Testing the first prototypes of nanoLAMP

We have designed an initial nanoLAMP prototype and stress-tested under the cold of Patagonia. Results: 50% of the subsystems are working!

Introducing the first prototype

The main idea under the first prototyping of the qLAMP was to design a "PCB origami" tube rack that could incubate the reaction tubes at a constant 63ºC and serve as a simple transilluminator to analyze the results right after the amplification.

 

Render of the nanoLAMP 3D model (https://cad.onshape.com/documents/f0e3e657ba1aba259a45a4f3/w/392b09a3f0ab697d9ce48d5e/e/ff6689da0a0ac85146c2cb4b?renderMode=0&uiState=651bed63bc6dac3c3fe09061) 

This prototype is divided into two main submodules: the heating and the transilluminator.

• The heating is done by 8 Surface Mounted (SMD) resistors, responsible for warming up the slots where tubes are positioned (bottom PCB). Each slot is layered with a combination of copper and silver, placed at the reaction height to achieve a temperature ring of 63ºC (The height is calculated assuming 20-25 uL reactions). To ensure even temperature distribution across all 8 tubes we employed an analog circuit, which relies on a comparator and an NTC. Users have the flexibility to adjust the temperature between 53ºC and 70ºC using a discreet potentiometer located at the corner of the device. The device manages the 8 tubes in two distinct segments: the outer 4 tubes and the inner 4 tubes, each one connected to their own analog circuit.

• The transilluminator submodule controls 8 SMD lateral blue LEDs that with a 90º illumination angle, providing side lighting to the reactions. The reaction outcome is measured from below, thanks to a cost-effective Lee filter film placed between two slits, that filters the LED emission light.

A user-friendly switch on the side of the device allows for easy transition between the heating and illumination functions.

 

Diagram of one of the analog temperature control circuits. We used falstad (https://www.falstad.com/circuit/ ) to simulate the circuit. The circuit file can be found in the project temporal repository (https://gitlab.com/open-bioeconomy-lab/diagnostics-hardware/rt-lamp-device/-/blob/master/nanoLAMP/falstad.circuitjs.txt )

From a manufacturing perspective, the entire PCB design is streamlined for cost-effectiveness. The goal is to produce, assemble, and ship each unit at a cost not exceeding $10, with potential reductions to $5 as production volume increases. Upon receipt, the device appears as a singular PCB, which the user can then separate and assemble as a jigsaw puzzle.

In terms of power, the device is designed to be compatible with any 5V source, including power banks and laptop USB ports. However, it's worth noting that its consumption can peak at 1A, so users should be mindful of their power source's capacity.

 

nanoLAMP ready to assemble (left) vs mounted (right)

🔬 Results of the first trial

During our ReGOSH Bahía exploradores residency in Patagonia, we tested both systems independently (Heating and transilluminator) as well as the ability of the device to work under a big range of different power supplies.

Power supply test and portability

✔️ We succesfully tested the system with an external battery, computer USB power, and a standard USB-c phone charger. The consumption reached a peak of 1A @ 5V.

Unfortunately we did not succeed to power it with an smartphone (Using the USB-C port) or some USB-C chargers. For next iterations we would need to try different pull-down resistors on the CC1/CC2 pins of the USB-C.

Heating

❌ The heating system presented the most challenges. Given that the regional Patagonian temperature dropped to 3-4ºC during our tests, the tubes' walls, which were exposed to the external environment, dissipated heat much more rapidly than the heat absorbed around the heating ring, acting as heat dissipators for the reactions. This meant that the reaction temperature inside the tubes was heavily influenced by the volume of the liquid: a greater volume of liquid made more contact with the tube's wall surface, leading to increased heat dissipation.

 

Heat dissipation problems caused by the temperature of the tube walls acting as a heat dissipators.

 

Tubes reached a maximun of 43ºC eventhough the incubation silver ring kept 63ºC

Transilluminator / Reading the reactions ✔️ We conducted tests using various dilutions of Fluorescein isothiocyanate (FITC) to determine the sensitivity of the transilluminator. Our findings indicated that the brightness of a standard positive LAMP reaction, similar in intensity than the most luminous FITC concentration, would be clearly visible.

We identified a design challenge: the LEDs are positioned directly over the reaction liquid due to the current shape of the holes. To ensure optimal visibility, the reaction containers would need a slight elevation to align them correctly with the LEDs. This would need correction during next iterations.

 

Results after trying different serial dilutions of FITC. A positive fluorescent reaction (From LAMP or Cell-Free, is equivalent to the highest FITC concentration (First tube starting from above).