Sunlight powered smartphone-assisted medical diagnostics

The Polymerase Chain Reaction is a molecular diagnostic modality used to amplify DNA samples to detectable levels allowing for the recognition of specific DNA sequences characteristic of certain medical conditions. The test is highly sensitive and specific which makes it an indispensable medical diagnostic tool.

The process, however, is energy consuming making the use of such technology very limited in remote areas with limited facilities and undependable electrical source. This challenge is illustrated by the difficulty of on the spot diagnosis for Kaposi Sarcoma, a cancer caused by a virus (HHV-8), and is associated with AIDS. This skin cancer may be indistinguishable clinically since the rashes typical of the disease can be mistaken for other skin diseases and its histologic characteristic is indiscernible from other angioproliferative disorders.

Recent technological innovations address the problem of power consumption by the development of solar powered devices. In a research published in Scientific Reports, Li Jiang and colleagues have developed a solar thermal PCR device which utilizes energy from sunlight for thermal cycling used for nucleic acid amplification. The device addresses the energy burden of using highly sophisticated technology.

The solar powered PCR device, called KS-Detect (KS for Kaposi Sarcoma),  has a glass lens which is 75mm in diameter and has a movable 50mm diameter PCR chip. Its 100° tilting stage allows the device to be strategically positioned to face the sunlight and be able to gather and store energy.

Once the DNA samples have been obtained, it is then cycled. The temperature for the cycling process is controlled by moving the sample in and out of the light hotspot. Once the amplification process is done, a PCR dye called SYBR Green is applied on the sample to detect the presence of the target sequence. The sample glows green under UV light if the specified DNA segment is present. A photo of the glowing sample is then taken using a smartphone to be analyzed and processed to yield the results.

Since the device is sunlight driven, it allows for a 100-fold reduction in energy usage as compared to the use of current high end medical diagnostic devices. The biomedical science researchers stated that the PCR device can be powered by the standard battery of a smartphone for up to 70 hours. Furthermore, the study showed that the process only takes as fast as 30 minutes. This is especially advantageous in the employment of the device in hard to reach areas where travel time and distance may be hindrances to maintain follow up schedules. Moreover, by removing a number of electrical components such as microheaters and actuators, the device may prove to be advantageous not only in being energy efficient but also in its simplicity and potentially cost effective technology.



Li Jiang, Matthew Mancuso, Zhengda Lu, Gunkut Akar, Ethel Cesarman, David Erickson. “Solar thermal polymerase chain reaction for smartphone-assisted molecular diagnostics.” Scientific Reports (2014).

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