Patent Publication Number: US-2017370825-A1

Title: Special purpose cuvette assembly and method for optical microscopy of nanoparticles in liquids

Description:
RELATED APPLICATIONS 
     This application claims priority as a continuation of U.S. patent application Ser. No. 15/194,823, filed on Jun. 28, 2016, titled “SPECIAL PURPOSE CUVETTE ASSEMBLY AND METHOD FOR OPTICAL MICROSCOPY OF NANOPARTICLES IN LIQUIDS” which claimed priority as the non-provisional of U.S. Provisional Patent Application No. 62/187,391, filed on Jul. 1, 2015, titled “SPECIAL PURPOSE CUVETTE ASSEMBLY AND METHOD FOR OPTICAL MICROSCOPY OF NANOPARTICLES IN LIQUIDS,” the disclosures of which are herein incorporated by reference in their entirety. This application is also related to U.S. patent application Ser. No. 14/730,138, filed on Jun. 3, 2015, titled “NANOPARTICLE ANALYZER,” U.S. patent application Ser. No. 15/018,532 filed on Feb. 8, 2016, titled “MULTI-CAMERA APPARATUS FOR OBSERVATION OF MICROSCOPIC MOVEMENTS AND COUNTING OF PARTICLES IN COLLOIDS AND ITS CALIBRATION”, U.S. patent application Ser. No. 15/293,180 filed on Oct. 13, 2016, titled “APPARATUS AND METHOD FOR MEASUREMENT OF GROWTH OR DISSOLUTION KINETICS OF COLLOIDAL PARTICLES”, and U.S. Provisional Patent Application No. 62/372,025, filed on Aug. 8, 2016, titled “METHOD FOR CALIBRATING INVESTIGATED VOLUME FOR LIGHT SHEET BASED NANOPARTICLE TRACKING AND COUNTING APPARATUS” the disclosures of which are herein incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a system for detecting and measuring nanoparticles in liquid samples. 
     BACKGROUND 
     Nanoparticles are ubiquitous and by far the most abundant particle-like entities in natural environments on Earth and are widespread across many applications associated with human activities. There are many types of naturally occurring nanoparticles and man-made (engineered) nanoparticles. Nanoparticles occur in air, aquatic environments, rain water, drinking water, bio-fluids, pharmaceuticals, drug delivery and therapeutic products, and a broad range of many industrial products. Nanoparticles usually occur within polydisperse assemblages which are characterized by co-occurrence of differently-sized particles. 
     Given the widespread usage of nanoparticles, the ability to control and accurately characterize their properties may be useful to many applications. Conventional methods for measuring nanoparticle properties include Nanoparticle Tracking Analysis, which uses a microscope and video camera to analyze frames of the recorded videos to track images of light reflected or scattered by the nanoparticles undergoing Brownian motion. The instrument to perform such analysis is usually comprised of a small cell, or cuvette, that enables illumination of a liquid with a very precisely defined, narrow light sheet and observation of scattered light from the nanoparticles, usually at a 90-degree angle to the light sheet, hence the cuvette must contain at least two surfaces with minimal light attenuation properties (for example optical glass). Such cuvettes are widely used in all types of optical measurements in various laboratory instruments, are easily available and have standardized internal dimensions, in the case of the prototype 10 mm×10 mm×45 mm. 
     Ideally there should be no bulk movement of the liquid when the videos are being recorded so the only particle motion is pure Brownian motion. However, due to the low thermal conductivity of glass and because of potentially considerable energy transmitted from the illuminating beam to the liquid and wall of cuvette by absorption, one can observe thermally generated micro flow of the liquid regardless of the volume of liquid in a traditional cuvette. Other sources of micro flows are possible, for example movements of the table on which the instrument is mounted that cause vibrations of the table or evaporation of the sample liquid that cools its surface. Flow can also be induced by stirring the liquid in the cuvette, or by pumping liquids in and out of the cuvette. In these and other induced flow cases, it is always desirable to arrest the flow as quickly as possible for effective and timely particle analysis. Algorithms are available to detect and remove effects of such bulk liquid movement, however, these algorithms have limitations and more accurate results are always achieved in the absence of bulk liquid movement. 
     Another desirable situation for optimal detection and processing of scattered light from nanoparticles in liquids is to minimize or eliminate backscattering of light from the wall of the cuvette that is opposite to the wall where light enters the cuvette (the back wall). Such backscattering of the incoming light beam typically broadens the illuminated region (thickening of light sheet), thus creating images that could be partially out of focus of the microscope (fuzzy images), which are not suitable for precise particle tracking. Backscattering induced broadening has an inherently inconsistent impact on the width of the light sheet and as such also causes variability in particle concentration measurements since the width of the light sheet effects the volume of sample that is being analyzed in each measurement. Secondarily deleterious light scattering effects from other reflective surfaces in the cuvette should also be minimized through use of light absorbing materials or coatings (such as black paint). 
     Another important consideration is compatibility with existing components that accurately hold the cuvette in place relative to the light sheet, control its temperature and enable stirring and or pumping of the liquid. Such stirring and/or pumping facilitates examination of multiple fresh aliquots from the same sample within the cuvette and is easily achieved with a magnetic stirring bar at the bottom of the cuvette which is driven by an external rotating magnet, or with an external pump. 
