Archive for April, 2014

Contamination Control Technology and Clean Room Equipments

April 29th, 2014

A contaminate is any foreign substance that will have a detrimental effect or deteriorate whatever that one trying to accomplish. Submicroscopic matter/particle is the most significant form of contamination in Clean Rooms that are distributed in the air in the form of fine particles or fibers or carried into the Clean Room and redeposit by workers.

Most significant source of contamination is the operating personnel

  • Hair
  • Skin
  • Dandruff
  • Oral and nasal emissions

This is a partial list of some of the commonly known contaminants that can cause problems in some Clean Room environments. It has been found that many of these contaminants are generated from five basic sources.


  • Walls, floors and ceilings
  • Paint and coatings
  • Construction material (sheet rock, saw dust etc.)
  • Air conditioning debris
  • Room air and vapors
  • spills and leaks


  • Skin flakes and oil
  • Cosmetics and perfume
  • Spittle
  • Clothing debris (lint, fibers etc.)
  • Hair

Tool Generated

  • Friction and wear particles
  • Lubricants and emissions
  • Vibrations
  • Brooms, mops and dusters


  • Particulates floating in air
  • Bacteria, organics and moisture
  • Floor finishes or coatings
  • Cleaning chemicals
  • Plasticizers (outgases)
  • Deionized water

Product generated

  • Silicon chips
  • Quartz flakes
  • Clean room debris
  • Aluminum particles

Contamination control technology

In today’s modern world of manufacturing and research and development, contamination control technology has become necessary part of the manufacturing processes. Contamination control technology is not confined to any one industry. Without contamination control technology, the developing broad field of life sciences encompassing biotech, biomedical, pharmaceutical and drug, microelectronic and aerospace would not have been able to achieve the success and new discoveries.

The primary focus of a Clean Room is to control the levels of contamination by creating a differential pressure between the Clean Room and the surrounding area and to filter the air entering the room to prevent the entry of unwanted particulate matter and to change the air in the room with an air-handling system to purge particulate matter created within the room.

Air showers are self contained chambers installed at entrances to clean rooms and other controlled environments. They minimize particulate matter entering or exiting the clean space. Personnel and material entering the exiting the controlled environment are scrubbed by high velocity HEPA – filtered air jets with velocities of 20-22m/s (4000-4300 fpm).

Contaminated air is then drawn through the base within the unit, filtered and recirculated. Air showers can solve many decontamination problems by offering an effective way of reducing the contaminants carried by individual entering or leaving a controlled area.

The greatest source of particulate contamination in a clean room is the operator/personnel. Air showers are installed between change areas and the clean room. The Air shower enhances clean rooms operating protocol by serving as a reminder to all operators that they are entering a controlled environment. Personnel therefore develop the habit of growing up properly before entering the Air Shower.

Air Shower does reduce particulate and the reduction in particulate matter is dependent upon the particle size, the type of garment worn, the cycle time, and the directly relates to the Air Shower design and how it is used and maintained.

Pass box is used for transferring the materials from and into the Clean Room or the uncontrolled environment to the controlled environment. Controlling the ingress of particulate contamination into Clean Rooms and other controlled environments is paramount in order to maintain the integrity of products and processes.

Personnel traffic is the most important factor which should be controlled. Pass Box allows materials to be transferred into the controlled environment without actual personnel movement. Pass Box may also be used to protect the external environment from egress (the act of coming and going our) of contamination, for example, in biological safety laboratory applications.

Electrical Conductivity-Principle of its Measurement

April 28th, 2014

Electrical Conductivity is a measure of the ability of a substance/solution to conduct an Electric Current (this electric current is carried by ions and the chemical changes that occur in the solution).

Electric Conductivity depends on:

  • Concentration of ions (higher concentration, higher Electrical Conductivity); the determination of the Electrical Conductivity is a rapid and convenient means of estimating the concentration of ions in solution. Since each ion has its own specific ability to conduct current, Electrical Conductivity is only an estimate of the total ion concentration.
  • Temperature of the solution (higher temperature, higher Electrical Conductivity); The Conductivity of a solution is highly temperature dependent, therefore it is important to either use a temperature compensated instrument, or calibrate the instrument at the same temperature as the solution being measured.
  • Specific nature of the ions (higher specific ability and higher valence, higher electric conductivity)

An Electrical Conductivity meter (EC meter) measures the Electrical Conductivity in a solution. Conductivity changes with storage time and temperature.

Principle by which this instrument measures the Electrical Conductivity is very simple; two plates are placed in a sample, a potential is applied across the plates (normally a sine wave voltage), and the current is measured.

Electrical Conductivity is denoted by symbol sigma (σ) and its SI unit is Siemens per metre (S·m−1). Reverse of Electrical Conductivity is known as Electrical Resistivity, which is denoted by symbol rho (ρ).

Electrical conductivity (σ) =             1

Electrical resistivity (ρ)

Relation between potential (V) and current (I) is given by Ohm’s law. According to Ohm’s law current increases with the increase in potential.

i.e.                                V α I

V = RI    (Proportionality constant called Resistance)

R = V/I                                                                                                                                     

Resistance also depends on the temperature; increase in temperature decreases the Resistance.

Compound Microscope-Introduction

April 25th, 2014

A compound microscope uses a very short focal length objective lens to form a greatly enlarged image. In the compound microscope magnification is achieved in two stages. For magnification it utilizes an

  • objective lens ; lens closet to the object; and
  • An eyepiece or ocular lens that one look into it and that is used to further magnify the image formed by the objective lens.

Compound microscopes may have one or two binocular heads for the viewer to examine microscopic organisms, collectively called specimens. The compound microscope also has mechanism to illuminate the specimen for better viewing. The viewing of the specimen is achieved through the interaction of light and the lenses positioned above the specimen. The objective lenses are usually adjustable in order to magnify the specimen. The eyepiece serves as the viewer’s main window into viewing the microscopic organism.

A light source illuminates the object to be seen is an important part of the compound micrscope. That source can be a mirror, or the instrument can be self-illuminating. As light passes through the object, the objective lens nearest the object produces an enlarged image of the object in the primary image angle. The ocular lens o eyepiece acts as a magnifier and produces an enlarged image of the image produced by the objective lens.

Basic parts of a compound microscope

Three basic parts of the compound microscope are head, arm and base.

  • Head; also called the body of the microscope. This part is located at the upper part of the microscope. It is where the optical mechanisms are.
  • Arm; it is located below the head of the microscope. This part serves as the backbone of the compound microscope. It connects the head and the base.
  • Base; The bottom-most part of the microscope, which contains the illuminator.

Optical components of a compound microscope

The optical components of the compound microscope are the following:

  • the eyepiece,
  • the eyepiece tube,
  • the objective lenses,
  • the nosepiece,
  • coarse and fine focus knobs,
  • the stage,
  • the stage clips,
  • the aperture,
  • the illuminator,
  • the condenser,
  • the iris diaphragm and
  • Condenser focus knob.



Figure of a compound microscope showing different parts












Major application areas of compound microscope

  • Hospitals
  • Microbiology
  • Cell biology
  • Research and development
  • Microbiological study
  • Medical diagnostics
  • Medical research