GB2537550A - Dynamic light scattering based optical microrheology in non-aqueous solutions - Google Patents

Dynamic light scattering based optical microrheology in non-aqueous solutions Download PDF

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GB2537550A
GB2537550A GB1612133.7A GB201612133A GB2537550A GB 2537550 A GB2537550 A GB 2537550A GB 201612133 A GB201612133 A GB 201612133A GB 2537550 A GB2537550 A GB 2537550A
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particles
hydrophobic
providing
sample
probe particles
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GB201612133D0 (en
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Amin Samiul
Blake Steven
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Malvern Panalytical Ltd
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Malvern Instruments Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N21/49—Scattering, i.e. diffuse reflection within a body or fluid
    • G01N21/51—Scattering, i.e. diffuse reflection within a body or fluid inside a container, e.g. in an ampoule
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N21/49—Scattering, i.e. diffuse reflection within a body or fluid
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
    • G01N2011/0026—Investigating specific flow properties of non-Newtonian fluids
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
    • G01N2011/006—Determining flow properties indirectly by measuring other parameters of the system
    • G01N2011/008—Determining flow properties indirectly by measuring other parameters of the system optical properties
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
    • G01N15/02—Investigating particle size or size distribution
    • G01N15/0205—Investigating particle size or size distribution by optical means
    • G01N15/0211—Investigating a scatter or diffraction pattern
    • G01N2015/0222—Investigating a scatter or diffraction pattern from dynamic light scattering, e.g. photon correlation spectroscopy
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N2021/4704—Angular selective
    • G01N2021/4709—Backscatter

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

A micro-rheological measuring method comprises providing a complex fluid sample 15 that includes a non-aqueous hydrophobic solvent, embedding hydrophobic probe particles 17 in the complex fluid sample, illuminating the sample with coherent light 12, detecting 20 scattered photons from the scattering of the coherent light by the hydrophobic probe particles in the complex sample fluid, performing a correlation operation on a detection signal representative of the detected scattered photons, and deriving at least one theological property of the complex sample fluid from results of the correlation operation.