     What is needed, therefore, is an improved system that can minimize movement of the liquid while also eliminating backscatter of the light within the observation region of the cuvette. 
     SUMMARY 
     The apparatus, systems, and methods described herein elegantly solve the movement and backscatter problems and provide other improvements and benefits as will be apparent to persons of skill in the art. Accordingly, a system  10  for viewing nanoparticles is provided. The system includes a light source  15  for generating an electromagnetic energy  20  directed at a cuvette  25 , and a sensor  30  for detecting electromagnetic energy within the cuvette. The cuvette  25  is uniquely constructed and has exterior walls  35  and a floor  40  that define a volume  45 , wherein at least a portion of the exterior wall is transparent  50  to the electromagnetic energy, and wherein the volume is adapted to contain a suspension liquid and the nanoparticles. The cuvette  25  includes a viewing chamber  55  that has an upper viewing chamber wall  60  extending from the exterior wall  35  and a lower viewing chamber wall  65  extending from the exterior wall  35 , wherein the upper and lower viewing chamber walls are substantially parallel to the floor  40 . The cuvette  25  also includes a reflecting wall  70  adjacent to the upper and lower viewing chamber walls  60 ,  65 . The cuvette also has a backscatter chamber  75  separated from and in fluid communication with the viewing chamber  80 , wherein the reflecting wall  70  is adapted to reflect  85  the electromagnetic energy  20  into a backscatter chamber  75 . 
     The cuvette  25  may also have a mixing chamber  90  separated from and in fluid communication with the viewing chamber  55 , the mixing chamber including a mixing stick  100 . The reflecting wall  70  may also be connected to the lower viewing chamber wall  65  forming an angle from between 30 and 60 degrees. The reflecting wall  70  may have a highly-reflective surface  72 . The upper and lower viewing chamber  60 ,  65  may have a non-reflective surface  68 . The backscatter chamber  75  is preferably at least two times larger than the viewing chamber  55 . 
     The cuvette  25 A may be made of multiple materials to save on cost. For example, the transparent portion of the exterior walls  50  may be made of a high-quality optical glass, while a second portion of the exterior walls  35  is made of a material that is different than the transparent portion  50 . 
     To determine the zeta-potential of the nanoparticles, the upper and lower viewing chamber walls  60 ,  65  may be electrically charged  67 +,  67 − to create an electromagnetic field within the viewing chamber  55 . 
     Additional aspects, alternatives and variations as would be apparent to persons of skill in the art are also disclosed herein and are specifically contemplated as included as part of the invention. The invention is set forth only in the claims as allowed by the patent office in this or related applications, and the following summary descriptions of certain examples are not in any way to limit, define or otherwise establish the scope of legal protection. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be better understood with reference to the following figures. The components within the figures are not necessarily to scale, emphasis instead being placed on clearly illustrating example aspects of the invention. In the figures, like reference numerals designate corresponding parts throughout the different views and/or embodiments. It will be understood that certain components and details may not appear in the figures to assist in more clearly describing the invention. 
         FIG. 1  illustrates a system for detecting nanoparticles using electromagnetic energy. 
         FIG. 2  illustrates the backscatter effect that causes blurry images and volume uncertainty. 
         FIG. 3  is an isometric view of a cuvette insert that may be placed inside of a conventional cuvette. 
         FIG. 4  is a cross-sectional side view of the cuvette insert of  FIG. 3 , which illustrates the path of the electromagnetic light sheet. 
         FIG. 5  is a top view of the cuvette insert of  FIG. 3  placed inside of a conventional cuvette. 
         FIG. 6  shows that the manufacturing of the cuvette insert of  FIG. 3  can be accomplished by cutting, bending and welding or gluing thin sheets of a material such as aluminum. 
         FIG. 7  is a cross-sectional side view of an alternate embodiment of a cuvette insert that may be used. 
         FIG. 8  is a top view of the cuvette insert of  FIG. 7  inside of a conventional cuvette. 
         FIG. 9  is an isometric view of the cuvette insert of  FIG. 7  outside of a conventional cuvette. 
         FIG. 10  shows that the manufacturing of the cuvette insert of  FIG. 7  can be accomplished by cutting, bending and welding or gluing thin sheets of a material such as aluminum. 
         FIG. 11  illustrates a novel cuvette manufactured with different materials to save on cost. 
         FIG. 12  is an isometric view of an alternate embodiment of a cuvette insert that may be used to create an electric field within the viewing chamber. 
         FIG. 13  is a cross-sectional side view of the cuvette insert of  FIG. 12 , which illustrates the electrical isolation between the upper and lower viewing chamber walls. 
         FIG. 14  is a photo showing the movement of particles without the use of the cuvette/insert described herein. 
         FIG. 15  is a photo showing the movement of particles with the use of the cuvette/insert described herein. 
     
