In the past, people trying to swim the depths of the world's oceans have had many limitations. Presently, scuba divers are limited in time and space: in time by the amount of oxygen their tanks can hold, and in space by their bulky gear. Our innovative Aquagill is going to change all that. It is lightweight, sleek in profile, and draws oxygen from the water itself.
First of all, the suit is triple layered. The outer layer will be made of nylon mesh, and is designed to allow water to flow through it. The inner layer is a standard Neoprene wet suit, which is designed for insulating warmth while in the ocean depths. Between the mesh layer and the insulation layer is the osmosis tubing. The tubing is one of the keys to the suit. It is made of a semi-permeable membrane, such as the kind used in kidney dialysis. This membrane will allow oxygen (O2) molecules through it, while keeping other molecules out. Artificial hemoglobin circulating inside the tubing will attract oxygen molecules to itself like natural hemoglobin does in the lungs.
The osmosis tubing covers the entire body suit in a network similar to the blood vessels in the human body. The capillary tubes running around the body are approximately 0.3 mm in diameter, and run parallel to one another. The small tubes converge and flow into larger and larger tubes, like capillaries and main veins in the human circulatory system. The large tubes then go to a pump and on to the oxygen stripper, which is where the oxygen is separated from the hemoglobin. When the hemoglobin comes out of the oxygen stripper it is lean (meaning it has a low oxygen content). It will then branch out to all the tubes, continuing the circuit of oxygen collecting. The stripper removes the oxygen from the hemoglobin and sends the pure O2 to a small, low profile tank made of stainless steel.
Inhaling pure oxygen is very harmful to humans at depths beyond 10 feet due to the partial pressure of the O2. Breathing partial pressures of O2 beyond 1.2 ATM results in uncontrollable seizures, which can lead to drowning when underwater. Our system uses a mix of helium and oxygen, which is known as Heliox. The helium is stored under high pressure in a 1-liter tank.
To gain an understanding of the breathing circuit, we will follow the oxygen from diffusion into the semipermeable tubing to the inhaled breath. Circulating inside the osmosis tubing is artificial hemoglobin. It is in a 0% percent oxygen solution, which creates an affinity for oxygen inside the tubing. Free O2 molecules in the water are drawn in through the tubing by the hemoglobin. A system that can quickly separate the hemoglobin from the oxygen sends the oxygen on to the tank. An O2 sensor measures the percent of O2 in the breathing circuit and opens or closes a control valve off the O2 tank. The O2 sensor receives a signal from a depth sensor, which adjusts the breathing circuit pressure for depth. Also in the breathing circuit is a He sensor. This sensor allows He to enter the circuit from the He tank in the same way O2 is added. The diver then inhales this mixture of He and O2. The exhaled gases of CO2, He, and O2, are pushed by the diverís lungs through a check valve into the CO2 filter, which works just like a rebreather. The filter removes the CO2 and allows the He and O2 to pass on. If external pressure decreases due to a change in depth, a relief valve opens, releasing breathing circuit gases as needed. Should the helium tank lose pressure or run low, a sensor will alert the diver of the condition to allow him or her to rise to the surface.
Flexible membrane tubing is necessary for this design. Brittle, glass semi-permeable membranes are used in chemical industries and by dialysis machines in the year 2001. However, we need tubing that is pliable, allowing the diver to swim around freely.
We estimate that we will need at least 1.6 liters of oxygen to be processed each minute. There is a calculated surface area of six square meters available for tubing that can be fitted on the average diver's suit. The current flow rate in dialysis machines with a six-meter surface area is almost one-and-one-half liters per minute. Using todayís membrane efficiency we will easily be able to get the 1.5-2.0 liters of O2 per minute that we need.
Time and space are two of the main benefits gained from the Aquagill. The two gas tanks and the pump are the only objects that are not found inside the nylon and Neoprene suit. They are all on the diver's back, just like the tank on regular scuba gear. However, these tanks and pump are all quite small, and they leave the diver with much more maneuverability than traditional scuba gear. The only time constraints the diver will have, other than hunger, are the battery and the CO2 filter. The battery will last for at least twelve hours, and for long dives, multiple batteries can be used to stay down longer. CO2 filters work efficiently for approximately 60 hours. If the diver wishes for some reason to stay down longer, he or she only has to take the used CO2 filter off and replace it with a new one.