Description

DYNAMIC LIGHT SCATTERING BASED OPTICAL
MICRORHEOLOGY IN NON-AQUEOUS SOLUTIONS
Field of the Invention
This invention relates to methods and apparatus for obtaining the viscoelastic parameters of non-aqueous complex fluids.
Background of the Invention
Viscoelasticity means the simultaneous existence of viscous and elastic properties in a material. Many complex and structured fluids exhibit viscoelastic characteristics, i.e., they have the ability to both store energy like an elastic solid as well as dissipate energy such as a viscous liquid. When a stress is applied to such a viscoelastic fluid it stores some of the energy input, instead of dissipating all of it as heat, and it may recover part of its deformation when the stress is removed.
The elastic modulus or G' represents storage of elastic energy, while the loss modulus G" represents the viscous dissipation of that energy. The magnitude of G' and G" for most complex fluids depends upon the time scales or frequency at which the property is probed. Depending upon the stress relaxation mechanisms present in the complex fluids, they may exhibit different behaviour (either G'>G" or G">G' or G'=G") at different frequencies. Having the ability to probe the viscoelastic response over a wide frequency range therefore provides insights into the stress-relaxation mechanisms in complex fluids, and since this is connected to the underlying structure of the complex fluid, insights into the underlying structure can be obtained.
Extraction of rheological properties of a fluid through dynamic light scattering (DLS) measurements of the Brownian motion of probe particles has been described in published patent application No. US20130003061, which is entitled DYNAMIC LIGHT SCATTERING BASED MICRORHEOLOGY OF COMPLEX FLUIDS WITH IMPROVED SINGLE-SCATTERING MODE DETECTION and herein incorporated by reference. Essentially the mean squared displacement of the probe particles is obtained from the DLS experiment, from which the theological properties, namely, complex viscosity. elastic modulus, and viscous modulus can be extracted as a function of frequency.
The ability to extract rheological properties in this manner provides a number of significant advantages over traditional rotational mechanical rheometry, namely: * Utilization of small volumes of sample.
* Application of small strains-this is important for strain sensitive materials.
* Access to high frequencies (short times).
In spite of these clear advantages, the applicability of DLS based optical microrheology has been limited to aqueous systems.
Summary of the Invention
Because the applicability of DLS based optical microrheology has been limited to aqueous systems, the adoption of this technology has been limited to only a few clear industrial sectors whilst excluding it from industrial sectors where non-aqueous or hydrophobic (non-polar) solvents are used, such as-oil & gas, lubricants, specialty chemicals etc. The main limitation for utilizing the methodology for hydrophobic solvents has been due to the surface chemistry of the probe particles. Most commercially available probe particles are hydrophilic. Placing then in a hydrophobic environment causes a number of issues such as-aggregation, particle swelling or shrinking, particle chemical breakdown (especially in highly non-polar environments and under harsh pH conditions, among others).
In one general aspect, the invention features a microrheological measuring method that includes providing a complex fluid sample that includes a hydrophobic solvent, embedding hydrophobic probe particles in the complex fluid sample, illuminating the sample with coherent light, detecting scattered photons from the scattering of the coherent light by the hydrophobic probe particles in the complex sample fluid, performing a correlation operation on a detection signal representative of the detected scattered photons, and deriving a least one rheological property of the complex sample fluid from results of the correlation operation.
In preferred embodiments the step of providing hydrophobic probe particles can provide particles with a diameter of between 50 nm and 1.5 microns. The step of detecting can detect backscattering. The step of providing hydrophobic probe particles can provides particle having a surface chemistry that includes aromatic or aliphatic groups. The step of providing hydrophobic probe particles can provide particles having a surface chemistry that includes aromatic or aliphatic groups that are partially unsaturated. The step of providing hydrophobic probe particles can provide particles having a surface chemistry that includes aromatic or aliphatic groups that include linear, branched, and/or cyclic geometries. The step of providing hydrophobic probe particles can provide particles having a surface chemistry that includes aromatic or aliphatic groups that are attached to the probe particles by carbon atoms. The step of providing hydrophobic probe particles can provide particles having a surface chemistry that includes aromatic or aliphatic maps that are attached to the probe particles by heteroatoms. The step of providing hydrophobic probe particles can provide particles having a surface chemistry that includes aromatic or aliphatic groups that are attached to the probe particles by silicon, oxygen, nitrogen, or sulfur. The step of providing hydrophobic probe particles can provide particles having a non-polar surface chemistry. The step of providing can provide hydrophobic particles exhibit sufficient hydrophobicity to effectively disperse with the hydrophobic solvent.
Systems according to the invention can be advantageous in that they can allow for advanced rheoloaical characterization of samples that include non-aqueous solvents. These samples in non-aqueous solutions can be characterized in small amounts, be characterized using small strains, and/or be characterized using high frequencies (short times). They may also be characterized in high-throughput applications.
Brief Description of the Drawing
Fig. 1 is a block diagram of a microrheological fluid characteristic measurement instrument according to the invention; Fig. 2 is a plot of an illustrative con-elation function for the instrument of Fig. ; Fig. 3 is a plot of complex viscosity against angular frequency for a poly (a-olefin) solvent sample measured using the instrument of Fig. I at different temperatures over a temperature range spanning from 20°C to 80°C.
Fig. 4 is a plot of complex viscosity against angular frequency for a mineral oil sample measured using the instrument of Fig. 1 at different temperatures over a temperature range spanning from 50°C to 80°C.
Detailed Description of an Illustrative Embodiment
The invention can be implemented using a variety of rnicrorheological fluid characteristic measurement setups. In one illustrative embodiment shown in Fig. 1, a rnicrorheological fluid characteristic measurement instrument 10 according to the invention includes a coherent light source 12, such as a laser, a sample cell 14 for a non-aqueous sample 15 in which hydrophobic probe particles 17 are suspended.
