Induction-Heating PCR Chip Cracks Worm Genes in 30 Minutes

A team of chemical engineers at Myongji University in South Korea has built a miniature genetic analysis platform that replaces the bulky heating blocks of conventional laboratory thermocyclers with wireless induction heating, the same physical principle that warms the pan on an induction cooktop. In a study published in Advances in Industrial and Engineering Chemistry, the researchers showed that their device can crack open the cells of the microscopic roundworm Caenorhabditis elegans, release its genomic DNA, and amplify a target gene segment in a complete polymerase chain reaction that finishes in just over thirty minutes. The entire system ran on a modest 12-volt input at less than 25 watts of power, a figure that stands in sharp contrast to the energy appetite of benchtop instruments and hints at a future in which sensitive genetic diagnostics could be carried out far from any well-equipped laboratory.

The motivation behind the work is rooted in a long-standing bottleneck in molecular diagnostics: the separation of sample preparation from amplification. Before any PCR can begin, cells must first be lysed, meaning their membranes and structural barriers must be disrupted so that nucleic acids spill out into solution. Traditional lysis techniques, including rotating blades, ultrasonication, bead milling, liquid homogenization, and repeated freeze-thaw cycles, are effective at industrial scale but demand heavy equipment, high energy input, and careful maintenance. When the COVID-19 pandemic exposed how fragile the diagnostic supply chain really was, clinical samples had to shuffle between separate stations for collection, lysis, extraction, amplification, and readout, producing turnaround times of at least four to six hours and sometimes stretching beyond twenty-four hours for standard real-time RT-PCR assays. Consolidating those steps into a single compact chip has therefore become one of the most actively pursued goals in the field.

Induction heating has long tempted microfluidics researchers because it transfers energy into a sample without any physical contact. An alternating current flowing through a primary coil generates an oscillating magnetic field, which in turn induces eddy currents in any nearby conductive material. Those currents dissipate energy as heat throughout the volume of the metal, warming the surrounding liquid quickly and uniformly. Earlier attempts to harness this effect for cell lysis and PCR, however, stumbled over two practical problems: the coils demanded prohibitively high power to reach useful temperatures, and the heating process was too slow to be clinically useful. The Myongji team, led by corresponding authors Yongmin Cho and Hyun Ho Lee, attacked both limitations with a clever three-part heating architecture that has no direct equivalent in prior designs.

The heart of the system is a trio of conductive components arranged around a standard 0.2-milliliter PCR microtube. The primary, or external, coil is a ten-turn spiral of polyimide-coated copper wire, one millimeter in diameter, wrapped around the outside of the tube with a coil diameter of 22 millimeters and a length of 30 millimeters. Inside the tube sits a miniature secondary coil, a thirty-turn winding of polyimide-coated iron wire just 0.05 millimeters in diameter, small enough to rest at the bottom of the microtube under gravity. Beneath the tube, completing the arrangement, is a subsidiary copper ring four millimeters in diameter and five millimeters tall. When alternating current energizes the external coil, the resulting magnetic field induces heating both directly in the internal coil and indirectly in the copper ring, generating a volumetric heating effect that bathes the sample from multiple directions at once. A temperature sensor positioned beneath the microtube, in contact with the copper ring, tracks the thermal cycle in real time.

The internal coil proved to be the decisive innovation. In comparative experiments with deionized water, the researchers measured the rate at which the liquid warmed under induction heating with and without the secondary coil present. With the coil inside the tube, the temperature climbed 3.5 times faster, because the alternating magnetic field coupled directly into the metal winding immersed in the sample rather than relying on slower indirect transfer through the tube wall and the copper ring alone. Thermal imaging with an infrared camera confirmed that the microtube reliably reached the two temperatures required for the lysis protocol, 60 degrees Celsius and 90 degrees Celsius. Because the internal coil simply sinks to the bottom of the tube by gravity, no wiring, clamping, or complex mechanical fixture is needed, which keeps the design compatible with disposable, low-cost consumables and leaves wide freedom in material selection for future chip-based versions.

To test the platform on a real biological sample, the team turned to C. elegans, the millimeter-long nematode whose fully sequenced genome, transparent body, genetic similarity to humans, and ease of handling have made it a workhorse of molecular biology. Worms were grouped into samples of 10, 20, 30, and 50 individuals, mixed with 50 microliters of a lysis cocktail containing potassium chloride, Tris buffer, magnesium chloride, the nonionic detergents NP-40 and Tween-20, and gelatin. Each sample was first snap-frozen at minus 80 degrees Celsius for ten minutes, a freeze-crack treatment that mechanically ruptures the tough worm cuticle, and then subjected to thermal lysis consisting of one hour at 60 degrees Celsius followed by fifteen minutes at 90 degrees Celsius. The researchers ran identical lysis protocols on both their induction platform and a conventional heat block for comparison, measuring the released nucleic acids with UV-Vis spectroscopy and visualizing them by agarose gel electrophoresis.

