Lab-on-a-Drone: Toward Pinpoint Deployment of Smartphone-Enabled Nucleic Acid-Based Diagnostics for Mobile Health Care

Abstract

We introduce a portable biochemical analysis platform for rapid field deployment of nucleic acid-based diagnostics using consumer-class quadcopter drones. This approach exploits the ability to isothermally perform the polymerase chain reaction (PCR) with a single heater, enabling the system to be operated using standard 5 V USB sources that power mobile devices (via battery, solar, or hand crank action). Time-resolved fluorescence detection and quantification is achieved using a smartphone camera and integrated image analysis app. Standard sample preparation is enabled by leveraging the drone's motors as centrifuges via 3D printed snap-on attachments. These advancements make it possible to build a complete DNA/RNA analysis system at a cost of ∼$50 ($US). Our instrument is rugged and versatile, enabling pinpoint deployment of sophisticated diagnostics to distributed field sites. This capability is demonstrated by successful in-flight replication of Staphylococcus aureus and λ-phage DNA targets in under 20 min. The ability to perform rapid in-flight assays with smartphone connectivity eliminates delays between sample collection and analysis so that test results can be delivered in minutes, suggesting new possibilities for drone-based systems to function in broader and more sophisticated roles beyond cargo transport and imaging.

Figure 1

Lab-on-a-drone. (A) Convective thermocycling enables the PCR to be actuated isothermally using a single heater. (B) The instrument can be assembled for ∼$50 ($US) using readily available components. (C) Fluorescence detection of reaction products is achieved using an ordinary smartphone camera. (D) The entire assembly is incredibly lightweight, enabling deployment on consumer-class quadcopter drones. (E) Ruggedization is demonstrated by performing in-flight PCR as a drone payload. Successful in-flight replication of two different DNA targets is achieved (lane M, FlashGel DNA marker; lane 1, 147 bp S. aureus target (16 min in-flight reaction time); lane 2, 237 bp target from a λ-phage DNA template (18 min in-flight reaction time)). T_amb ∼ 23 °C.

Figure 2

Quantitative smartphone-based fluorescence detection. (A) The PCR to Go analysis app enables smartphone-based image acquisition, processing, and data analysis. (B–D) Measured fluorescence as a function of initial template copy number (237 bp target from a λ-phage DNA template; images acquired by the smartphone camera are shown at the top of each plot). The data in (B) also show that comparable results are obtained when analysis is performed in-flight as a drone payload. (E) Quantification is achieved by applying sigmoidal fits to these data (mean ± sd of 3 replicates) and using reaction times when fluorescence exceeds a threshold value of 20 units to construct a standard curve (inset, C_T = 9.4, 11.8, and 13.3 min for [DNA]₀ = 10⁵, 10⁴, and 10³ copies/μL, respectively), whose slope yields a doubling time of 35.8 s. (F) Convective thermocycling (25 min reaction time) achieves sensitivity in the 10¹ to 10² copy/μL range (lane M, FlashGel DNA marker, remaining lanes correspond to initial DNA copy numbers indicated on the gel image). (G) Smartphone-based fluorescence analysis yields quantification comparable to a benchtop real time PCR instrument, with nearly identical standard curves.

Figure 3

A versatile and rugged PCR analysis platform. (A) Convective thermocycling enables replication of a 150 bp Ebola target (lane 1) and a 147 bp S. aureus target (lanes 2, 3) in 20 min (lane M, FlashGel DNA marker) using USB battery and hand crank power sources. (B) Comparable heater performance is achieved via on- or off-grid electrical power sources. Experiments (C) and reaction model simulations (D) display consistent performance over a broad ambient temperature range. Experiments (E) and simulations (F) show that product yields are insensitive to the reactor’s orientation with respect to the vertical direction up to tilt angles of at least 60°. (G) Simulations verify that favorable flow fields are maintained at these orientations (V and T denote velocity magnitude and temperature profiles). Gels in (C) and (E) show replication of a 237 bp target from a λ-phage DNA template in 25 min (lane M, FlashGel DNA marker; some smearing in the product bands is evident because a hot start enzyme protocol was not employed in these tests). Plots in (D) and (F) show doubling time (above) and fractional reactor volume maintained at each PCR temperature condition (below).

Figure 4

Drone-based sample preparation. (A) The quadcopter blades are replaced with 3D printed rotor attachments to enable standard centrifuge-based workflows. (B) These attachments transform the quadcopter into a centrifuge capable of rotation speeds ω up to 10 000 rpm (below, mean ± sd of three replicates, error bars smaller than the plotted symbols), yielding performance comparable to benchtop instruments (above). (C–E) Images depicting samples before (left) and after (right) drone-based centrifugation. (C) Colored buffer enables visualization of elution through a standard spin column kit centrifuged for 2 min at 10 000 rpm. (D) A 350 nm magnetic nanoparticle suspension centrifuged for 5 min at 10 000 rpm. (E) A 40 nm gold colloid suspension centrifuged for 10 min at 10 000 rpm. (F) Real-time PCR plot of Dengue virus serotype 3 amplification using templates extracted by drone-based and benchtop centrifuges. The quantity of RNA extracted in both platforms is comparable, as evident by quantification cycle (C_q) values of 31.8 and 31.6 obtained using the drone-based platform (two replicates) whereas C_q = 32.5 was obtained when the protocol was performed using a benchtop centrifuge.