsealed top), the chamber may have an air vent open to the outside, a fluid port or channel may act as an air vent, or the chamber could be vented via a venting valve connected to the pressure source conduit (for example, in the case of a main chamber). 
     The liquid handling device may be made from conventional materials known to the skilled person such as glass, silicon, polydimethylsiloxane (PDMS) or any thermoplastic (such as polymethylmethacrylate (PMMA), polycarbonate (PC), cyclic olefin copolymer (COO), polypropylene (PP)) using conventional methods such as chemical etching, laser etching, routing or moulding. 
     In another aspect, a method of operating a liquid handling device as described above may comprise opening the sample chamber conduit valve; reducing a pressure in the main chamber relative to the sample chamber; closing the sample chamber conduit valve; opening one of the respective measurement chamber conduit valves; and increasing a pressure in the main chamber relative to the respective measurement chamber. 
     Thus, after a sample has been inserted into the sample chamber, the sample may be transferred from the sample chamber to the main chamber, and then from the main chamber to the measurement chamber. 
     Pressure changes are applied via the variable pressure source conduit of the liquid handling device, and may be applied using a variable pressure source, such as a syringe or any other means suitable for applying positive and negative pressure changes, connected to the variable pressure source conduit. 
     The method of operating a liquid handling device, wherein the liquid handling device comprises one or more reagent chambers as described above, may further comprise opening the reagent chamber conduit valve corresponding to one of the one or more reagent chambers; reducing a pressure in the main chamber relative to the one of the one or more reagent chambers; and closing the reagent chamber conduit valve corresponding to the one of the one or more reagent chambers. 
     Thus, a reagent may be transferred from a reagent chamber to the main chamber. 
     The method may further comprise, prior to reducing a pressure in the main chamber relative to the one of the one or more reagent chambers, increasing a pressure in the main chamber relative to the one of the one or more reagent chambers in order to transfer a liquid in the main chamber, such as a sample, into the one of the one or more reagent chambers. Thus, if the one of the one or more reagent chambers comprises a dried or powdered reagent, a liquid in the main chamber can be used to suspend or dissolve the reagent and then transfer it into the main chamber. 
     When the liquid handling device comprises a mixing chamber as described above, the method of operating a liquid handling device may further comprise opening the mixing chamber conduit valve; increasing a pressure in the main chamber relative to the mixing chamber; reducing a pressure in the main chamber relative to the mixing chamber and closing the mixing chamber conduit valve. 
     Thus, a mixture, such as a mixture of a sample and a reagent, may be shuttled between the main chamber and mixing chamber to accelerate mixing of the reagent and sample (e.g. homogenise reagent and sample) or accelerate dissolution of the reagent in the sample. 
     The method may further comprise repeating increasing a pressure in the main chamber and reducing a pressure in the main chamber one or more times before closing the mixing chamber conduit valve. 
     When the liquid handling device comprises a waste chamber, waste chamber conduit and waste chamber conduit valve as described above, the method of operating a liquid handling device may further comprise opening the waste chamber conduit valve; increasing a pressure in the main chamber relative to the waste chamber; and closing the waste chamber conduit valve. The method may yet further comprise closing the one of the respective measurement chamber conduit valves before opening the waste chamber conduit valve. 
     Thus, liquid in the main chamber may be transferred to the waste chamber where it may be safely stored, for example after the liquid handling device has been used to perform a measurement on the sample. 
     When the liquid handling device comprises a waste chamber and waste chamber conduit fluidically connecting the waste chamber to the main chamber via the measurement chamber the method of operating a liquid handling device may further comprise increasing a pressure in the main chamber relative to the waste chamber after performing a measurement on the sample. 
     Thus, liquid in the measurement chamber may be transferred to the waste chamber where it may be safely stored, for example after the liquid handling device has been used to perform a measurement on the sample. 
     When the one or more measurement chambers comprise a plurality of electrodes, the method of operating a liquid handling device may further comprise performing an electrochemical measurement on a sample using the plurality of electrodes. 
     When each conduit valve of the liquid handling device is a pinch valve, the method of operating a liquid handling device may further comprise opening or closing at least one of the pinch valves by operating an actuator. The pinch valves may be configured to only open one-at-a-time (i.e. only one pinch valve is open at any one time). 
     As will be understood, the methods described above can be performed in combination with each other, and in many different orders or multiple times, as required for a given diagnostic test. The order of each method is not limited to the order in which the features are presented above, and one method need not be completed before another method is performed. For example, a method for mixing may be performed after a sample and reagent are introduced into the main chamber but before at least a portion of the sample is transferred to the measurement chamber. 