    
    
     DETAILED DESCRIPTION 
     Reference is made herein to some specific examples of the present invention, including any best modes contemplated by the inventor for carrying out the invention. Examples of these specific embodiments are illustrated in the accompanying figures. While the invention is described in conjunction with these specific embodiments, it will be understood that it is not intended to limit the invention to the described or illustrated embodiments. To the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. 
     In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. Particular example embodiments of the present invention may be implemented without some or all of these specific details. In other instances, process operations well known to persons of skill in the art have not been described in detail in order not to obscure unnecessarily the present invention. Various techniques and mechanisms of the present invention will sometimes be described in singular form for clarity. However, it should be noted that some embodiments include multiple iterations of a technique or multiple mechanisms unless noted otherwise. Similarly, various steps of the methods shown and described herein are not necessarily performed in the order indicated, or performed at all in certain embodiments. Accordingly, some implementations of the methods discussed herein may include more or fewer steps than those shown or described. Further, the techniques and mechanisms of the present invention will sometimes describe a connection, relationship or communication between two or more entities. It should be noted that a connection or relationship between entities does not necessarily mean a direct, unimpeded connection, as a variety of other entities or processes may reside or occur between any two entities. Consequently, an indicated connection does not necessarily mean a direct, unimpeded connection unless otherwise noted. 
     The following list of example features corresponds with  FIGS. 1-13  and is provided for ease of reference, where like reference numerals designate corresponding features throughout the specification and figures: 
     
       
         
           
               
               
             
               
                   
               
             
            
               
