Patent Description:
This application claims priority to <CIT>, titled "IMPROVED SPECIAL PURPOSE CUVETTE ASSEMBLY AND METHOD FOR OPTICAL MICROSCOPY OF NANOPARTICLE COLLOIDS", now <CIT>.

This application is related to <CIT>, titled "SPECIAL PURPOSE CUVETTE ASSEMBLY AND METHOD FOR OPTICAL MICROSCOPY OF NANOPARTICLES IN LIQUIDS", now <CIT>, to <CIT>, titled "SPECIAL PURPOSE CUVETTE ASSEMBLY AND METHOD FOR OPTICAL MICROSCOPY OF NANOPARTICLES IN LIQUIDS", now <CIT>, which claimed priority as the non-provisional of <CIT>, titled "SPECIAL PURPOSE CUVETTE ASSEMBLY AND METHOD FOR OPTICAL MICROSCOPY OF NANOPARTICLES IN LIQUIDS", to <CIT>, titled "NANOPARTICLE ANALYZER", now <CIT>, to <CIT>, titled "MULTI-CAMERA APPARATUS FOR OBSERVATION OF MICROSCOPIC MOVEMENTS AND COUNTING OF PARTICLES IN COLLOIDS AND ITS CALIBRATION", now <CIT>, to <CIT>, titled "APPARATUS AND METHOD FOR MEASUREMENT OF GROWTH OR DISSOLUTION KINETICS OF COLLOIDAL PARTICLES", now <CIT>, and to <CIT>, titled "METHOD FOR CALIBRATING INVESTIGATED VOLUME FOR LIGHT SHEET BASED NANOPARTICLE TRACKING AND COUNTING APPARATUS", now <CIT>.

Nanoparticles are ubiquitous, 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 in a broad range of 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 <NUM>-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, <NUM> x <NUM> x <NUM>).

Ideally, there should be no bulk movement of the liquid when the videos are being recorded, so that the only particle motion is pure Brownian motion. However, due to the low thermal conductivity of glass and because of a potentially considerable quantity of energy transmitted from the illuminating beam and absorbed by the liquid and wall of cuvette, one can observe a 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, vibrations of the table on which the instrument is mounted can cause flow, or evaporation of a sample liquid can cool its surface, hence creating temperature gradient that causes flow (convection). Flow can also be induced by stirring the liquid in the cuvette, or by pumping liquids into 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 the 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 the 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 the light sheet that is not fully parallel but rather elliptical), thus creating images that could be partially out of focus for the microscope (fuzzy images), which is 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 affects 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 the 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 driven by an external rotating magnet, or with an external pump.

From the United States patent application publication <CIT> a system is known including the features of the pre-characterizing part of claim <NUM>. Further, a special-purpose cuvette assembly is known from the international patent application publication <CIT>. Further, a cuvette insert is known from the United States patent application publication <CIT>.

What is needed, therefore, is an improved system that can minimize movement of the liquid while also mitigating backscattering-induced broadening of the light within the observation region of the cuvette. These and other objects are achieved by the system according to claim <NUM> and the insert according to claim <NUM>. Advantageous further embodiments are claimed in the dependent claims.

According to a preferred embodiment, a notch or notches may be formed where the first reflecting surface meets the upper viewing chamber wall, the lower viewing chamber wall, or both.

The mixing chamber may include a mixing stick. The mixing chamber may be larger than the viewing chamber.

The upper and lower viewing chamber walls may have a very low-reflective or non-reflective surface. The transparent portion of the exterior walls may be made of a high-quality optical glass. The exterior walls of the cuvette may also include a second portion that is made of a material that is different from the transparent portion.

The cuvette just described may be formed from a separate insert that is constructed to be inserted into a cuvette. The insert may have a mounting structure adapted to facilitate the insert's installation into and removal from the cuvette.

Additional aspects, alternatives and variations, as would be apparent to persons of skill in the art.

The invention is set forth only in the claims and the following summary descriptions of certain examples are not in any way to limit, define or otherwise establish the scope of legal protection.

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.

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 the attached figures and is provided for ease of reference, where like reference numerals designate corresponding features throughout the specification and figures:.