     In another aspect, a method of performing a diagnostic test using a liquid handling device as described above comprises filling the sample chamber with a sample and performing one or more of the methods described above. Optionally, the liquid handling device comprises one or more reagent chambers and each of the one or more reagent chambers comprises a respective reagent for the diagnostic test. 
     In another aspect, a method of operating a liquid handling device may comprise opening one of the respective auxiliary chamber conduit valves and increasing or reducing the pressure in the main chamber relative to the respective auxiliary chamber by a predetermined amount, thereby enabling transfer of a metered volume of a liquid between the main chamber and the respective auxiliary chamber. As such, the liquid handling device comprises a main chamber; one or more auxiliary chambers; a respective auxiliary chamber conduit for each auxiliary chamber, wherein each auxiliary chamber conduit fluidically connects the respective auxiliary chamber to the main chamber and a respective auxiliary chamber conduit valve for opening and closing each respective auxiliary chamber conduit. The use of predetermined pressure changes enables transfer of precise volumes of liquid. 
     Increasing or reducing the pressure in the main chamber relative to the respective auxiliary chamber by a predetermined amount may comprise applying a predetermined pressure change for a predetermined period of time. 
     When the pressure in the main chamber is increased, transfer of a metered volume of a liquid from the main chamber to the respective auxiliary chamber is enabled. When the pressure in the main chamber is reduced, transfer of a metered volume of a liquid from the respective auxiliary chamber to the main chamber is enabled. 
     When the liquid handling device further comprises a waste chamber; a waste chamber conduit, wherein the waste chamber conduit fluidically connects the waste chamber to the main chamber, and a waste chamber conduit valve for opening and closing the waste chamber conduit, the method may further comprise closing the one of the respective auxiliary chamber conduit valves; opening the waste chamber conduit valve and increasing a pressure in the main chamber relative to the waste chamber thereby enabling transfer of liquid in the main chamber to the waste chamber. The method may yet further comprise closing the waste chamber conduit valve. 
     In this way, sample may be overprovided to the main chamber, and then transferred into another chamber such as a mixing chamber in a precise quantity, while the excess sample is expelled to the waste chamber. The precisely measured sample can then be returned to the main chamber with a precisely known volume. 
     In another aspect, a computer program may comprise computer-executable instructions which, when executed by a system, cause the system to perform the any of the methods described above. 
     In another aspect, a system may comprise a processor configured to execute a computer program comprising computer-executable instructions which, when executed by a system, cause the system to perform any of the methods described above. 
     A system may be a point-of-care system or diagnostic system and/or may be for performing a diagnostic test on a sample. 
     The system may further comprise one or more of a variable pressure source configured to connect to a liquid handling device; a variable pressure source controller to control the variable pressure source; an actuator configured to selectively open or close each of the plurality of pinch valves and a liquid handling device as described above. The processor may be configured to control the variable pressure source controller to control the variable pressure source in accordance with any of the above described methods. The system may further comprise memory for storing the computer program. 
     The system may comprise an electrovalve (also known as an electrically operated valve) directly connected to the variable pressure source in a separate pneumatic circuit. The electrovalve may be configured as a venting valve to allow the pressure source to be vented between consecutive operations. That is, the electrovalve may be configured to selectively connect the pressure source to the ambient atmosphere, so that the pressure source can be vented in preparation for an operation. For example, if the pressure source is a syringe pump, when the syringe pump is connected to the ambient atmosphere by the electrovalve, the syringe position may be moved or changed in preparation for an operation without applying a pressure change to the liquid handling device. The electrovalve may also be used to vent pressure from the chambers of the device. For example, the main chamber may be connected to the syringe pump and the vent valve circuit via a T-shape pneumatic connector. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG.  1    illustrates a liquid handling device comprising a main chamber, sample chamber, variable pressure source and one or more measurement chambers; 
         FIG.  2    illustrates a liquid handling device according to  FIG.  1   , further comprising one or more reagent chambers; 
         FIG.  3    illustrates a liquid handling device according to  FIG.  1   , comprising first and second measurement chambers; 
         FIG.  4    illustrates a liquid handling device according to  FIG.  3   , further comprising first and second dedicated reagent chambers and a shared reagent chamber; 
         FIG.  5    illustrates a liquid handling device according to  FIG.  1   , further comprising a mixing chamber and a one or more dedicated reagent chambers; 