                 a system for viewing nanoparticles 
                 10 
               
               
                 a light source 
                 15 
               
               
                 electromagnetic energy (beam or sheet) 
                 20 
               
               
                 a cuvette 
                 25 
               
               
                 an alternate embodiment of a cuvette 
                 25A 
               
               
                 a cuvette insert 
                 28 
               
               
                 an alternate embodiment of a cuvette insert 
                 28A 
               
               
                 a third alternative embodiment of a cuvette insert 
                 28B 
               
               
                 a cuvette holder 
                 29 
               
               
                 a sensor 
                 30 
               
               
                 cuvette exterior walls 
                 35 
               
               
                 cuvette floor 
                 40 
               
               
                 cuvette volume 
                 45 
               
               
                 backscatter reflection 
                 47 
               
               
                 transparent portion of cuvette exterior wall 
                 50 
               
               
                 viewing chamber 
                 55 
               
               
                 an upper viewing chamber wall 
                 60 
               
               
                 a lower viewing chamber wall 
                 65 
               
               
                 charged upper and lower viewing chamber wall 
                 67+, 67− 
               
               
                 non-reflective surface of upper and lower 
                 68 
               
               
                 viewing chamber walls 
               
               
                 vertical viewing chamber wall 
                 69 
               
               
                 a reflecting wall 
                 70 
               
               
                 highly-reflective surface of reflecting wall 
                 72 
               
               
                 opening from viewing chamber to backscatter chamber 
                 74 
               
               
                 a backscatter chamber 
                 75 
               
               
                 backscatter chamber walls 
                 77 
               
               
                 retention structure 
                 78 
               
               
                 fluid communication between backscatter chamber 
                 80 
               
               
                 and viewing chamber 
               
               
                 reflection of electromagnetic energy by the reflecting wall 
                 85 
               
               
                 mixing chamber 
                 90 
               
               
                 mixing chamber wall 
                 93 
               
               
                 fluid communication between mixing chamber and 
                 95 
               
               
                 viewing chamber 
               
               
                 mixing stick 
                 100 
               
               
                 lower quality portion of cuvette exterior wall 
                 105 
               
               
                 lifting block 
                 110 
               
               
                 radio tag 
                 120 
               
               
                 electrical isolation break between upper and lower 
                 125 
               
               
                 viewing chamber walls 
               
               
                 spacers 
                 178 
               
               
                   
               
            
           
         
       
     