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 permitting scattered light to exit the cuvette at perpendicular direction while also allowing for stirring of the liquid inside the cuvette. The objective has been achieved through two parallel surfaces arranged so that they straddle the incoming light sheet and enable recording of scattering light in a perpendicular direction. Additionally, a mirror is placed in the path of the light sheet between the field of view of the video camera and the back wall of the cuvette so as to (<NUM>) increase the illumination of the particles and (<NUM>) help equalize the thermal gradient so as to mitigate thermal drift of the particles.

The manufacture of these special-purpose cuvettes can be accomplished in at least two ways. One option is to produce inserts 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 has two optical glass windows molded into a side of the cuvette. Such a construction may reduce costs by minimizing the use of expensive materials such as optical grade glass. The following figures will more fully describe the innovation.

<FIG> illustrates a conventional laboratory setup with a system <NUM> to observe the Brownian movement of nanoparticles. A light source <NUM>, generally a laser with associated optics (not shown) produces electromagnetic energy <NUM> (a light beam or light sheet) that enters the cuvette <NUM>. The cuvette <NUM> contains a liquid along with the nanoparticles (colloid). A sensor <NUM>, which may include a microscope or camera (not shown), records the image from the cuvette <NUM>, perpendicular to the direction of the electromagnetic energy <NUM>. The cuvette <NUM> is held in place by a holder <NUM> that prevents movement of the cuvette to reduce motion-induced blurring and to produce better images, allowing temperature measurement and stabilization if needed.

<FIG> illustrates the backscatter effect that may cause blurry images. The electromagnetic energy <NUM> enters the cuvette <NUM> and hits the cuvette exterior wall <NUM>, causing the backscattered electromagnetic energy <NUM> to become less focused and thickened. This backscatter reflection is shown by arrows <NUM>. When this less-focused light sheet hits the nanoparticles, the images captured by the sensor <NUM> 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, also changing the observed volume of colloid. But in close proximity to a reflecting surface (i.e., the minor backscatter broadening region <NUM>), the broadening is not substantial relative to the specifications of the equipment used. In a practical realization of a light sheet generated by a cylindrical lens and an objective, the change of the light sheet around its narrowest point should not be bigger than the depth of field (DOF) of the microscope used to visualize nanoparticles - typically, the narrowest point is about <NUM> microns thick, while at the distance of <NUM> off the center of narrowest point, it is no wider than <NUM> microns, as tested with different diluents (different refractive indices). The DOF of a typical 20x microscope is between <NUM> and <NUM> microns (this is a subjective measurement, as images become more and more fuzzy when one moves off the center of the focus). Therefore, instead of directing the light sheet off the investigated volume, it should be redirected back to illuminate sample again. This can be done by a simple combination of a single <NUM>-degree mirror, or a combination of two mirror surfaces, as shown in <FIG>, where the region observed by the microscope <NUM> is placed near the <NUM>-degree mirror. More mirrors may be used without deviating from the spirit of this disclosure. Moreover, the terms mirror/reflecting surface and reflecting structures are intended to cover mirrors made of glass with metallization on the back, highly polished metal mirrors and other highly reflective surfaces. Optimally, the mirror/reflecting surface or reflecting structure is constructed to reflect at least <NUM>% and, more optimally, at least <NUM>% of incident electromagnetic radiation.

Since the light scattered back by the mirrors illuminates only a slightly wider area than that illuminated by the initial light sheet, one effectively gets a doubling of the light intensity available for the so-called dark background microscopy. What is even more beneficial in the case of slightly light-absorbing particles, is that the two portions of the light sheet have opposite directions, and hence they tend to heat opposite sides of particles, thus mitigating drift due to water expansion near the warm surface of particles.