         FIG.  6    illustrates a liquid handling device according to  FIG.  1   , further comprising a waste chamber; 
         FIG.  7    illustrates a liquid handling device according to  FIG.  1   , further comprising a waste chamber; 
         FIG.  8    illustrates a liquid handling device comprising a circular array of pinch valves; 
         FIG.  9    illustrates a flow diagram for a method for transferring sample to a measurement chamber; 
         FIG.  10    illustrates a flow diagram for a method for transferring reagent to a main chamber; 
         FIG.  11    illustrates a flow diagram for a method for mixing liquids; 
         FIG.  12    illustrates a flow diagram for a method for transferring liquid to a waste chamber; 
         FIG.  13    illustrates a flow diagram for a method for performing an electrochemical measurement; 
         FIG.  14    illustrates a flow diagram for a method of operating a liquid handling device; 
         FIG.  15    illustrates a flow diagram for a method of operating a liquid handling device; 
         FIG.  16    illustrates a flow diagram for a method of performing a diagnostic test; 
         FIGS.  17 A and  17 B  illustrate flow diagrams for methods of metering; 
         FIG.  18    illustrates a flow diagram for a method of metering; 
         FIG.  19    illustrates a diagnostic system; and 
         FIG.  20    illustrates a block diagram of a diagnostic system. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    illustrates a liquid handling device  100 . The liquid handling device  100  comprises a main chamber  102 ; a sample chamber  104  for receiving a sample; one or more measurement chambers  106   a / 106   b  for performing measurements on the sample; a variable pressure source conduit  110  connecting the main chamber  102  to a variable pressure source  108 ; a sample chamber conduit  112  which fluidically connects the sample chamber  104  to the main chamber  102 ; a sample chamber conduit valve  116  for opening and closing the sample chamber conduit  112 ; a respective measurement chamber conduit  114   a / 114   b  for each measurement chamber  106   a / 106   b , wherein each respective measurement chamber conduit  114   a / 114   b  fluidically connects the respective measurement chamber  106   a / 106   b  to the main chamber  102 ; and a respective measurement chamber conduit valve  118   a / 118   b  for opening and closing each respective measurement chamber conduit  114   a / 114   b . The variable pressure source conduit  110  is connected to the main chamber  102  at the top of the main chamber. 
     The main chamber  102  is arranged to receive a fluid from the sample chamber  104  when the sample chamber conduit valve  116  is open and a negative pressure change is applied to the main chamber  102  via the variable pressure source conduit  110 . Further, the one or more measurement chambers  106   a / 106   b  are arranged to receive the fluid from the main chamber  102  when the respective measurement chamber conduit valves  118   a / 118   b  are open and a positive pressure change is applied to the main chamber  102  via the variable pressure source conduit  110 . 
     The measurement chambers  106   a / 106   b  each comprise a plurality of electrodes  138  (not illustrated in  FIG.  1   ). 
       FIG.  2    illustrates a liquid handling device  100  as illustrated in  FIG.  1   , further comprising one or more reagent chambers  120   a / 120   b ; a respective reagent chamber conduit  122   a / 122   b  for each reagent chamber  120   a / 120   b , wherein the respective reagent chamber conduit  122   a / 122   b  fluidically connects the respective reagent chamber  120   a / 120   b  to the main chamber  102 ; and a respective reagent chamber conduit valve  124   a / 124   b  for opening and closing each respective reagent chamber conduit  122   a / 122   b.    
       FIG.  3    illustrates a liquid handling device  100  as illustrated in  FIG.  1   , further comprising two measurement chambers  106   a / 106   b . The two measurement chambers  106   a / 106   b  are known as a first measurement chamber  106   a  for performing a first measurement on the sample and a second measurement chamber  106   b  for performing a second measurement on the sample. The liquid handling device  100  further comprises a first respective measurement chamber conduit  114   a  which fluidically connects the first measurement chamber  106   a  to the main chamber  102 ; a second respective measurement chamber conduit  114   b  which fluidically connects the second measurement chamber  106   b  to the main chamber  102 ; a first respective measurement chamber conduit valve  118   a  for opening and closing the first respective measurement chamber conduit  114   a ; and a second respective measurement chamber conduit valve  118   b  for opening and closing the second respective measurement chamber conduit  114   b.    
       FIG.  4    illustrates a liquid handling device  100  as illustrated in  FIG.  3   , further comprising first and second dedicated reagent chambers  120   c / 120   d  and a shared reagent chamber  120   e  with respective conduits  122   c / 122   d / 122   e  and conduit valves  124   c / 124   d / 124   e.    
     The first dedicated reagent chamber  120   c  is for reagents to be used only in a diagnostic test to be performed in the first measurement chamber  106   a , the second dedicated reagent chamber  120   d  is for reagents to be used only in a diagnostic test to be performed in the second measurement chamber  106   b , and the shared reagent chamber  120   e  is for reagents to be used in diagnostic tests to be measured in both the first and second measurement chambers  106   a / 106   b.    
