Point-of-care diagnostics for low-resource clinics.
MediScan screens a urine sample for multiple diseases without a central lab. I led the electromechanical design across its NAAT, fluorescence and power modules.
What
MediScan: a portable, non-invasive platform that screens a urine sample for multiple diseases at the point of care.
Why
Nearly 47% of the world lacks access to essential diagnostics (WHO, 2021), so diseases are caught late.
How
- NAAT held at 65°C by an ESP32 PI loop: boost converter, MOSFET PWM, thermistor, thermal fuse
- Four blue-LED and photodiode channels reading fluorescence in reflection
- Solar and USB-C charged power board shared by the NAAT and fluorescence modules
Results
- $3.08 per test, $57.22 per NAAT device
- 9.1% of the battery per 20-minute reading
- Boards finalized and sent for fabrication
Inside the NAAT module
A control board, a sensing board, the microfluidic chip and a heating plate. NAAT amplifies genetic material at a constant 65°C, so it needs no PCR hardware.
An ESP32 runs the heater loop and the optics. USB-C and a solar cell charge a 5000 mAh LiPo; a 2.4" display and buttons run the test.
A boost converter lifts the 3.3V rail to 5V for the heater, switched low-side by a MOSFET under PWM. A soldered thermal fuse cuts power on runaway.
Underneath, each channel pairs a blue LED with a Vishay TEMD6200 photodiode, both facing the chip. Detection works in reflection.
The sample sits in a clear PMMA chip, backed by a black PMMA layer, directly under the optical channels.
In direct contact with the chip through thermal grease. A thermistor at the heater feeds a PI loop on the ESP32, with D added only if needed.
Loading CAD model
Board models from the team's Altium CAD. Chip, heating plate and the stacked layout are simplified.
The sensing stack
Blue light excites the amplified sample in each well; it fluoresces green, and the photodiode beside the LED reads it. A channel is positive when its signal crosses the threshold. The RNase P control must amplify too, or the run is invalid.
Illustrative model. Curve shapes, times and which channel reads which target are not measured data.
Power for the field
Worst-case draw is 4.45 W with the heater running. A 20-minute reading uses 1.69 Wh, 9.1% of the 5000 mAh battery, so about ten readings per charge. The solar cell refills it in roughly 37 hours.
Built to be cheap
$57.22 per NAAT device and $3.08 per test, prototyped with free campus fabrication and free or discounted reagent samples.
Three modules, one platform
NAAT for Zika, dengue and malaria. A fluorescence module with two AS7341 spectral sensors for HE4, LYVE-1, PSA, KIM-1 and NGAL. A separate power board shared by both.
Toward the clinic
Mapped the regulatory path: a Class II in vitro diagnostic on the 510(k) pathway, under 21 CFR 820 design controls, ISO 13485 and ISO 14971.