<FIG> illustrates a viewing chamber <NUM> of the present invention, which may be molded into the construction of a cuvette <NUM> or, alternatively, may be constructed as a cuvette insert <NUM> that fits snugly into a cuvette of standard dimensions, so that electromagnetic energy <NUM> may penetrate a wall <NUM> of the cuvette <NUM> and enter the viewing chamber <NUM>. The viewing chamber <NUM> comprises an upper viewing chamber wall <NUM> that extends from the exterior walls <NUM> of the cuvette <NUM> and a lower viewing chamber wall <NUM> that also extends from the exterior wall of the cuvette <NUM>. Both the upper and lower viewing chamber walls <NUM>, <NUM> are substantially parallel to each other, and the electromagnetic energy <NUM> is directed into the viewing chamber <NUM> in a first direction <NUM> that is parallel to the upper and lower viewing chamber walls <NUM>, <NUM>. The viewing chamber <NUM> is also comprised of a reflecting structure <NUM> that is constructed to reflect the electromagnetic energy <NUM> out of the viewing chamber <NUM> in a second direction <NUM> that is parallel to the upper and lower viewing chamber walls <NUM>, <NUM> but is opposite to the first direction <NUM> from which the electromagnetic energy <NUM> entered. In <FIG>, the reflecting structure is comprised of a first reflecting surface <NUM> that extends from the upper viewing chamber wall <NUM> to the lower viewing chamber wall <NUM> at a <NUM>-degree angle, and a second reflecting surface <NUM> formed in a portion of the lower viewing chamber wall <NUM>. The upper and lower viewing chamber walls <NUM>, <NUM> should have a very low-reflective surface or a non-reflective surface. They may be painted black or coated with a layer of non-reflective material.

Electromagnetic energy <NUM> travels from the exterior walls <NUM> of the cuvette <NUM>, travels into the viewing chamber <NUM> in a direction parallel to the chamber walls <NUM>, <NUM>, strikes the first reflecting surface <NUM>, which may be a mirror, and is angled at <NUM> degrees from the direction <NUM> of the incident energy <NUM>, and the energy <NUM> is thus reflected onto the second reflecting surface <NUM>, which may also be a mirror, that comprises a portion of the lower viewing chamber wall <NUM>. When the energy <NUM> hits the second reflecting surface <NUM>, it is reflected from the second reflecting surface <NUM> to the first reflecting surface <NUM>, which reflects it out of the viewing chamber <NUM> in a direction <NUM> that is parallel to the chamber walls <NUM>, <NUM> but opposite its incident direction <NUM>. Thus, the energy <NUM> enters into the viewing chamber <NUM> and leaves the viewing chamber <NUM> parallel to the chamber walls <NUM>, <NUM>.

<FIG> illustrates one possible embodiment of the reflecting structure <NUM>, the same embodiment shown in <FIG> with a single beam of electromagnetic energy <NUM>. In <FIG> and <FIG>, the second reflecting surface <NUM> is formed into the lower viewing chamber wall <NUM>, making the lower viewing chamber wall <NUM> longer than the upper viewing chamber wall <NUM>. The region <NUM> the sensor <NUM> of the system <NUM> would observe is located away from the corners but also adjacent to the reflecting structure <NUM>, where the electromagnetic energy <NUM> is only traveling parallel to the viewing chamber walls <NUM>, <NUM> with only a minor degree of backscatter broadening.

<FIG> shows an alternative embodiment, where the second reflecting surface <NUM> is formed into the upper viewing chamber wall <NUM>, making the upper viewing chamber wall <NUM> longer than the lower viewing chamber wall <NUM>. The region <NUM> observed by the sensor <NUM> is likewise located away from the corners but adjacent to the reflecting structure <NUM>. In the embodiment shown in <FIG>, the reflecting structure is comprised of a single reflective surface <NUM>, which reflects the light beam <NUM><NUM> degrees (back in the opposite direction), extending orthogonally from the upper viewing chamber wall <NUM> to the lower viewing chamber wall <NUM>. The region <NUM> observed is similarly shown in <FIG>. This configuration can create a backflow of diluent if the scattering surface <NUM> is even slightly absorbing laser light and hence gets warmer in time, thus creating fluid flow by its thermal expansion.