       FIG.  5    illustrates a liquid handling device  100  as illustrated in  FIG.  2   , further comprising a mixing chamber  126  for mixing a sample with a reagent from one of one or more reagent chambers  120   a / 120   b ; a mixing chamber conduit  128 , wherein the mixing chamber conduit  128  fluidically connects the mixing chamber  126  to the main chamber  102 ; and a mixing chamber conduit valve  130  for opening and closing the mixing chamber conduit  128 . 
       FIG.  6    illustrates a liquid handling device  100  as illustrated in  FIG.  1   , further comprising a waste chamber  132  and a waste chamber conduit  134 , wherein the waste chamber conduit  134  fluidically connects the waste chamber  132  to the main chamber  102 . The liquid handling device  100  further comprises a waste chamber conduit valve  136  for opening and closing the waste chamber conduit  134 . 
       FIG.  7    illustrates a liquid handling device  100  as illustrated in  FIG.  1   , further comprising a waste chamber  132  with a different configuration to that of  FIG.  6   , wherein a waste chamber conduit  134  fluidically connects the waste chamber  132  to the main chamber  102  via the measurement chamber  106   a . In contrast to the liquid handling device  100  illustrated in  FIG.  6   , no valve for controlling flow in the waste chamber conduit  134  is provided. 
       FIG.  8    illustrates a liquid handling device  100  as illustrated in  FIG.  3   , further comprising a first dedicated reagent chamber  120   c  for a reagent to be used only in a diagnostic test to be performed in a first measurement chamber  106   a ; a second dedicated reagent chamber  120   d  for a reagent to be used only in a diagnostic test to be performed in the second measurement chamber  106   b ; two shared reagent chambers  120   e  for reagents to be used in the diagnostic tests to be measured in both the first and second measurement chambers  106   a / 106   b ; and two mixing chambers  126 . Conduits  122   c / 122   d / 122   e / 128  and conduit valves  124   c / 124   d / 124   e / 130  for the corresponding chambers are provided. 
     The liquid handling device  100  further comprises a first waste chamber  132   a  and a second waste chamber  132   b . A first waste chamber conduit  134   a  fluidically connects the first waste chamber  132   a  to the first measurement chamber  106   a . A second waste chamber conduit  134   b  fluidically connects the second waste chamber  132   b  to the main chamber  102  and a third waste chamber conduit  134   c  fluidically connects the second waste chamber  132   b  to the second measurement chamber  106   b . A second waste chamber conduit valve  136  is configured to open and close the second waste chamber conduit  134   b.    
     The variable pressure source conduit  110  is connected to a variable pressure source  108 . The conduit valves are pinch valves and are configured in a circular array. Each measurement chamber  106   a / 106   b  comprises a plurality of electrodes  138 . 
     The chambers of the liquid handling device  100  comprise gas exchange holes for allowing air or any other ambient gas to enter and exit each chamber to balance a pressure change resulting from liquid (such as sample or reagent) entering the respective chambers. The gas exchange holes are not essential, while other gas exchange means such as air vents can be used instead or in addition to holes. 
       FIG.  9    illustrates a flow diagram for a method of operating any of the liquid handling devices  100  described above. The method is for transferring a sample from a sample chamber  104  to a main chamber  102  and then from the main chamber  102  to the one of the measurement chambers  106   a / 106   b.    
     The method comprises opening  202  the sample chamber conduit valve  116 ; reducing  204  a pressure in the main chamber  102  relative to the sample chamber  104 ; closing  206  the sample chamber conduit valve  116 ; opening  208  one of the measurement chamber conduit valves  118   a / 118   b ; and increasing  210  a pressure in the main chamber  102  relative to the respective measurement chamber  106   a / 106   b . The method may further comprise closing  236  the one of the measurement chamber conduit valves  118   a / 118   b , although this is not essential. 
     As such, sample in the sample chamber  104  may be transferred from the sample chamber  104  to the main chamber  102 , and then from the main chamber  102  to one of the measurement chambers  106   a / 106   b.    
       FIG.  10    illustrates a flow diagram for a method of operating any of the liquid handling devices  100  described above and comprising one or more reagent chambers  120   a/b/c/d/e  (including a dedicated reagent chamber  120   c / 120   d  and shared reagent chamber  120   e ). The method is for transferring a reagent from one of one or more reagent chambers  120   a/b/c/d/e  to the main chamber  102 . 
     The method comprises opening  212  the reagent chamber conduit valve  124   a/b/c/d/e  corresponding to one of the one or more reagent chambers  120   a/b/c/d/e ; reducing  214  a pressure in the main chamber  102  relative to the one of the one or more reagent chambers  120   a/b/c/d/e ; and closing  216  the reagent chamber conduit valve  124   a/b/c/d/e  corresponding to the one of the one or more reagent chambers  120   a/b/c/d/e.    