     The primary objective of the invention is to provide features inside a standard-sized cuvette that prevent or greatly limit liquid flow during recording of videos while still permitting the light sheet to enter the cuvette, and scattered light to exit the cuvette, while also allowing for stirring of the liquid inside the cuvette. The objective has been achieved through two parallel surfaces arranged so they straddle the incoming light sheet and enable recording of scattering light in a perpendicular direction. A second embodiment is to have only one surface that is parallel to the bottom of cuvette, with the base of the cuvette being lifted so the light beam enters between said surface and the bottom of cuvette. In the first embodiment the surface closest to the bottom of the cuvette should have openings to permit stirring of the portion of the liquid between the two parallel surfaces. Additionally, an angled element placed in the path of the light sheet between the field of view of the video camera and the back wall of the cuvette prevents backscattering by reflecting the light sheet upwards and away from the field of view of the camera. 
     The manufacturing of these special-purpose cuvettes can be accomplished in at least two ways. One option is produce inserts (i.e., insert  28  shown in  FIGS. 3-6 ; insert  28 A shown in  FIGS. 7-10 ; insert  28 B shown in  FIGS. 12-13 ) that are placed inside standard commercially-available glass cuvettes. Another option is to have the features molded into a cuvette that may be primarily made from plastic but with two optical glass windows molded into each of two sides of the cuvette 90 degrees apart. Such a construction may reduce costs by minimizing the use of expense materials such has optical grade glass. The following figures will more fully describe the innovation. 
       FIG. 1  illustrates a conventional laboratory setup with a system  10  to observe the Brownian movement of nanoparticles. A light source  15 , generally a laser with associated optics (not shown) produces electromagnetic energy  20  (a light beam or sheet) that enters the cuvette  25 . The cuvette  25  contains a liquid along with the nanoparticles. A sensor  30 , which may include a microscope or camera (not shown), records the image from the cuvette  25 , perpendicular to the direction of the electromagnetic energy  20 . The cuvette  25  is held in place by a holder  29  that prevents movement of the cuvette to reduce motion-induced blurring and produce better images. According to the teachings of the present invention, the cuvette  25  may contain a cuvette insert  28  (shown in  FIGS. 3-6 ) or insert  28 A (shown in  FIGS. 7-10 ) or insert  28 B (shown in  FIGS. 12-13 ), as discussed in detail below. 
       FIG. 2  illustrates the backscatter effect that causes blurry images and volume uncertainty. The electromagnetic energy  20  enters the cuvette  25  and hits the cuvette exterior wall  35 , causing the electromagnetic energy  20  to become less focused and thickened. This backscatter reflection is shown by arrows  47 . When this less-focused light sheet hits the nanoparticles, the images captured by the sensor  30  may become blurred. While processing techniques exists to de-blur the images to some extent, the blurred images can and do lead to inaccurate analysis of Brownian motion. 
       FIG. 3  is an isometric view of a novel insert  28  that may be placed into a conventional cuvette  25  to overcome limitations of the standard design. The electromagnetic energy  20  enters the insert  28  as shown, passing through a viewing chamber  55  bounded by an upper viewing chamber wall  60  and a lower viewing chamber wall  65 , and reflects at an angle off of a reflecting wall  70 , entering a backscatter chamber  75 . The angle may be between 30 and 60 degrees, optimally 45 degrees. The backscatter chamber  75  effectively prevents any backscatter from entering the viewing chamber  55 . The sensor  30  can sense nanoparticles in the viewing chamber  55  in a direction that is perpendicular to the direction of travel of the electromagnetic energy  20 . The reflecting wall  70  is highly reflective and angled so that the impinging electromagnetic energy  20  will be directed away from the viewing chamber  55  and into the backscatter chamber  75 . 
     The insert  28  may also have one or more retention structures  78  in the backscatter chamber walls  77 . The retention structures  78  extend away from the insert  28  and apply pressure to the cuvette to retain the insert  28  in place. These may be simple flaps as shown, or any other form of retention structure or adhesive as will be familiar to one skilled in the art. 
     The insert  28  may also include a mixing chamber wall  93  that elevates the insert  28  away from the bottom of the cuvette and, together with the lower portion of the cuvette, forms a mixing chamber  90 . Fluid communication  95  between the mixing chamber and the viewing chamber and fluid communication  80  between the backscatter chamber  75  and the viewing chamber  55  allow the mixing motion to translate throughout the liquid within the insert  28 . By increasing the thermal homogeneity of the liquid, this mixing motion minimizes thermally generated micro flows that can cause errant movement other than the desired Brownian motion. In an alternate use of the insert, the suspension liquid may fill substantially all of the viewing chamber  55 , but the liquid does not fill the backscatter chamber  75 . In such a use, the backscatter chamber  75  is still in fluid communication with the viewing chamber  55  and can still function to prevent deleterious backscatter of electromagnetic energy within the viewing chamber. 
     A radio tag  120 , such as a radio-frequency identification (RFID) tag, may be attached to the cuvette insert  28  to monitor how many times it is used. RFID uses electromagnetic fields to automatically identify and track tags attached to objects, as is known in the art. The tag  120  contains electronically-stored information which is passed to a nearby reader (not shown) via a radio signal. The tag  120  may include, for example, a moisture sensor that detects the presence of a suspension liquid, such that each time the liquid is changed the sensor would register that change, indicating a separate use of the cuvette/insert. 