When a ray of electromagnetic energy <NUM> encounters a rounded reflecting surface <NUM>, as shown in <FIG>, and as can be the case when electromagnetic energy <NUM> travels near the corner joining the first reflecting surface <NUM> to a viewing chamber wall, it may scatter in a different direction than parallel to the viewing chamber walls <NUM>, <NUM>, as shown by element <NUM> (stray light beams that do not return into the same volume of observation chamber, thus lowering illumination intensity). The solution to this problem is to use machining to create a notch <NUM> in the viewing chamber wall where the wall surface transitions to the <NUM>-degree reflective surface <NUM>, as shown in <FIG>. With the presence of the notch <NUM>, the incident light <NUM> would be reflected toward the intended direction, as shown by element <NUM>. Although only one notch is illustrated in <FIG>, it would be obvious to one of skill in the art that the notch can be created on one or both surfaces of the viewing chamber walls <NUM>, <NUM>. In other words, the notch or notches <NUM> could be formed where the first reflecting surface <NUM> meets the upper viewing chamber wall <NUM> or where the first reflecting surface <NUM> meets the lower viewing chamber wall <NUM>, or in both the places where the first reflecting surface <NUM> meets the viewing chamber walls <NUM>, <NUM>. This problem of light scattering from a rounded corner may also occur in the embodiment of <FIG>, so a notch or notches may be formed where the reflecting surface <NUM> meets the upper viewing chamber wall <NUM>, the lower viewing chamber wall <NUM>, or both <NUM>, <NUM>.

<FIG> illustrates a specially designed cuvette insert <NUM> that has a mirror slot <NUM>-<NUM> formed at one end of the viewing chamber <NUM>. The insert <NUM> can be manufactured with the mirror slot <NUM>-<NUM> and notches <NUM> formed into the upper and lower viewing chamber walls (<NUM>, <NUM>). An insertable mirror/reflecting surface <NUM>-<NUM> can be separately manufactured and inserted into the mirror slot <NUM>-<NUM>. The insertable mirror/reflecting surface <NUM>-<NUM> could be specially prepared metal mirror (polished) or even a glass one with metallization on the back. This would prevent absorption and would be easy to manufacture.

In all of these embodiments, the sensor <NUM> is positioned to detect the electromagnetic energy <NUM> adjacent to the reflecting structure <NUM> (to the left of the structure). Experimentation has shown that using a visible laser light (wavelengths between <NUM> and <NUM>), this region extends from approximately <NUM> to <NUM> millimeters (see above discussion where broadening of scattered light is described) from the reflecting structure <NUM> for a typical light sheet created by a system of a cylindrical lens f=<NUM> and 4x objective and having <NUM> to <NUM> microns thickness. This distance is measured to the left from the top notch in the direction away from the <NUM>-degree reflecting surface/mirror <NUM> in <FIG>, measured from the bottom notch in the direction away from the <NUM>-degree reflecting surface/mirror <NUM> in <FIG>, and measured away from the orthogonal reflecting surface/mirror <NUM> in <FIG>.

Previously, it was discussed that the viewing chamber <NUM> and the structures inside it may be constructed into a cuvette <NUM>, or into a cuvette insert <NUM> that fits tightly inside a standard cuvette <NUM>. <FIG> illustrate other parts of an embodiment of a cuvette insert <NUM>, but it is to be understood that the features described therein may be formed into the cuvette <NUM> itself instead. In some applications, a cuvette insert <NUM> is versatile and has its advantages.

<FIG> shows the insert <NUM> in an isometric front view, which shows the viewing chamber <NUM> in the front of the isometric top view. This <NUM>-dimensional representation shows an upper viewing chamber wall <NUM>, a lower viewing chamber wall <NUM>, a first reflective surface <NUM> that extends from the upper viewing chamber wall <NUM> to the lower viewing chamber wall <NUM>, two notches <NUM> where the first reflecting surface <NUM> meets the viewing chamber walls <NUM>, <NUM>, and a second reflecting surface <NUM> formed into a portion of the lower viewing chamber wall <NUM>. Also visible in <FIG> are a mounting structure <NUM>, a sample introduction port <NUM>, and an area where fluid communication <NUM> between the mixing chamber <NUM> and the viewing chamber <NUM> occurs. The mounting structure <NUM> is shown as a tab with a hole in the Figures, but may instead comprise a hook or any other structure that allows the insert <NUM> to be easily removed from the cuvette <NUM> to wash it between samples.

<FIG> shows another top isometric view, which offers a better view of the position of the sample introduction port <NUM>, whereby the sample can be introduced into the cuvette insert <NUM> and thus into the cuvette <NUM>.