     As such, a reagent in one of the one or more reagent chambers  120   a / 120   b  may be transferred from the respective reagent chamber  120   a/b/c/d/e  to the main chamber  102 . 
       FIG.  11    illustrates a flow diagram for a method of operating any of the liquid handling devices  100  described above and comprising a mixing chamber  126 . The method is for mixing liquids, such as a sample and a reagent, in the liquid handling device  100 . 
     The method comprises opening  218  the mixing chamber conduit valve  130 ; increasing  220  a pressure in the main chamber  102  relative to the mixing chamber  126 ; reducing  222  a pressure in the main chamber  102  relative to the mixing chamber  126 ; and closing  224  the mixing chamber conduit valve  130 . 
     As such, a mixture of liquids, such as a sample and a reagent, may be shuttled between the main chamber  102  and mixing chamber  126 , thereby further mixing the liquids. 
     As also illustrated in  FIG.  11   , the method further comprises repeating increasing  220  a pressure in the main chamber  102  and reducing  222  a pressure in the main chamber  102  one or more times before closing  224  the mixing chamber conduit valve  130 . This may further increase the degree of mixing of liquids in the liquid handling device, until the liquids are homogeneously mixed. 
       FIG.  12    illustrates a flow diagram for a method of operating any of the liquid handling devices  100  described above and comprising a waste chamber  132  and waste chamber conduit valve  136 . The method is for transferring liquid in the main chamber  102  of the liquid handling device  100  to a waste chamber  132  where it can be safely stored. 
     The method comprises opening  226  the waste chamber conduit valve  136 ; increasing  228  a pressure in the main chamber  102  relative to the waste chamber  132 ; and closing  230  the waste chamber conduit valve  136 . 
     As such, liquid in the main chamber  102  may be transferred to the waste chamber  132 . 
     Also disclosed is a method of operating any of the liquid handling devices  100  described above and comprising a waste chamber  132  connected to the measurement chamber  138  via a waste chamber conduit  134   a / 134   c , wherein the method comprises increasing  232  a pressure in the main chamber  102  relative to the waste chamber  132  after performing a measurement on the sample. The method is for transferring liquid in the measurement chamber  138  of the liquid handling device  100  to a waste chamber  132 , where it can be safely stored after a measurement has been performed. This method is part of the method illustrated in the flow diagram of  FIG.  15   , discussed below, but does not need to be conducted in conjunction with the rest of the method illustrated in  FIG.  15   . 
       FIG.  13    illustrates a flow diagram for a method of operating any of the liquid handling devices  100  described above and comprising a plurality of electrodes  138  in a measurement chamber  106   a / 106   b . The method comprises opening  208  the measurement chamber conduit valve  118   a / 118   b  corresponding to the respective measurement chamber  106   a / 106   b ; increasing  210  a pressure in the main chamber  102  relative to the respective measurement chamber  106   a / 106   b ; and performing  234  an electrochemical measurement on the sample using the plurality of electrodes  138 . The method may comprise closing  236  the measurement chamber conduit valve  118   a / 118   b  before or after performing  234  the electrochemical measurement. The method is for performing a measurement on a sample as part of a diagnostic test. 
     The above-described methods can be performed in combination with each other, and in many different orders or multiple times, as required for a given diagnostic test. One method need not be completed before another method is performed. 
     For example,  FIG.  14    illustrates a flow diagram for a method of operating the liquid handling device  100  illustrated in  FIG.  5   , the method comprising a combination of the above-described methods. The method is for mixing a sample with a reagent and transferring it to a measurement chamber, where a measurement can be performed on the sample. The valves of the liquid handling device  100  are closed by default i.e. in a closed configuration unless opened as part of the method. 
     The method comprises:
         a) opening  202  the sample chamber conduit valve  116 ;   b) reducing  204  a pressure in the main chamber  102  relative to the sample chamber  104 ;   c) closing  206  the sample chamber conduit valve  116 ;   d) opening  218  the mixing chamber conduit valve  130 ;   e) increasing  220  a pressure in the main chamber  102  relative to the mixing chamber  126 ;   f) closing  224  the mixing chamber conduit valve  130 ;   g) opening  212  the reagent chamber conduit valve  124   a/b/c/d/e  corresponding to one of the one or more reagent chambers  120   a/b/c/d/e;      h) reducing  214  a pressure in the main chamber  102  relative to the one of the one or more reagent chambers  120   a/b/c/d/e;      i) closing  216  the reagent chamber conduit valve  124   a/b/c/d/e  corresponding to the one of the one or more reagent chambers  120   a/b/c/d/e;      j) opening  218  the mixing chamber conduit valve  130 ;   k) increasing  220  a pressure in the main chamber  102  relative to the mixing chamber  126 ;   l) reducing  222  a pressure in the main chamber  102  relative to the mixing chamber  126 ;   m) closing  224  the mixing chamber conduit valve  130 ;   n) opening  208  one of the respective measurement chamber conduit valves  118   a / 118   b;      o) increasing  210  a pressure in the main chamber  102  relative to the respective measurement chamber  106   a / 106   b ; and   p) closing  236  one of the respective measurement chamber conduit valves  118   a / 118   b.          

