BMEN Final

Meshing

For gear to mesh, they must have the same pitch and pressure angle

pitch

Number of teeth per inch of diameter

circular pitch

distance between centers of adjacent teeth

Pressure angle

angle at which teeth meet, measured from perpendicular to line joining centers of two gears

clearance fit

shaft diameter of the fastener is less than the hole diameter of the plate

interference

shaft diameter of fastener is more than the hole diameter of the plate

transition

shaft diameter is such that clearance of interference can exist

Neural Engineering

an emerging interdisciplinary research area that brings to bear neuroscience and engineering methods to analyze neurological function as well as to design solutions to problems associated with neurological limitations and dysfunction

Neuroprosthetics Examples

Chochlear implant, Visual Cortical implant

Example brain stimulation therapies

Vague Nerve stimulation(VNS): used as treatment for epilepsy and more recently for depression in certain case

Deep Brain stimulation(DBS): Used as treatment for Parkinson’s and very recently for depression ad OCD

Nervous System

used to control body’s action, Neurons are electrically excitable cells that process and transmit information using electrical and chemical signals.

Neuron membrane potential

Neurons maintain a voltage gradient across their membranes

Changes in this gradient due to outside stimuli generate an electrochemical pulse called an action potential which carries information to other cells

Hodgkin-Huxley Model for Action Potentials

a mathematical model that descirbes how action potentials in neurons are initiated and propagated

Voltage

water pressure

current

water flow rate

capacitors

store energy electrostatically

Generally composed of two conducting plates separated by dielectric(insulator) material

depends on area, spacing, and dielectric material

Resistor-capacitor circuit

The rate at which a capacitor discharges depends on the time constant of the circuit

Action POtential Mechanism

initiated in response to stimuli that caused sodium channels to open

Sodium/Potassium channels opening and closing cuases charging and sicharging of capacitor giving rise to the characteristic shape of the action potential

Regulation

A rule or directive made and maintained by an authority

US FDA’s medical device regulations

cover manufacture(and importing) by restricting sale and marketing

Class I

simple and present a low risk of harm to the user

subject to “general controls” that are sufficient to protect the user

Examples of Class I

non-powered breast pumps, elastic bandages, tongue depressors, examination gloves, most hearing aids, arm slings, microbial analyzers, keratoscopes

Class II

More complicated with a higher risk of harm to the user

require general and special controls

premarket notification \[510(k)\]

examples of class II

Powered wheelchairs, CT scanner, contact lens care porducts, endolymphatic shunts, orthopedic implants, dental implants

Class II

Most complex, highest risk of harm to the user

Usually sistain or support life, are implanted, or present potenial unreasonable risk of illness or injury

Have the toughest regulatory controls

Must be able to reasonably assure their safety and effectiveness-difficult because more risky

Require premarket approval through a PMA

Examples of Class III

Pacemakers, implanted weight loss devices, non-invasive glucose testing devices, medical imaging analyzers, cochlear implants, breast implants

State of Equipoise

do not truly know which treatment is better necessary to even start a trial

type

observational or interventional. Inteventional is used in safety/efficacy studies

Allocation

Randomized common into arms

Arms

type of intervention (device A, device B, sham, etc)

Masking

single blind, double blind, or open label

Phase 0

exploratory study involving very limited human exposure to the drug, with no therapeutic or diagnostic goals

Phase 1

studies that are usually conducted with healthy volunteers and that emphasize safety. the goal is to find out what the drug’s most frequent and serious adverse events are and, often how the drug is metabolized and excreted.

phase 2

Studies that gather preminiary data on effectivenss (whether the drug works in people who have a certain disease or condition)

phase 3

Studies that gather mor information about safety and effectiveness by studying different populations and different dosages and by using the drug in combination with other drugs

phase 4

studies occuring after FDA has approved a drug for marketing. These including postmarket requirement and commitment studies that are required of or agreed to by the study sponsor. These studies gather additional information about a drug’s safety, efficacy, or optiaml use.