<FIG> presents a top view of the cuvette insert <NUM>, and <FIG> shows a bottom view. The sample introduction port <NUM> is fluidly communicative with the mixing chamber <NUM>. There is also visible an area of fluid communication <NUM> between the mixing chamber <NUM> and the viewing chamber <NUM>. <FIG> presents the side and cross-sectional views of this portion of the cuvette insert <NUM>. The mixing chamber <NUM> sits below and is separate from the viewing chamber <NUM>. However, there is fluid communication <NUM> between the mixing chamber <NUM> and the viewing chamber <NUM>. The mixing chamber <NUM> may be larger than the viewing chamber <NUM>, and may comprise a mixing stick <NUM>, which may comprise a magnetic stirrer. The shape of the mixing chamber <NUM> and its fluid communication <NUM> to the viewing chamber <NUM> is such that when the mixing stick <NUM> is moving, it does cause eddies or other currents in the viewing chamber <NUM>, thus allowing for different aliquots to be observed (mixing is done between recording of particles movements).

<FIG> presents a front view of the cuvette insert <NUM>, seen through the exterior wall <NUM> of a cuvette <NUM>. <FIG> shows another side view of the cuvette insert <NUM>.

To further assist with reducing backscattering, the upper and lower and back viewing chamber walls <NUM>, <NUM> of the insert <NUM> may be painted black or have another non-reflective surface coating applied <NUM>. The sensor <NUM> would be placed in a position perpendicular to or orthogonal to the plane of the paper and would be focused on the viewing chamber <NUM>. Also, the surfaces of the insert <NUM> that are in the same plane of the sensor <NUM> may be painted black or have another non-reflective coating <NUM> applied.

The cuvette insert <NUM> is for use with a cuvette <NUM> having exterior walls <NUM> and a floor <NUM> that defines a volume <NUM>, where at least a portion of the exterior walls <NUM> is transparent to electromagnetic energy <NUM>, and wherein the volume <NUM> is adapted to contain a suspension of liquid and particles. The insert <NUM> comprises an upper viewing chamber wall <NUM> that extends from the exterior walls <NUM> of the cuvette <NUM> and a lowering viewing chamber wall <NUM> that extends from the exterior walls <NUM>, wherein the upper and lower viewing chamber walls <NUM>, <NUM> are parallel to each other. The electromagnetic energy <NUM> is directed into the viewing chamber <NUM> in a first direction <NUM> that is parallel to the upper and lower viewing chamber walls <NUM>, <NUM>, and a reflecting structure <NUM> in the viewing chamber <NUM> of the insert <NUM> is constructed to reflect the electromagnetic energy <NUM> out of the viewing chamber <NUM> in a second direction <NUM> that is parallel to the upper and lower viewing chamber walls <NUM>, <NUM>, and the first direction <NUM> is opposite to the second direction <NUM>. The insert <NUM> also comprises a mixing chamber <NUM> separated from and in fluid communication <NUM> with the viewing chamber <NUM>, and a sample introduction port <NUM> in fluid communication with the mixing chamber <NUM>.

This insert <NUM> may have its reflecting structure <NUM> comprised of a first reflecting surface <NUM> extending from the upper viewing chamber wall <NUM> to the lower viewing chamber wall <NUM> at a <NUM>-degree angle, and a second reflecting surface <NUM> formed in a portion of the upper view chamber wall <NUM> (<FIG>) or in a portion of the lower viewing chamber wall <NUM> (<FIG>). Further, the insert <NUM> may comprise a notch or notches <NUM> where the first reflecting surface <NUM> meets the upper viewing chamber wall <NUM>, the lower viewing chamber wall <NUM>, or both walls <NUM>, <NUM>, as suggested by <FIG> and <FIG>. Alternatively, the insert's reflecting structure <NUM> inside the viewing chamber may comprise a reflecting surface <NUM> extending orthogonally from the upper viewing chamber wall <NUM> to the lower viewing chamber wall <NUM> (<FIG>, <FIG>). Further, the insert <NUM> may comprise a notch or notches <NUM>, in the embodiment of <FIG>, where the reflecting surface <NUM> meets the upper viewing chamber wall <NUM>, the lower viewing chamber wall <NUM>, or both walls <NUM>, <NUM>. The upper and lower viewing chamber walls <NUM>, <NUM> have a very low-reflective or non-reflective surface <NUM>. The insert <NUM> may further comprise a mounting structure <NUM> adapted to facilitate the insert's installation into and removal from the cuvette <NUM>.

