Membrane Air Separation

Description: 

Membrane air separation experiment, showing air filter and pressure regulator, two Permea membrane modules with valving to permit series or parallel operation, Omega pressure transducer with panel meter, needle valve for flow control, Sierra mass flow meters on tube side (low O2) and shell side (high O2) flows, Engineered Systems oxygen meters on tube and shell side streams.  Air source is a standard cylinder of dry compressed air.

Detailed Overview:

The apparatus consists of two Permea air separation modules, connected by stainless tubing and valves.  Each module contains hundreds of polymeric tubes, the walls of which are more permeable to oxygen than to nitrogen.  Dry air from a standard cylinder passes through a filter to a pressure regulator, which permits setting the operating pressure at which the modules operate.  Air flow through the tube side (fiber lumen side) of the membrane modules can be parallel or series.  Effluent air from tube sides of the modules is combined and passes to a needle valve used to control the total tube side flow rate.  It then flows to a Sierra mass flow meter and an Engineered Systems electrochemical. 

The basic data for each run thus consists of the flow configuration (parallel or series), operating pressure, tube side flow rate and oxygen n level, and shell side flow rate and oxygen level.  A typical run takes about one minute, and consumes little air.  The data can be processed  to produce values for the oxygen and nitrogen permeability coefficients of the module fibers.

The apparatus typically operates at room temperature. 

Diamond-studded electrode: a cure to paralysis

A diamond is forever, not only on your ring, but also inside your body-- implants made from these shiny stones can cure paralysis. Two Case Western Reserve University researchers are building implants made of diamond and flexible polymer that are designed to identify chemical and electrical changes in the brain of patients suffering from neural disease, or to stimulate nerves and restore movement in the paralyzed.

The work of Heidi Martin, a professor of chemical engineering, and Christian Zorman, a professor of electrical engineering and computer science, is years from human trials but their early success has drawn interest worldwide. 

Unlike standard electrodes, diamonds don't corrode. Diamond is so hard and rigid, however, that an entire implant made of the stuff would quickly damage surrounding tissue and the body would seal off the implant as if it were a splinter. The key is to use just enough diamond i. e. just the amount of diamond at the biological interface - where the device connects with a nerve

The real diamond is grown as a film - under high temperature, in a vacuum. By adding impurities  properties of diamond is changed. For electrodes, boron is added, turning the diamond blue. Blue diamonds, including the famous Hope Diamond at the Smithsonian, conduct electricity. Because diamond is made at 800 to 900 degrees celsius, a temperature that would melt the polymer base. Diamond is first selectively grown  in a series of tiny squares of diamond film on silicon dioxide, the stuff of sand and quartz.

Then it is laid in a thin flexible polymer that fills in the gaps between diamonds, followed by a layer of metal that connects to the back of the diamonds and will conduct electricity.
Lastly, he adds a thick layer of flexible polymer base. Then device is dropped in hydrofluoric acid, which eats away the silicon dioxide and frees the probe. 


Small, cortical probes that measure chemical changes at a location in the brain or along a nerve have two diamond contacts affixed. These probes are designed to assist health researchers who are trying to understand the role of chemicals in stimulating nerves or communicating within the brain. Recent research has found, for example, a link between a deficiency in the neurotransmitter dopamine and Parkinson's disease. Lab tests have shown one diamond-coated electrode can monitor chemical and electrical signals as well as stimulate nerves.