     When a sample has been inserted into the sample chamber  104  and the one of the one or more reagent chambers  120   a/b/c/d/e  comprises a reagent, the method achieves the following (each letter corresponding to the above method step with the same letter):
         a) the sample chamber conduit valve  116  is opened;   b) the sample is transferred from the sample chamber  104  into the main chamber  102 ;   c) the sample chamber conduit valve  116  is closed;   d) the mixing chamber conduit valve  130  is opened;   e) the sample is transferred from the main chamber  102  into the mixing chamber  126 ;   f) the mixing chamber conduit valve  130  is closed;   g) the reagent chamber conduit valve  124   a/b/c/d/e  corresponding to one of the one or more reagent chambers  120   a/b/c/d/e  and holding the reagent is opened;   h) the reagent is transferred from the one of the one or more reagent chambers  120   a/b/c/d/e  into the main chamber  102 ;   i) the reagent chamber conduit valve  124   a/b/c/d/e  corresponding to the one of the one or more reagent chambers  120   a/b/c/d/e  is closed;   j) the mixing chamber conduit valve  130  is opened;   k) the reagent is transferred from the main chamber  102  into the mixing chamber  126 —the mixing chamber  126  now comprises a mixture of the sample and the reagent;   l) the sample/reagent mixture is transferred into the main chamber  102  from the mixing chamber  126 , increasing the homogeneity of the mixture;   m) the mixing chamber conduit valve  130  is closed;   n) one of the measurement chamber conduit valves  118   a / 118   b  is opened;   o) the sample/reagent mixture is transferred from the main chamber  102  into the respective measurement chamber  106   a / 106   b ; and   p) the one of the measurement chamber conduit valves  118   a / 118   b  is closed.       

     In another example combining the above-described method steps,  FIG.  15    illustrates a flow diagram for a method of operating the liquid handling device  100  illustrated in  FIG.  8   . The method is for performing a measurement on a sample as part of a diagnostic test. 
     The valves of the liquid handling device  100  are closed by default i.e. in a closed configuration unless opened as part of the method. 
     The method comprises:
         a) opening  202  the sample chamber conduit valve  116 ;   b) reducing  204  a pressure in the main chamber  102  relative to the sample chamber  104 ;   c) closing  206  the sample chamber conduit valve  116 ;   d) opening  212  the reagent chamber conduit valve  124   a/b/c/d/e  corresponding to one of the one or more reagent chambers  120   a/b/c/d/e;      e) reducing  214  a pressure in the main chamber  102  relative to the one of the one or more reagent chambers  120   a/b/c/d/e;      f) closing  216  the reagent chamber conduit valve  124   a/b/c/d/e  corresponding to the one of the one or more reagent chambers  120   a/b/c/d/e;      g) opening  218  the mixing chamber conduit valve  130 ;   h) increasing  220  a pressure in the main chamber  102  relative to the mixing chamber  126 ;   i) reducing  222  a pressure in the main chamber  102  relative to the mixing chamber  126 ;   j) increasing  220  a pressure in the main chamber  102  relative to the mixing chamber  126 ;   k) reducing  222  a pressure in the main chamber  102  relative to the mixing chamber  126 ;   l) closing  224  the mixing chamber conduit valve  130 ;   m) opening  208  the second measurement chamber conduit valve  118   b;      n) increasing  210  a pressure in the main chamber  102  relative to the second measurement chamber  106   b;      o) performing  234  an electrochemical measurement using the plurality of electrodes  138  in the second measurement chamber  106   b;      p) increasing  232  a pressure in the main chamber  102  relative to the second waste chamber  132   b;      q) closing  236  the second measurement chamber conduit valve  118   b;      r) opening  226  the waste chamber conduit valve  136 ;   s) increasing  228  a pressure in the main chamber  102  relative to the second waste chamber  132   b ; and   t) closing  230  the waste chamber conduit valve  136 .       

