Introduction

The goal of this project is to design a mattress that can provide cooling effects to the user for a prolonged time. The three most common types of mattresses are spring, foam and hybrid which differ in their construction. The components of a mattress are divided into two layers: support layers on the bottom and comfort layers on top. Spring mattresses use springs for both the support and comfort layer. Similarly, foam mattresses use foam for both layers. Hybrid mattresses typically use springs as the support and foams for comfort. Due to their superior comfort and feel, foam-based mattresses are highly demanded by consumers. Achieving more breathable or heat dissipating foam and hybrid mattresses is a major goal for the bedding industry.

The cooling effects of a mattress depend on the materials used and the air flow. Most of the cooling effects of a mattress are determined by the materials used in the comfort layer. Memory foam mattresses tend to be the hottest while spring mattresses are the coolest. A spring mattress is cooler as space between the coil wires allows for more air to flow. In contrast, foam mattresses retain the most heat as a lack of air flow inhibits heat loss [1]. Foam also acts as a thermal insulator, stopping heat transfer away from the body. For these reasons, designing a memory foam comfort layer with improved air flow and heat transfer properties is imperative to the creation of a cooler mattress.

Motivation for Study

Overheating while sleeping is a significant problem for many people and poses health risks that range from diminished sleep quality to more serious illnesses in young children and the elderly. Excessive temperature is often caused when mattresses trap and reflect body heat back towards users, resulting in a positive feedback loop. This effect is particularly detrimental in parts of the world with humid heat exposure, because the body’s ability to wick away heat through sweat is blocked by the presence of excess air moisture [2]. The most common health implications of overheating are diminished quantities of all sleep stages, which humans require for learning, memory retention, and body recovery.

Problem Description

Overheating while sleeping is due to the mattress warming up to body temperature and a large portion of body surface area staying in contact with the mattress, inhibiting perspiration and cooling. The buildup of humidity in the sleeper’s micro-climate (the climate conditions between the mattress and sheets) also makes the air under the sheets feel much hotter than it is.

Limited air flow and heat dissipation is major contributor to a mattress’ inability to regulate temperature. Memory foam has the biggest issue with regulating temperature and air flow because as it compresses, the cavities in the foam collapse and the layer becomes dense, restricting air flow.

Design Objective

Our group aims to improve the cooling properties of a mattress through the selection of sustainable bedding materials that will match or improve the cooling properties of current Serta Simmons mattresses. Most mattresses don’t literally cool the sleeper, instead they are designed to maintain as low a temperature as possible while in contact with the sleeper. For the best sleep, maintaining a temperature where the human body is in an environment where it does not expend or release energy to maintain its core temperature is key. This environment is thermoneutral. The thermoneutral temperature is about 84 °F for a naked human [3]. By selecting materials that keep the bed around this temperature, we can design a mattress that provides a cooler sleeping experience.

In designing our solution, we will consider both materials and device design. Selecting the right layer material to the cooling capabilities of the mattress involves choosing a material that with improved air flow, high heat capacity and conductivity, and moisture wicking capabilities. Successfully integrating these materials into a full mattress will require us to design a device to contain and manufacture our proposed solution.