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Updated 07/10/2024
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Improvement of Polystyrene Nano-Spheres Density and Uniformity of Mechanical Organization on PDMS Substrates Lotem Kitaroo and Sharon Luzky

Effective Brainstorming #

The system being analyzed in the solution is focused on the mechanical organization and distribution of polystyrene nanospheres with varying sizes on a polydimethylsiloxane (PDMS) substrate using a mechanical rubbing process. 

The main components and processes of the system include:


1. Polystyrene Nanospheres-

Materials: Polystyrene nanospheres with specific diameters (e.g., 0.35 µm and 0.5 µm).

Preparation: The nanospheres are prepared in dry powder form by mixing solutions of different sizes, centrifuging to remove liquid, and drying the resultant powder.


2. Polydimethylsiloxane (PDMS) Substrate-

Materials: Silicone elastomer base mixed with a cross-linker.

Preparation: The mixture is degassed under vacuum and cured at 60°C to form a solid elastomeric material. PDMS pieces are cut to fit into the rubbing machine and to match the size of the model holders.


3. Rubbing Process-

Polystyrene powder is sprinkled onto the PDMS substrate.

Smaller PDMS circles (1” diameter) are attached to the model holders, and a larger PDMS piece (8” diameter) is placed on the stage of the rubbing machine.

The rubbing machine operates at 30 RPM, with experiments conducted for different durations (e.g., 6 minutes and 25 minutes).

The machine combines rotational and translational motion to ensure uniform rubbing and avoid the formation of a second layer.


4. SEM Imaging-

Samples are placed in the SEM chamber.

High-resolution images are captured to assess nanosphere distribution, arrangement, and uniformity.


5. Image Analysis using OpenCV-

Detects circular features representing nanospheres.

Differentiates between large and small nanospheres based on radii.

Identifies clusters and calculates statistical metrics such as cluster size and distribution patterns.

ImplementationEasyValidationEasy
Custom Substrates: Preparing substrates using materials like polydimethylsiloxane (PDMS) provides a stable platform with suitable surface properties that facilitate uniform rubbing and distribution of nanospheres. The curing conditions and surface energy of the PDMS can be tailored to improve nanosphere alignment and reduce defects.
Jun 23 2024 2:44:34 pm
Optimizing Rubbing Duration: Experimentation with different rubbing durations (e.g., 6 minutes vs. 25 minutes) has shown variations in the clustering and distribution of nanospheres. Shorter rubbing times tend to form smaller, more stable clusters with less variation, while longer rubbing times can increase cluster sizes and uniformity. This indicates that optimizing the rubbing duration can help control the size distribution and uniformity of the nanosphere patterns.
Jun 23 2024 2:44:03 pm
ImplementationEasyValidationNot Easy
Mixing Nanospheres with Different Sizes: Mixing nanospheres of different sizes before the rubbing process can improve packing density and reduce irregularities. Smaller nanospheres can fill the interstitial spaces between larger ones, leading to a denser and more uniform arrangement.
2
Jun 23 2024 2:45:39 pm
Mechanical Rubbing Process - The unidirectional rubbing technique is used to align and distribute nanospheres uniformly. This method involves controlled friction where nanospheres are rubbed between two surfaces, leading to their alignment and assembly in a specific pattern. Adjusting parameters such as rubbing speed, time, pressure, and substrate surface energy can help achieve a more uniform distribution.
0
Jun 23 2024 2:43:10 pm
ImplementationNot EasyValidationEasy
Statistical Analysis - Utilizing Scanning Electron Microscopy (SEM) for high-resolution imaging facilitates the analysis of the spatial arrangement and packing behavior of nanospheres of varying sizes. By employing image analysis algorithms, such as those in OpenCV, it is possible to detect, measure, and cluster nanospheres based on their sizes, enabling a detailed understanding of their distribution patterns. Additionally, other image analysis algorithms should be employed on the same results to allow for comparative analysis
Jun 23 2024 2:43:35 pm
ImplementationNot EasyValidationNot Easy
Deposition Methods - Given the challenges observed with achieving dense and uniform packing of polystyrene nanospheres using sputtering, it is worth considering alternative deposition methods such as Thermal Evaporation or Vapor Phase Transport (VPT).
Jun 24 2024 3:26:09 pm
Sputtering Conditions - Adjusting the sputtering parameters (e.g., duration, pressure, and material deposition rate) to optimize the density of nanosphere coverage.
Jun 24 2024 2:27:32 pm
Jun 23 2024 2:29:27 pm
Process Functional Modeling #

Process Overview-

  • Objective: Achieve a dense and uniform layer of polystyrene nanospheres on PDMS substrates.
  • Steps: Mechanical rubbing of PDMS, sputtering with nanospheres, SEM imaging, and image analysis.

Problem Statement-

Despite systematic processing, SEM images show sparse and uneven distribution of nanospheres.

Mechanical Rubbing of PDMS

7.8
2.17
OE 3.6

Sputtering with Polystyrene Nanospheres.

