Portable Rapid Diagnostics Disease control for developing countries

Project GoalTo build affordable portable rapid diagnostic devices that can successfully aid in disease control

Our project focused on the mechanical side of the device. The molecular technology used for disease detection will be covered, but was not a main component of our research.

Device FunctionA liquid drop of the sample is placed on a slide, and the drop is physically aligned between the emitting LED and the detecting photodiode and fiber optic receiver.

Device purpose and benefit● Rapidly diagnose blood and tissue samples

in the field

● Inexpensive user-friendly device for reliable disease control device

● Alert government of problematic disease areas quickly and before outbreaks

Device Diagram

Key Device Features● Battery powered - easily available 9V power

source in any country● Low power signal - Light Emitting Diode (LED)

emission signal with a fiber optic cable and photodiode to receive the signal after passing through the sample

● Indicator LED - indicator light turns off once sample is properly aligned

● Circuit - Operational amplifiers detect amount of light scattering (positive or negative sample)

Historical BackgroundRapid Diagnostic Tests (RDTs) are the prefered method of testing samples in the field where microscopy or a laboratory may not be practical

RDTs provide a user with a quick reliable way to classify positive and negative samples

Major drawbacks of many RDTs is their high cost

Technical Features● Molecular detection

● Determining sample scattering

● Sample Alignment

Disease detecting antibodies are conjugated with gold nanoparticles

In positive samples, antibodies will cluster around infectious areas.

In negative samples, the antibodies have no preference for a particular site, and the distribution will be uniform.

Molecular Detection

Distinguishing SamplesPositive and Negative samples are distinguished by light scattering from gold nanoparticles

A uniform negative sample will focus light through the drop as expected

A positive sample will have areas of clustered gold nanoparticles, and create a lower signal reading

Sample Alignment

Sample AlignmentFor consistent readings, light must hit the drop a the same angle every time.

To accomplish this, an optical property of curved surfaces is incorporated to ensure proper alignment

Optical caustics aid in the visual alignment

Optical CausticsA caustic is the bright pattern of reflected or refracted light rays on one surface to another

The recognizable shape has been used in many other fields, especially digital image rendering

Application of CausticsA curved surface, in this case a liquid drop, creates a bright area where the signal is most intense

Using operational amplifiers, the reading from the fiber optic reciever is processed and the indicator LED is shut off when the brightest region of the caustic is properly aligned

Consequences of DeviceConsistent readings can be taken using a simple monochromatic LED.

Affordable technology can be used with little training

Rapid results can be generated and regional conclusions can be gathered within a day

Further Work to DoMagnetic stabilizer - sample alignment is critical to the device, there are plans to implement a magnetic coupling to ensure emitter and receptor pieces remain stationary

Rechargeable Power Source - the current 9V source can take rechargeable 9V batteries. We are also looking into adding a photovoltaic cell to aid in the recharging batteries

Application and ImpactAffordable health care is in constant need in order to accelerate growth of developing countries

This device proves especially helpful in south american countries combating the spread of mosquito transferred diseases

Early detection can save a government millions of dollars, as opposed to treating a wide spread epidemic

AcknowledgementsSokolov K, Follen M, Aaron J, Pavlova (2003)Real-time vital optical imaging of precancer using anti-epidermal growth factor receptor antibodies conjugated to gold nanoparticles.

Johannes Kofler (2004)Focusing of Light in Axially Symmetric Systems within the Wave Optics Approximation