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Sensing systems - Coggle Diagram
Sensing systems
Hydrogels
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polymeric chain structure (probably cross linked) with high water content, up to 99% water
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different preparation methods result in different classifications of hydrogels: homopolymer, copolymer, multipolymer or interpenetrating network (IPN) hydrogels
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Behavior
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increasing number of cross links decreases water content equilibrium,increasing mechanical properties
Native extracellular matrix allows cells to connect between growth binding domains, very biologically complex and bioactive but poor modularity
Natural polymers are naturally cells binding but must have attached growth factors, have average biological complexity, bioactivity and modularity
Synthetic polymers have large numbers of cross links, increasing mechanical properties, cell binding and growth factor domains must be deliberately tied onto the polymer. High modularity but low biological complexity and bioactivity
Polyacrylate Hydrogels
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can absorb 30wt% water, but newer iterations can absorb up to 60wt%
low mechanical properties, can be improved through cross linking
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Detached retina
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injection treatment involves injecting and oxygen permeable viscous vitrous humor replacement which forces the retina down
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artificial retina
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Epiretinal
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head mounted camera, signals to electrode at back of the eye
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Subretinal
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photovoltaic cells convert optical info into electrical stimulation which exites the retina and induces visual perception
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Suprachoroidal
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increases ability to avoid objects, does not fully restore vision
Contact Lenses
first suggested by Da Vinci 1508,the Rene Descartes suggested corneal contact lenses in 1632, finally sir Harold Ridley saw the low inflammatory response of PMMA from shattered spitfire cockpits leading to first intra-ocular lens in 1949
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hard lenses
originally PMMA now rigid permeable co-polymers of MMA with siloxanylalkyal methacrylates or fluorine or silane monomers giving good oxygen transport
silanes as co-polymers: increase O2 permeability (positive), increase biofouling due to high lipidophilicity (negative)
Florination as co-polymers: increases O2 permeability, increases biofouling resistance (both positive)
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Ear
function & structure
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Middle ear bones
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damage to these bones results in deafness, if signal is lost no sound can pass
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Cochlear Implants
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Concerns
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power too high through electrodes,resulting in heating inner ear
connection of external receiver and signal processor becoming loose in the head, leading to risk of infection
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Eyes
Ciliary body responsible for focusing the lens, when relaxed the lens flattens so long distance vision possible, for short distance muscles tense and lens becomes round
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anterior cavity (between lens & cornea) filled with aqueous humor, similar composition to blood plasma
posterior cavity filled with vitreous humor, c. 80% of lens vol, higher viscosity than aqueous humor
retina
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rods-light perception at low light levels, not able to distinguish color
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Glaucoma Treatment
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Drug treatment
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can be in form of eye drops, gives variable dose with time
can use drug releasing contact lens, gives slow release of drug
Valve and stents
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should have limited flow, otherwise insufficient aqueous humor causing other problems
Triblock copolymer, poly(styrene-isobutylenestyrene) or SIBS, used to make drainage conduit (very narrow tube)
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can be brittle, in eye so protected from major damage
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istent (2012), manufactured of Ti coated with heparin, 1x0.3mm
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Hyrdrus microstent, 8mm long nitanol that expands upon implantation placed in canals of schemm. has decreased baseline IOP by 20% in 80% patients after 2yrs
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