5.45
2.18
OE 2.5

SEM Imaging of Samples and Image Processing and Analysis

3.33
3.33
OE 1
Productive operations effectiveness

Effective

Ineffective

Operation types breakdown

Productive

Providing

Corrective

Metrology

Operation TypeDoes it increase cost?Does it increase product value?Recommendation
Productive
YesYesImprove
Providing
YesNoEliminate
Corrective
YesNoEliminate
Metrology
YesNoEliminate
OperationTypeMeritRecommendation
Mechanical Rubbing of PDMS
Productive
OE 3.6
Consider improving
Sputtering with Polystyrene Nanospheres.
Providing
OE 2.5
Consider eliminating
SEM Imaging of Samples and Image Processing and Analysis
Metrology
OE 1
Consider the necessity of the information and eliminate it when possible
Jun 25 2024 3:48:16 pm
Mechanical Rubbing of PDMS #
(by Process Functional Modeling)

Improve the surface preparation of PDMS to achieve a dense and uniform layer of polystyrene nanospheres.

Operational Effectiveness – OE

Effective

Ineffective

OE 3.6
Operational Perfectness - OP

Basic functions

Components

Supersystems

OP 0.4
Functional rank
Problematic rank
Big nanospheres
10
1.5
Small nanospheres
10
1.5
rubbing tool
6.7
Sample holder
6.7
PDMS substrate
6.7
Gear
6.7
10

To reduce the influence of the supersystem and of harmful relationships and to maximize the influence of contributing relationships.

Jun 25 2024 3:52:44 pm
Sputtering with Polystyrene Nanospheres. #
(by Process Functional Modeling)

The system aims to achieve a uniformly coated PDMS substrate with polystyrene nanospheres through a sputtering process. This process involves several components and subsystems that work together to deposit nanospheres onto the PDMS substrate uniformly. The primary product of this system is a PDMS substrate that is densely and uniformly coated with polystyrene nanospheres, suitable for applications in nanoelectronics, biomedical devices, and surface coatings.

Operational Effectiveness – OE

Effective

Ineffective

OE 2.5
Operational Perfectness - OP

Basic functions

Components

Supersystems

OP 0.09
Functional rank
Problematic rank
PDMS Substrate
10
Polystyrene Nanospheres
10
10
Substrate Holder
6
Target Material Holder
6
Sputtering Equipment
6
6
Rotating Mechanism
4
4
Power Supply
4
Control System
4
Cooling System
4
Vacuum Chamber
4
4
Environmental Conditions
2

Ensure maintenance, electrical system and correct parameters in the sputtering system.

Jun 25 2024 3:53:50 pm
SEM Imaging of Samples and Image Processing and Analysis #
(by Process Functional Modeling)

SEM Imaging of Samples. - The system involves imaging polystyrene nanospheres deposited on PDMS substrates using SEM.

Operational Effectiveness – OE

Effective

Ineffective

OE 1
Operational Perfectness - OP

Basic functions

Components

Supersystems

Functional rank
Problematic rank
image processing software
10
10
Algorithms
5
Hardware
5
operator
10
SEM device
No impact
PDMS samples with nanospheres
No impact

Calibration: Regular calibration of the SEM Device.

Training: Enhanced training for operators.

Software Updates: Regular updates and testing of Image Processing Software.

Environmental Control: Maintain optimal room conditions for SEM imaging.

Jun 25 2024 3:54:45 pm
Component: Gear #
Contradiction:
If
Gear remains unchanged
Then
Gear Moves Big and small nanospheres and make them connect
But
Gear Separates Big and small nanospheres
Improving parameter
Description of what is improving:
Gear make particles to connect
Selected improving parameter:
Stress, pressure
Worsening parameter
Description of what is worsening:
Gear also separates particles
Selected worsening parameter:
Volume of moving object
Matching principles:
  • 6
    Universality
  • 10
    Preliminary action
  • 35
    Parameter changes
  • Jun 27 2024 5:12:58 pm
    5 Whys #
    Causes Chain
    Root Cause Analysis

    SEM images reveal that the nanospheres are sparsely distributed with noticeable gaps between them.

    Why?

    Explore alternative deposition techniques such as drop-casting or inkjet printing to achieve a more uniform arrangement of the nanospheres on the substrate.

    3

    Sputtering method being used may not be suitable for achieving dense packing of polystyrene nanospheres.

    Why?

    Investigate and implement a different sputtering method that is known to be more effective for achieving dense packing of polystyrene nanospheres.

    2

    sputtering can cause issues like non-uniform distribution and potential shrinkage of the nanospheres.

    Why?

    Utilize a different deposition technique, such as spin coating, to achieve a more consistent and even layer of nanospheres.

    1

    The energy and dynamics involved in the sputtering process may not be appropriate for depositing delicate materials like polystyrene nanospheres, leading to uneven deposition and structural changes.

    Why?

    Implement a pre-treatment step for the substrate to enhance adhesion and uniformity of deposition.

    0

    Insufficient research or testing on the compatibility of sputtering process with polystyrene nanospheres

    This is the fundamental reason for the problem (FRP).

    Conduct thorough research and testing specifically focused on the compatibility of sputtering process with polystyrene nanospheres

    4
    Jul 6 2024 1:59:12 pm
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    Anatoly Agulyansky avatar

    Anatoly Agulyansky

    07/9/2024

    It is a great job, guys. You analyzed the problem. used creative thinking tools, generated innovative ideas and tested them.

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