Empirical models

are based on observations or measurements of the systm itself. They are usually limited to characterizing only one specific type of system

Theoretical models

based on physical theory and while widely applicable require that certain assumptions be made

theoretical vs. empirical models

Ideal Model→Design(or redesign) system→ Prototype and Measurements→Refined model→Design System

Types of Biomaterials

Biomaterials→\[Polymers, Metals, Ceramics, Natural\]→Composites

Examples of Polymeric Biomaterials

Polyethylene, Hard Contact lenses, Pacemaker

Metal Biomaterials

Foreign body reaction, Stress shielding, Biocompatibility, Bioactivity, Osteoinduction

Metal Biomaterials examples

Screws in body, Ti alloy single teeth replacement, Kneww replacement, Metal electrodes

Ceramic biomaterials

Bone bonds well to them, exhibit minimum foreign body reaction, high stiffness, low friction and wear coefficients, low fracture toughness, low impact resistance

Examples of ceramic biomaterials

Alumina Femoral head and acetabular liner, zirconia dental crown and birdges, zirconia artificial tooth root

Natural Biomaterials

good biocompatibility and biodegradability, commercial availability, easy processing, closely mimic the natural extracellular matrix of tissues

lot-to-lot variability, cross-contamination, some have poor mechanical properties

examples of natural biomaterials

bioprosthetic heart valve fabricated from a pig’s valve, apligraf skin graft uses collagen as a scaffold for living cells, silk sutures for wound closure

Biocompatibility

noncarcinogenic, nonpyrogenic, nontoxic, nonallergenic, blood compatible, non-inflammatory

Sterilizability

not destroyed by typical sterilizing techniques such as autoclaving, dry heat, radiation, ethylene oxide

physical characteristics of biomaterials

strength, elasticity, durability

manufacturability of biomaterials

machinable, moldable, extrudable

crystallinity

defree of structural order

grain size

finer grain typically stronger than course grain materials

glass transition temperature

reversible transition in amorphous materials from a hard and relatively brittle state into a molten or rubber-like state

melting temperature

temperature at which it changes state from solid to liquid at atmospheric pressure

tensil modulus

fracture, elasticity

electron microscopy

AFM, SEM, SAM

surgace characterization

wettability, roughness, surface mobility

Diode

\

Capacitor

inductor

resistor

DC voltage source

AC voltage source

switch

ground

transistors

operational amplifier

Ohm’s law

V = IR

* V is voltage (volts)
* I is current (amps)
* R is resistance (ohms)

pathway of a signal

Input→transducer→signal→transducer→output

electrical biosignals

time varying signals

electrocardiogram

electrical activity of the heart

electromydogram

electrical activity of the muscles

electroencephalogram

electrical activity of the brain

elextrooculogram

electrical activity of the eye

Galvanic skin response

electrical conductance of the skin

high-pass filter

low-pass filter

band-pass filter

notch filter (band stop)

discrete vs continuous

* continuous signals such as voltage are defined for all instants of time
* discrete signals are defined only at specific times
* \

Manufacturing

physically producing the device

packaging

ensuring that device will get to point of use in apropriate state

sterilization

making devices safe/clean to use

Tissue engineering process

* Biomaterial → Engineered tissue
* Cells → Engineered tissue
* Growth factors/bioreactor→engineered tissue

scaffold

structure the cells grow on

Parenchymal cells

occupy most of the tissue volume, and express functions definitive for the tissue

stromal/mesenchymal cells

connective tissue type about 30% of the cellularity in tissues

subtractive manufactoring

wood carving, drilling holes, lathing, or milling

additive manufacturing

adding things together stacking blocks or building a brick wall, icing a cake

FDM (fused deposition modeling)

molten plastic is extruded along paths in x-y plane, with the z height gradually adjusted so that an object is built up layer by layer -plastic cools and hardens in place

polyjet

sprays polymer out of a print head, cured by UV light, creating layer by layer as z height is gradually adjusted

sensor

a device that detects or measures a physical property and records, indicates, or otherwise responds to it

assay

an investigative procedure for qualitatively assessing or quantitatively measuring the presence, amount or functional activity of a target entity (the analyte)

Bioelectric

electroencephalograph (EEG sensor)

bioimpedance

galvanic skin response (GSR sensor)

bioacoustics

ultrasound (piezoelectric crystal)

biomagnetic

MRI

biomechanical

respiration monitor belt

biochemical

blood glucose monitor b