The results told a nuanced story. On the gel, distinct ribosomal RNA bands appeared, and their fluorescence intensity rose in step with the number of worms in the tube, confirming that nucleic acid release scaled with sample input. Even ten worms yielded a detectable band, while the 50-worm sample produced a strong, clear signal. Intact C. elegans genomic DNA, at roughly 100 megabases, is far too large to migrate into the gel, so it aggregated near the loading wells as a faint smear, exactly as expected. The spectrophotometric ratios, however, revealed a trade-off: the absorbance ratio at 260 and 280 nanometers, a standard gauge of nucleic acid purity against protein contamination, was about 0.678 for induction-lysed samples versus 0.983 for the heat block. The induction lysate therefore carried somewhat more residual protein, and the purity improved only gradually as more worms were added, from 0.147 with ten worms to 0.598 with thirty. The authors note candidly that this lower purity could reduce PCR efficiency and that the lysis chemistry will need refinement.

Where the platform truly shone was in amplification speed. Using the induction lysate directly, the team performed a two-step PCR targeting the act-1 gene, a cytoskeletal actin gene of C. elegans, with primers verified against the NIH primer-BLAST database. The thermal profile held stable across forty cycles, cycling between denaturation at 95 degrees Celsius and a combined annealing-and-extension step, with the abstract noting stable maintenance of denaturation, annealing at 60 degrees, and extension at 72 degrees across the full program. The entire amplification finished in 30 minutes and 27 seconds, a reduction of more than fifty percent compared with the sixty to ninety minutes typically consumed by conventional Peltier-based thermal cyclers, which heat and cool a metal block by semiconductor-driven heat pumping rather than generating heat within the sample itself. Gel electrophoresis revealed the expected 133-base-pair product, and a separate primer set yielded the anticipated 1875-base-pair fragment, demonstrating that the system could amplify both short and long targets from worm genomic DNA.

Equally important was what the experiments ruled out. Skeptics might worry that a metal coil floating inside the PCR cocktail would poison the polymerase, distort the reaction chemistry, or interfere with amplification. To check, the researchers deliberately placed the internal coil in tubes processed on an ordinary heat-block incubator and ran a 90-minute PCR alongside the induction-heated reaction. The gel bands were indistinguishable between the two methods, proving that the presence of the secondary coil inside the microtube has no adverse effect on the PCR itself. The team does acknowledge a practical ceiling: the current internal coil is too large relative to reaction volumes below about 20 microliters, so miniaturizing further will require redesigning the inductive element for tinier volumes.

The authors position the work as an early but concrete step toward a one-pot diagnostic platform in which lysis, amplification, and eventually detection coexist in a single disposable tube. Because induction heating is wireless and contact-free, it minimizes contamination risk, simplifies fabrication, and sidesteps the thermal instability, complex sample handling, and high cost that plague microchip-based PCR alternatives. The researchers suggest that modifying the internal coil could integrate enzymes or other functionalities directly into the heating element, and they outline next steps including optimized thermal control and validation on genomic DNA from mammalian cells and microorganisms. If those efforts succeed, the humble physics of a cooking hob, scaled down to a copper coil and an iron wire thinner than a human hair, could help put rapid genetic analysis within reach of clinics, farms, and field stations that will never host a full-sized thermocycler.

Subject of Research: A low-power induction-heating platform for integrated cell lysis and PCR of C. elegans genomic DNA

Article Title: Efficient cell lysis and PCR platform with induction heating for C. elegans gene analysis

Article References: Hong, S., Uh, J., Kang, M., Kim, T., Kwon, Y., Cho, Y., & Lee, H. H. (2025). Efficient cell lysis and PCR platform with induction heating for C. elegans gene analysis. Advances in Industrial and Engineering Chemistry, 1(1), Article 33. https://doi.org/10.1007/s44405-025-00032-x

Image Credits: AI Generated

DOI: 10.1007/s44405-025-00032-x

Keywords: induction heating, PCR, cell lysis, C. elegans, genomic DNA, point-of-care diagnostics, microfluidics, thermal cycling, molecular diagnostics, act-1 gene, low-power devices, biotechnology