       FIG. 4  is a cross-sectional side view of the insert  28  which illustrates the path of the electromagnetic energy  20 . The electromagnetic energy  20  reflects off of the reflecting wall  70  which has a highly reflective surface  72  and is angled away from a vertical viewing chamber wall  69 , and then enters the backscatter chamber  75 , which prevents the electromagnetic energy  20  from then reentering the viewing chamber  55  and causing blurred imagery or volume uncertainty. An arrow  85  shows reflection of electromagnetic energy by the reflection wall. The distance between the upper viewing chamber wall  60  and the lower viewing chamber wall  65  may be on the order of approximately 2 mm or another suitable dimension. 
     To further assist with reducing backscattering, upper and lower viewing chamber walls  60 ,  65  of the insert  28  may be painted black or have another non-reflective surface  68  applied. The sensor  30  would be placed perpendicular to the plane of the paper, and focused on the viewing chamber  55 . Below the viewing chamber  55  and above the cuvette floor  40  is a mixing chamber  90  with a mixing stick  100  that is agitated by a magnet (not shown) outside of the cuvette  25 . 
     The cuvette  25  may further be retained in the holder  29  by one or more spacers  178  in contact with the cuvette exterior walls  35 . 
       FIG. 5  is a top view of the insert  28  inside of the cuvette  25 . The mixing stick  100  is shown as a dashed line because it is below the viewing chamber walls  60 ,  65  of the insert, and cannot be seen from the top view. Fluid communication  80  between the backscatter chamber and the viewing chamber and fluid communication  95  between the mixing chamber and viewing chamber exist so that when the mixing stick  100  is agitated, that mixing motion translates throughout the cuvette volume  45 . A dot  85  indicates reflection of the electromagnetic energy by the reflecting wall. For an exemplary cuvette with an outer dimension of 12.5 mm, a holder 13.3 mm in width would be appropriate, with spacers  178  retaining the cuvette  25  within the holder  29 . 
       FIG. 6  shows that the manufacturing of the insert  28  can be accomplished by cutting, bending and welding or gluing thin sheets of a material such as aluminum. Cutting and bending a sheet according to  FIG. 6  results in the insert shown in  FIG. 3 . The sheet metal is cut as shown. Broken lines indicate bending locations, while spot welds are to be made at the points indicated. Two tab ends are painted as marked to provide the non-reflective surface of the viewing chamber walls  68 . In steps (1) and (2), the opposite-side partially painted tab and its attached smaller tab are bent up 90°. At steps (3), (4), and (5), the partially painted-on-top tab is bent down 90°, its attached smaller tab is bent up 90°, and an adjacent small tab is bent up 90°. In steps (6) and (7), small tabs which will form the reflecting wall  70  are bent up 45°. At steps (8) and (9), the backscatter chamber walls are bent up 90°. Step (10) is to pull the tabs of the retention structure  78  out slightly. Alternatively, or additionally, the cuvette can be chemically bonded to the insert to make an integrated cuvette/insert assembly. 
       FIG. 7  is a cross-sectional side view of an alternate embodiment of a cuvette insert  28 A that may be used. The insert allows the electromagnetic energy  20  to enter and exit the cuvette  25 . The upper viewing chamber wall  60  may be painted black or have another non-reflective surface applied. Unlike the previously disclosed embodiment, the viewing chamber  55  and the mixing chamber  90  are one and the same, and the floor of the cuvette  40  doubles as the lower viewing chamber wall  65 . The insert  28 A may also include a vertical-viewing chamber wall  69  that elevates the insert away from the bottom of the cuvette  25  and creates the viewing/mixing chamber  55 ,  90 . The cuvette  25  may be raised within the holder  29  by a lifting block  110  having dimensions of, for example, 11 mm by 11 mm by 6.25 mm. The cuvette  25  may have a typical thickness of 1.25 mm, and the viewing/mixing chamber  55 ,  90  may be 2 mm in height. The electromagnetic energy  20  would then enter the cuvette  25  at a height of 8.5 mm. 
       FIG. 8  is a top view of the insert  28 A inside of the cuvette  25 . The mixing stick  100  is shown as a dashed line because it is below the upper viewing chamber wall  60 , and cannot be seen from the top view. Fluid communication  80  between the backscatter chamber and the viewing chamber and fluid communication  95  between the mixing chamber and viewing chamber exist so that when the mixing stick  100  is agitated, that mixing motion translates to the cuvette volume  45 . A dot  85  indicates reflection of the electromagnetic energy by the reflecting wall. For an exemplary cuvette with an outer dimension of 12.5 mm, a holder 13.3 mm in width would be appropriate. 
       FIG. 9  is an isometric view of the insert  28 A that may be placed into a conventional cuvette  25 . The insert  28  may also have retention structures  78  that extend away from the insert and apply pressure to the cuvette  25  to retain the insert  28  in place. An opening  74  from the viewing chamber to the backscatter chamber enables fluid communication and passage of electromagnetic energy. A radio tag  120  may be attached to the cuvette insert  28 A for asset-monitoring purposes, as discussed above. 
       FIG. 10  shows that the manufacturing of the insert  28 A can be accomplished by cutting, bending and welding or gluing thin sheets of a material such as aluminum. Cutting and bending a sheet according to  FIG. 10  results in the insert shown in  FIG. 9 . The sheet metal is cut as shown. Broken lines indicate bending locations, while spot welds are to be made at the points indicated. A tab end is painted as marked to provide the non-reflective surface of the viewing chamber walls  68 . In steps (1) and (2), the opposite-side partially painted tab and its attached smaller tab are bent up 90°. At step (3) a small tab which will form the reflecting wall  70  is bent up 45°. At step (4), the backscatter chamber walls are bent up 90°. Step (5) is to pull the tabs of the retention structure  78  out slightly. 