The hydrophobic probe particles can carry aromatic and aliphatic groups that contain at least one carbon from none to varying degrees of unsaturation and geometries such as linear, branched, cyclic or a combination thereof These groups can be attached to carbon as well as heteroatorns on the surface of the particles such as nitrogen, oxygen, silicon or sulfur. These aspects of the chemistry should be selected to provide sufficient hydrophobicity to effectively disperse with the target hydrophobic solvent.
In this embodiment, the instrument 10 also includes at least one detector 20 and a con-elator 22. The correlator can include autocorrelation logic embodied in hardware and/or software to apply an autocontlation function to a signal from the detector. Single-scattering analysis, such as the viscoelasticity parameter derivations described above, can then be applied to results of the correlation operation to extract one Or more fluid parameter characteristics for the sample. An illustrative correlation function is shown in Fig. 2.
The sample cell 14 can be a short-path-length cell, such as a capillary tube having a diameter of 1.5 mm or less. The use of such short-path-length cells allows the instrument to minimize multiple scattering contributions to the correlation function in the transmission geometry. It is also beneficial in that it allows the instrument to make measurements based on small sample amounts, which is particularly important for biomolecules, such as proteins and small-molecule drugs, for which samples can be particularly small. This can allow the instrument to be used as part of a high-throughput screening system.
The instrument can perform forward-scattering measurements, backscatter measurements, or both. The use of backscatter detection using Non-Invasive Back-Scatter (NIBS) techniques can also help to minimize effect of multiple scattering contributions to the correlation function. This technique involves performing backscattering measurements at close to 1800, (e.g.. 173°), and is described in US patent no. 6016195. German patent 19725211, and Japanese patent no. 2911877, which are herein incorporated by reference. The exact NIBS detector spacing and angles will depend on a variety of factors, including the nature of the sample, the material used for the sample vessel, and the desired accuracy.
The instrument 10 can also include a fibre 16, a splitter 18, such as a 50:50 splitter, and a second detector 20A. The correlator 24 can include cross-correlation logic that allows the instrument to perform a cross-correlation between the signals from the two detectors. This correlation operation allows the instrument to more accurately extract a particle size for samples which are poor scatterers and or are small (a few nrn) in size because the effect of the detector dead time, which determines the shortest autocorrelation time, will be reduced. The cross-correlation operation is also beneficial because it is less sensitive to detector noise issues, such as afterpulsing, which are uncontlated between the detectors. And it can allow the contlator to directly determine the zero time correlation (intercept) of the correlation function, improving the calculation of the high frequency G' and G".
As discussed above, instruments according to the invention can be used as part of different kinds of high-throughput screening systems. Such systems generally include large-scale sample management systems, such as ones that are based on scanning mirrors or robotic X-Y stages. The Malvern Zetasizer APS, for example, provides off-the-shelf automated measurements of samples in industry standard 96-or 384-well plates. To detect bulk properties of the fluids, the sample vessels should have a capacity that is substantially larger than a domain size of the complex sample fluid and is sufficiently large to cause bulk scattering effects to substantially exceed surface effects for the complex fluid sample. Exact sample vessel volumes depend on a variety of factors, including the nature of the sample and desired accuracy levels, Instruments according to the invention can be configured to allow scattered light lobe detected over a range of different angles, such as from 173° to 13.5'. They can also be configured to allow measurements to be carried out in both backscattering mode or transmission mode in order to obtain an extended region of frequency response. These objectives can be accomplished in different ways, such as by allowing a single detector to move or by providing more than one detector. Measurements can also be carried out using a range of different probe sizes ranging from 30 nm to 1 um in order to extend obtained frequency and/or minimize multiple scattering by adjusting a volume of required probe particles. And measurements can be carried out using a range of different probe chemistries to minimize interactions with a complex fluid of interest.
In this example, correlation operations are performed on board the instrument in a dedicated DSP board and single-scattering analyses are performed using specialized software running on a general-purpose workstation. The instrument can also use other approaches to perform these operations, such as dedicated hardware or a combination of software and dedicated hardware.
Example 1
In order to validate the above approach, DLS-based optical microrheology measurements were carried out on the Zetasizer Nano (Malvern Instruments Limited) without any hardware modifications for a poly (a-olefin) solvent sample over a temperature range spanning from 20°C to 80°C. This sample was purchased as a viscosity standard, with known viscosities over the range of temperatures.
The results for the poly (a-olefin) solvent are presented in Fig. 3 and in Table 1.
Temperature (C) Actual Viscosity Measured Viscosity (cP) (cP) 7.79 2.18 4.371 4.01 5.719 4.99 9.174 8.12 10.99 10.07
Table 1
As can be seen from Table 1. the tnicrotheological viscosity measurements track the known viscosity standard properties reasonably well for the poly (a-olefin) solvent sample.
Example 2
In order to further validate the above approach, DLS-based optical microrheology measurements were also can-ied out on the Zetasizer Nano (Malvern Instruments Limited) without any hardware modifications for a mineral oil sample over a temperature range spanning from 50°C to 80°C. This sample was also purchased as a viscosity standard, with known viscosities over the range of temperatures.
The results for the mineral oil are presented in Fig. 4 and in Table 2.
Temperature Actual Viscosity Measured Viscosity (C) (cP) (cP) 10.27 8.26 29.28 22.14 45.89 44.79
Table 2
As can be seen from Table 2, the microrheological viscosity measurements track the known viscosity standard properties reasonably well for the mineral oil solvent sample.
The present invention has now been described in connection with a number of specific embodiments thereof. However, numerous modifications which are contemplated as falling within the scope of the present invention should now be apparent to those skilled in the art. For example, it may be possible to help make the probe particles sufficiently hydrophobic through mechanical surface treatments or other approaches. Therefore, it is intended that the scope of the present invention be limited only by the scope of the claims appended hereto. In addition, the order of presentation of the claims should not be construed to limit the scope of any particular term in the claims.
What is claimed is:

Claims (11)

  1. CLAIMS1. A microrheological measuring method, comprising: providing a complex fluid sample that includes a hydrophobic solvent, embedding hydrophobic probe particles in the complex fluid sample, illuminating the sample with coherent light, detecting scattered photons from the scattering of the coherent light by the hydrophobic probe particles in the complex sample fluid, performing a correlation operation on a detection signal representative of the detected scattered photons, and deriving a least one rheological property of the complex sample fluid from results of the correlation operation.
  2. 2. The method of claim 1 wherein the step of providing hydrophobic probe particles provides particles with a diameter of between 50 nm and 1.5 microns.
  3. 3. The method of claim I wherein the step of detecting scattering detects baascattering.
  4. 4. The method of claim I wherein the step of providing hydrophobic probe particles provides particles having a surface chemistry that includes aromatic or aliphatic groups.
  5. 5. The method of claim 4 wherein the step of providing hydrophobic probe particles provides particles having a surface chemistry that includes aromatic or aliphatic groups that are partially unsaturated.
  6. 6. The method of claim 4 wherein the step of providing hydrophobic probe particles provides particles having a surface chemistry that includes aromatic or aliphatic groups that include linear, branched, and/or cyclic geometries.
  7. 7. The method of claim 4 wherein the step of providing hydrophobic probe particles provides particles having a surface chemistry that includes aromatic or aliphatic groups that are attached to the probe particles by carbon atoms.
  8. 8. The method of claim 4 wherein the step of providing hydrophobic probe particles provides particles having a surface chemistry that includes aromatic or aliphatic groups that are attached to the probe particles by heteroatoms.
  9. 9. The method of claim 8 wherein the step of providing hydrophobic probe particles provides particles having a surface chemistry that includes aromatic or aliphatic groups that are attached to the probe particles by silicon, oxygen, nitrogen, or sulfur.
  10. 10. The method of claim 1 wherein the step of providing hydrophobic probe particles provides particles having a non-polar surface chemistry.
  11. 11. The method of claim 1 wherein the step of providing provides hydrophobic particles exhibit sufficient hydrophobicity to effectively disperse with the hydrophobic solvent.
GB1612133.7A 2015-07-13 2016-07-13 Dynamic light scattering based optical microrheology in non-aqueous solutions Withdrawn GB2537550A (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6958816B1 (en) * 2001-10-05 2005-10-25 Research Foundation Of The University Of Central Florida Microrheology methods and systems using low-coherence dynamic light scattering
WO2011021032A1 (en) * 2009-08-17 2011-02-24 Malvern Instruments Limited Dynamic light scattering based microrheology of complex fluids with improved single-scattering mode detection
WO2015160418A2 (en) * 2014-01-31 2015-10-22 The General Hospital Corporation System and methods for estimation of mechanical properties and size of light-scattering particles in materials

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6958816B1 (en) * 2001-10-05 2005-10-25 Research Foundation Of The University Of Central Florida Microrheology methods and systems using low-coherence dynamic light scattering
WO2011021032A1 (en) * 2009-08-17 2011-02-24 Malvern Instruments Limited Dynamic light scattering based microrheology of complex fluids with improved single-scattering mode detection
WO2015160418A2 (en) * 2014-01-31 2015-10-22 The General Hospital Corporation System and methods for estimation of mechanical properties and size of light-scattering particles in materials

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