A new brand of feminine care pads is entering the U.S. market, featuring a patented, plant-derived alternative to the synthetic superabsorbent polymers (SAP) typically used in pad cores.

South Korean femtech company Inertia, founded in 2021 by female scientists from the Korea Advanced Institute of Science and Technology (KAIST), set out to address what it saw as a longstanding limitation in disposable period care: while visible materials evolved, the absorbent core remained largely unchanged. Instead of reformulating only the surface layer, the company engineered a bio-based core designed to replace the synthetic interior widely used across the category.

This resulted in the launch of Prism Pads, which use Inertia’s Labocell core technology, a cellulose-based absorbent matrix engineered to manage menstrual flow while remaining lightweight, breathable and flexible.

“Although many products today emphasize natural materials, in reality, most sanitary pads only use organic cotton in the top cover layer, while the internal absorbent core still relies heavily on synthetic polymers and conventional pulp-based structures,” says Inertia co-founder and CEO Hyoyi Kim.

When developing Prism Pads, Inertia sought to rethink both material transparency and absorbent performance from the ground up. As a result, Kim says the pads were designed using organic cotton nonwoven materials across multiple structural components, including the cover and wings, ensuring that the parts that directly touch the body are made from natural fibers.

At the same time, the brand developed Labocell technology to improve fluid absorption and distribution within the absorbent core. Within the absorbent layer, organic cotton is combined with the Labocell material, creating a structure that balances natural fiber comfort with advanced absorption performance.

“Our goal was to create a product that goes beyond surface-level material claims and instead integrates both natural materials and new absorbent technology into the overall design of the pad,” she says.

Developed by Inertia’s research team, Labocell is based on a cellulose-derived polymer hydrogel matrix. While many conventional absorbent cores rely on SAP particles or fiber-based pulp structures, Labocell works through a different mechanism.

“When liquid enters the absorbent layer, it diffuses into the porous hydrogel matrix and becomes trapped within the crosslinked three-dimensional network of the polymer, allowing the material to hold fluid efficiently without relying on particulate SAP,” Kim explains.

According to Kim, the organic cotton provides a soft, breathable structural layer, while Labocell enhances the pad’s ability to absorb and distribute fluid within the core. “As a result, the absorption performance of the pad is driven primarily by the hydrogel matrix inside the core rather than a traditional nonwoven fiber absorbent structure,” she adds. “This approach allows us to combine natural fiber materials with advanced absorbent technology in a single structure.”

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Beyond SAP

From a functional standpoint, Labocell serves the same fundamental purpose as SAP: absorbing and retaining fluid within the absorbent core of the product. However, Kim says most conventional SAP materials have historically been optimized for distilled water absorption, which differs significantly from menstrual fluid in terms of viscosity, cellular content and flow behavior.

Rather than focusing on water-based absorption performance, Labocell was engineered to perform effectively under the conditions of menstrual blood absorption. “Cellulose-based absorbent systems have long been explored as potential alternatives to SAP,” Kim explains. “In practice, however, their commercialization has been limited due to relatively low gel strength and higher material costs, which make it difficult to achieve both structural stability and manufacturing feasibility in hygiene products.”

Inertia’s research focused on overcoming these limitations by designing a cellulose-based absorbent structure optimized for menstrual fluid. Through this approach, the scientists were able to achieve practical absorption and retention performance while maintaining product stability and manufacturability.

Another consideration relates to material safety. Conventional SAP is synthesized through polymerization processes that may leave trace residual monomers, which in some cases have raised concerns about potential skin irritation in sensitive applications, Kim says. Labocell, by contrast, is based on a cellulose-derived material system, which reduces the likelihood of such residual monomer concerns.

Problem Solving

One of the main challenges for the scientists in developing the pads was maintaining a thin and flexible core structure while integrating the Labocell material into the absorbent layer. When hydrogel-based absorbent materials such as Labocell are directly applied to the absorbent core, the material can aggregate or form localized clusters, which may create uneven thickness within the pad.

To address this issue, Inertia developed a process that integrates Labocell with ECF pulp, allowing the material to be converted into a nonwoven-style sheet structure before being incorporated into the pad.

“By laminating the Labocell material with the pulp substrate, the absorbent layer can be distributed more evenly across the core structure,” Kim says. “This approach helps prevent material aggregation while maintaining the thin, breathable and flexible characteristics required for sanitary pad applications.”

Future Applications

While the underlying technology has the potential to be applied to other hygiene product categories, applications such as baby diapers and incontinence products present different technical requirements compared to sanitary pads. “These products must handle significantly larger fluid volumes, and the absorbent system must be optimized specifically for urine absorption, which has different characteristics from menstrual fluid,” she explains.

As a result, adapting the technology for these categories would require further optimization of the absorbent structure and material formulation to meet the performance demands of those products. Additionally, because these products typically use much larger quantities of absorbent material than sanitary pads, manufacturing scalability and cost efficiency become even more important considerations, she adds.

U.S. Market Entry

Beyond the materials science behind the product, Inertia has already established a significant commercial presence in its home market. Since launching in South Korea, Inertia has sold more than 10 million pads and established a strong retail and e-commerce presence. The Prism Pads rank as the #1 feminine care product at Olive Young, South Korea’s largest health and beauty retailer. The company saw the U.S. as a natural next step for international expansion.

“In recent years, consumers in the U.S. have shown increasing interest in material transparency, product safety and innovation in feminine care products,” Kim says. “Many consumers are paying closer attention to what materials are used in products that come into direct contact with the body.”

Prism Pads are available in Regular and Heavy absorbency options. In the U.S., pricing is $7.99 for an 18-count pack and $29.99 for a 40-count value pack. The products are available at www.inertiaofficial.com, with a subscription option, and on Amazon.