     When a sample has been inserted into the sample chamber  104  and the one of the one or more reagent chambers  120   a/b/c/d/e  comprises a reagent, the method achieves the following (each letter corresponding to the above method step with the same letter):
         a) the sample chamber conduit valve  116  is opened;   b) the sample is transferred from the sample chamber  104  into the main chamber  102 ;   c) the sample chamber conduit valve  116  is closed;   d) the reagent chamber conduit valve  124   a/b/c/d/e  corresponding to one of the one or more reagent chambers  120   a/b/c/d/e  and holding the reagent is opened;   e) the reagent from the one of the one or more reagent chambers  120   a/b/c/d/e  is transferred into the main chamber  102 —the main chamber  102  now comprises a mixture of the sample and the reagent;   f) the reagent chamber conduit valve  124   a/b/c/d/e  corresponding to the one of the one or more reagent chambers  120   a/b/c/d/e  is closed;   g) the mixing chamber conduit valve  130  is opened;   h) the sample/reagent mixture is transferred from the main chamber  102  into to the mixing chamber  126 , increasing the homogeneity of the mixture;   i) the sample/reagent mixture is transferred from the mixing chamber  126  into the main chamber  102 , increasing the homogeneity of the mixture;   j) the sample/reagent mixture is transferred from the main chamber  102  into the mixing chamber  126 , increasing the homogeneity of the mixture;   k) the sample/reagent mixture is transferred from the mixing chamber  126  into the main chamber  102 , increasing the homogeneity of the mixture;   l) the mixing chamber conduit valve  130  is closed;   m) the second measurement chamber conduit valve  118   b  is opened;   n) a first portion of the sample/reagent mixture is transferred from the main chamber  102  into the second measurement chamber  106   b , leaving a second portion of the sample/reagent mixture in the main chamber  102 ;   o) an electrochemical measurement is performed on the first portion of the sample/reagent mixture;   p) the first portion of the sample/reagent mixture in the second measurement chamber  106   b  is transferred into the second waste chamber  132   b  via the third waste chamber conduit  134   c;      q) the second measurement chamber conduit valve  118   b  is closed;   r) the waste chamber conduit valve  136  is opened;   s) the second portion of the sample/reagent mixture in the main chamber  102  is transferred into the second waste chamber  132   b  via the second waste chamber conduit  134   b ; and   t) the waste chamber conduit valve  136  is closed to shut the first and second portions of the sample/reagent mixture in the second waste chamber  132   b.          

     Also disclosed is a method of operating any of the liquid handling devices  100  described above and comprising pinch vales. The method comprises opening or closing at least one of the pinch valves by operating an actuator. The method is for opening and closing pinch valves of a liquid handling device  100 . 
       FIG.  16    illustrates a flow diagram for a method of performing a diagnostic test using any of the liquid handling devices  100  described above. The method comprises filling  238  the sample chamber  104  with a sample and performing  240  any of the above described methods. 
       FIGS.  17 A and  17 B  illustrate flow diagrams for methods of operating a liquid handling device  100 , the liquid handling device comprising a main chamber  102 ; one or more auxiliary chambers; a respective auxiliary chamber conduit for each auxiliary chamber, wherein each auxiliary chamber conduit fluidically connects the respective auxiliary chamber to the main chamber  102 ; and a respective auxiliary chamber conduit valve for opening and closing each respective auxiliary chamber conduit. The method is for metering a volume of liquid (i.e. transferring a precise volume of liquid between chambers) by applying a predetermined pressure change for a predetermined period of time to the main chamber  102 . 
     As illustrated in  FIG.  17 A , the method comprises opening  244  one of the auxiliary chamber conduit valves and increasing  246  the pressure in the main chamber  102  relative to the respective auxiliary chamber by a predetermined amount, thereby enabling transfer of a metered volume of a liquid from the main chamber  102  to the respective auxiliary chamber. 
     Alternatively, as illustrated in the flow diagram of  FIG.  17 B , the method comprises opening  244  one of the auxiliary chamber conduit valves and reducing  248  the pressure in the main chamber  102  relative to the respective auxiliary chamber by a predetermined amount, thereby enabling transfer of a metered volume of a liquid from the respective auxiliary chamber to the main chamber  102 . 
     The one or more auxiliary chambers include at least one of a sample chamber  104 , a reagent chamber  120   a/b/c/d/e  and a mixing chamber  126 . 
       FIG.  18    illustrates a flow diagram for a method of operating a liquid handling device  100 , performed after the methods illustrated in  FIGS.  17 A and  17 B . The liquid handling device  100  further comprises a waste chamber  132 ; a waste chamber conduit  134 , wherein the waste chamber conduit  134  fluidically connects the waste chamber  132  to the main chamber  102 ; and a waste chamber conduit valve  136  for opening and closing the waste chamber conduit  134 , for example as illustrated in  FIG.  6  or  7   . The method further comprises closing  250  the one of the respective auxiliary chamber conduit valves; opening  226  the waste chamber conduit valve  136 ; increasing  228  a pressure in the main chamber  102  relative to the waste chamber  132  thereby enabling transfer of liquid in the main chamber  102  to the waste chamber  132 ; and closing  252  the one of the respective auxiliary chamber conduit valves. 