The cuvette insert <NUM> may be used with a mixing stick <NUM> in the mixing chamber <NUM>, as shown in <FIG>. The mixing chamber <NUM> may be larger than the viewing chamber <NUM>. The insert <NUM> may be covered by a thin layer of Teflon or other similar friction-reducing coating <NUM> (see <FIG>) that will allow for light to pass through and yet still seal chemically all of the surfaces of the insert <NUM>, so that one need not worry about colloids that can interact with other materials like proteins and aggregate when in contact with metals.

<FIG> illustrates a cuvette insert <NUM> being inserted into a cuvette <NUM> having cuvette exterior walls <NUM>, a cuvette floor <NUM>, and a cuvette volume <NUM>. The insert moves downward from the top of the cuvette <NUM> towards its floor <NUM>, and displaces some cuvette volume <NUM>. In <FIG>, the insert <NUM> is fully inserted and at rest at the bottom of the cuvette <NUM>. An alternative way to look at this figure is that the structures shown in <FIG> that illustrate the cuvette insert <NUM> have been integrated into a cuvette <NUM>, so that they are a non-separable structure. A portion <NUM> of the cuvette exterior wall <NUM> could be transparent and made of high-quality optical glass, i.e. the portion of the cuvette exterior wall through which the viewing chamber <NUM> of the insert <NUM> would be observed. The second portion <NUM> of the cuvette exterior wall may be made of a material that is different from the material of the transparent portion <NUM>, such as a more cost-effective material.

<FIG> confirm that inserts do work to arrest bulk liquid flow. Both <FIG> are composite images formed of <NUM> frames of video, each of which shows particles in motion. In <FIG>, no insert was used, which illustrates how particles move primarily with the bulk liquid flow in a substantially linear direction that is common to all the particles. In <FIG>, an insert is used, which 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 as between <FIG> - 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.

Claim 1:
A system (<NUM>) for viewing nanoparticles, the system comprising:
a cuvette (<NUM>);
a light source (<NUM>) for generating an electromagnetic energy (<NUM>) directed at the cuvette (<NUM>);
a sensor (<NUM>) for detecting electromagnetic energy (<NUM>) within the cuvette (<NUM>);
wherein the cuvette (<NUM>) comprises:
exterior walls (<NUM>) and a floor (<NUM>) that define a volume (<NUM>), wherein at least a portion of the exterior walls (<NUM>) is transparent to the electromagnetic energy (<NUM>), and wherein the volume (<NUM>) is adapted to contain a suspension fluid and the nanoparticles;
a viewing chamber (<NUM>) comprising:
an upper viewing chamber wall (<NUM>) extending from the exterior walls (<NUM>) and a lower viewing chamber wall (<NUM>) extending from the exterior walls (<NUM>), wherein the upper and lower viewing chamber walls (<NUM>, <NUM>) are substantially parallel to each other;
characterized by
the system being configured such that the electromagnetic energy (<NUM>) is directed into the viewing chamber (<NUM>) in a first direction (<NUM>) that is parallel to the upper and lower viewing chamber walls (<NUM>, <NUM>);
a reflecting structure (<NUM>) constructed to reflect the electromagnetic energy (<NUM>) out of the viewing chamber (<NUM>) in a second direction (<NUM>) that is parallel to the upper and lower viewing chamber walls (<NUM>, <NUM>), wherein the first direction (<NUM>) is opposite to the second direction (<NUM>);
a mixing chamber (<NUM>) separated from and in fluid communication with the viewing chamber (<NUM>); and
a sample introduction port (<NUM>) in fluid communication with the mixing chamber (<NUM>); wherein
the sensor (<NUM>) is positioned to detect electromagnetic energy (<NUM>) in a region adjacent to the reflecting structure (<NUM>);
the detected electromagnetic energy (<NUM>) travels perpendicularly to the first direction (<NUM>); and
the reflecting structure (<NUM>) comprises a first reflecting surface (<NUM>) extending from the upper viewing chamber wall (<NUM>) to the lower viewing chamber wall (<NUM>) at a <NUM>-degree angle and a second reflecting surface (<NUM>) formed in a portion of the upper viewing chamber wall (<NUM>) or in a portion of the lower viewing chamber wall (<NUM>).