Future of medical devices
- provide results cheaper and faster
- individualized diagnosis and therapy with minimal side effects
- aid developing world
- lab-on-a-chip devices (pregnancy test)
Sensor
converts input into a signal (usually voltage) which varies in a predictable and reliable way
Processor
further processes the signal using amplification, noise reduction, or comparison to previous signals
Receiver
presents an interpretable message (usually digital readout)
Ohm’s Law
Voltage=Current*Resistance
V=IR
Current
time rate of change of charge (Amperes A)
Resistance
the opposition to current flow (Ohm’s Wierd O)
Capacitance
the ability to store electrical charge (Farads F)
Series
V=V1+V2+V3
I=I1=I2=I3
R=R1+R2+R3
Parallel
V=V1=V2=V3
I=I1+I2+I3
1/R=1/R1+1/R2+1/R3
Kirchoff’s Current Law
Sum of I=0
Kirchoff’s Voltage Law
Sum of V=0
Thermal Sensors
Thermocouple:
- temperature sensing elements formed by fusing 2 dissimilar metals
- SEEBECK EFFECT: current will flow through the metals when one junction is kept colder than the other
- when the circuit is broken (SEEBECK VOLTAGE) then voltage difference can be measured
Thermister:
- homogeneous composites of dissimilar metals
- commonly used in probe and ear thermometers
Mechanical sensors
- measure force that can compute pressure
- a change in shape corresponds to a change in resistance that is measured by passing current through it
Strain Gauge: measures shape deformations
also used in acoustic transducers in phones/microphones
Electrical sensors
-electrodes are used to measure activity of heart and brain
-membrane of cells has a voltage difference critical to function
Patch clamp: takes a section from the membrane and then cytoplasmic current is tested
Chemical sensors
- measure presence/concentrations of chemicals
Ion selective electrode: detects ions and measure voltage
Amperometric sensor: current is proportional to concentration of molecules generating the current. EX: Clark Electrode (measures oxygen)
Optical sensors
- detect light
- photomultipliers/photodiodes convert the light into an electrical signal
- every time the light hits an electron in a photomultiplier, the electrical signal is multiplied
How infections affect temperature
macrophages at the infection release pyrogens which act on the hypothalamus this releases prostaglandins. This prostaglandins raise the body temp. Hypothalamus causes shivering to increase heat production and vasoconstriction to reduce heat loss
Types of temperature measuring tools
- core body temp: CATHETERS guided to the heart through artery or vein (usually have THERMISTORS)
- ear: IR radiations measured with a PYROELECTRIC CRYSTAL
Electrical stimulation of tissues
- pacemaker to restore rhythm
- cardiac defibrillation restores chaotic rhythm