     As such, a first volume of a liquid may be overprovided to the main chamber  102 , before a precise second volume of the liquid—less than the first volume—is transferred to an auxiliary chamber. The remainder of the first volume is then transferred to the waste chamber  132 , and the precise second volume transferred to the main chamber  102 . Thus, the imprecise first volume of liquid in the main chamber  102  is replaced by a precise second volume of liquid. 
     The methods for metering illustrated in  FIGS.  17 A,  17 B and  18    (and their variations) may also be combined with the methods illustrated in  FIGS.  9  to  16    (and their variations). 
     The described methods may be implemented using computer executable instructions. A computer program product or computer readable medium may comprise or store the computer executable instructions. The computer program product or computer readable medium may comprise a hard disk drive, a flash memory, a read-only memory (ROM), a CD, a DVD, a cache, a random-access memory (RAM) and/or any other storage media in which information is stored for any duration (e.g. for extended time periods, permanently, brief instances, for temporarily buffering, and/or for caching of the information). A computer program may comprise the computer executable instructions. The computer readable medium may be a tangible or non-transitory computer readable medium. The term “computer readable” encompasses “machine readable”. 
     Thus, also disclosed is a computer program comprising computer-executable instructions which, when executed by a diagnostic system  300 , cause the diagnostic system  300  to perform any of the methods described above. 
       FIG.  19    illustrates a diagnostic system  300 . The diagnostic system  300  comprises a liquid handling device  100 , for example as illustrated in  FIG.  8   , and a docking station  302  for receiving the liquid handling device  100 . The docking station  302  comprises a housing with a slot for receiving the liquid handling device  100 . Inside the housing, the docking station includes a central bus structure, processor  304 , data processing resources such as memory  306 , variable pressure source  108 , pressure source controller  308 , actuator  310 , actuator controller  312 , display adapter  314 , display device  316 , one or more user-input device adapters  318 , one or more user-input devices  320 , such as a keyboard and/or a mouse, and one or more communications adapters  322 . The display device  316  has touch-input functionality and so also functions as a user-input device  320 . 
       FIG.  20    illustrates a block diagram of the diagnostic system  300 . The processor  304  is configured to execute the computer program which causes the diagnostic system  300  to perform any of the methods described above. The processor  304  is in communication with memory  306 , which is for storing the computer program. The processor  304  and memory  306  are connected to the central bus structure inside the docking station  302 . 
     The variable pressure source  108  is configured to connect to the liquid handling device  100 . The processor  304  is configured to control the pressure source controller  308  to control the variable pressure source  108  in accordance with any of the above described methods. The variable pressure source  108  is a syringe pump and the pressure source controller  308  is a pump controller, although other pressure sources and pressure source controllers are known to the skilled person. 
     The system  300  comprises an electrovalve directly connected to the variable pressure source  108  in a separate pneumatic circuit. This is used as a venting valve to allow the variable pressure source  108  to be vented between consecutive operations. 
     The actuator  310  and actuator controller  312  are configured to selectively open or close each of the conduit valves of the liquid handling device  100 , which are pinch valves. The processor  304  is configured to control the actuator  310  in accordance with any of the above described methods. The actuator  310  is a simple mechanical actuator that presses and releases the pinch valves to open and close them. Many other valve types and actuators are known to the skilled person. 
     The display adapter  314  is connected to the display device  316 , the one or more user-input device adapters  318  are connected to the one or more user-input devices  320 , and the one or more communications adapters  322  provide connections to other computer systems and networks. The pressure source controller  308 , actuator controller  312 , display adapter  314 , user-input device adapters  318  and communications adapters  322  connect to the central bus structure. The system  300  may be provided without the display device  316  and display adapter  314 . 
     Instead of the liquid handling device  100  illustrated in  FIG.  8   , the diagnostic system  300  may comprise any of the liquid handling devices  100  described above. 
     The embodiments of the invention shown in the drawings and described above are exemplary embodiments only and are not intended to limit the scope of the appended claims, including any equivalents as included within the scope of the claims. Various modifications are possible and will be readily apparent to the skilled person in the art. It is intended that any combination of non-mutually exclusive features described herein are within the scope of the present invention. That is, features of the described embodiments can be combined with any appropriate aspect described above and optional features of any one aspect can be combined with any other appropriate aspect.