       FIG. 11  shows a novel cuvette  25 A that may be used with the inserts described herein. Cuvettes are generally made of high-quality glass and thus can be extremely expensive. The cuvette  25 A is primarily made of a less expensive plastic. The cuvette exterior wall has a main lower-quality portion  105  with smaller transparent portions  50  where the light sheet enters and the sensor  30  views the nanoparticles. These portions  50  are made of high-quality glass, minimizing backscatter and other optically deleterious effects. When the insert  28 A ( FIGS. 7-10 ) is used, the cuvette  25 A may also include a region that allows the light sheet to exit the cuvette  25 A, minimizing backscatter. A radio tag  120  may be attached to or imbedded in the cuvette  25 A for asset-monitoring purposes, as discussed above. 
     Referring to  FIGS. 12 and 13 , an insert  28 B is disclosed that may be used to determine the zeta-potential of the nanoparticles. The upper and lower viewing chamber walls  60 ,  65  may be electrically charged  67 +,  67 - to create an electromagnetic field within the viewing chamber  55 . The upper viewing-chamber wall  60  is electrically isolated from the lower viewing chamber wall  65  as shown in  FIG. 12  where there is a break in the conduct material between the upper and lower viewing chamber walls  60 , 65  (shown at position  125 ).  FIG. 13  illustrates this construction where the upper viewing chamber wall  60  is in electric conductivity with the portion of the insert  28 C shown as a solid line. Another portion of the insert  28 B is in electrical conductivity with the lower viewing chamber wall  65  (shown as a dashed line), where the break  125  electrically isolates the upper and lower viewing chamber walls  60 , 65  from each other. When electric potential is being applied to two parallel surfaces of the insert  28 B, the presence of an electric field across the colloid forces particles that are forming the colloid to move toward the electrode of opposite charge to the charge that is present on each particle (the so called zeta-potential or layer of charge on the interface between the particle surface and the liquid in which it is immersed). By tracking the speed of movement of each particle versus the applied electric field (when light is being introduced into cuvette, scattered on the particles of the colloid and then recorded by the camera as a time series of images), one can estimate the value of zeta-potential using electrophoresis theory of M. Smoluchowski ( 1903 ) “Contribution à la théorie de l′endosmose électrique et de quelques phénomènes corrélatifs”, Bull. Int. Acad. Sci. Cracovie, 182-199, the contents of which are incorporated herein by reference. The configuration of the electric field perpendicular to the direction of light illumination and perpendicular to the direction of observation allows for easy estimation of the speed of the particles induced by the electric field; the speed is equal to the distance travelled in time divided by that time, and both are easily measurable between two positions of any particle tracked in video recorded during measurement. 
     RESULTS 
     In multiple tests on prototypes and commercial implementations of the cuvette/insert disclosed herein, the following have been shown. First, all backscatter from the cuvette wall opposite from the wall where electromagnetic energy enters the cuvette is eliminated by the angled reflective surface in the viewing chamber—i.e., reflecting wall  70 . By eliminating this backscatter, the volume of the measured sample remains constant, and out-of-focus/blurred image effects that are present in a standard cuvette without the insert are removed. 
     Second, thermally induced flow resulting from localized thermal gradients generated by the electromagnetic energy can be removed in certain regions of the viewing chamber. Mechanically induced flow from stirring is typically arrested in the viewing chamber within 1 or 2 seconds of stopping the stirring. Without the insert (i.e., in a standard cuvette with no insert), mechanically induced flow from stirring is typically present for 10 seconds after the string is stopped. 
       FIGS. 14 and 15  confirm that the insert does arrest bulk liquid flow. Both  FIGS. 14 and 15  are a composite of 300 frames of video showing particles in motion.  FIG. 14 , where no insert was used, illustrates how particles move primarily with the bulk liquid flow in a substantially linear direction that is common to all the particles.  FIG. 15 , where the insert is used, illustrates how bulk liquid flow is eliminated such that the only particle movement is through Brownian motion with no discernable pattern common to all the particles. The conditions and the sample are the same in  FIGS. 14 and 15 —the only change is the inclusion of an insert as disclosed herein. 
     While the systems, methods and structures described herein have made reference to viewing and analyzing nanoparticles, these same systems, methods and structures may be used for larger particle dimensions, such as micron-sized particles. 
     Although exemplary embodiments and applications of the invention have been described herein, including as described above and shown in the included example figures, there is no intention that the invention be limited to these exemplary embodiments and applications or to the manner in which the exemplary embodiments and applications operate or are described herein. Indeed, many variations and modifications to the exemplary embodiments are possible, as would be apparent to a person of ordinary skill in the art. The invention may include any device, structure, method, or functionality, as long as the resulting device, system or method falls within the scope of one of the claims that are allowed by the patent office based on this or any related patent application.