Biofoams are biological or biologically derived foams, making up lightweight and porous cellular solids. A relatively new term, its use in academia began in the 1980s in relation to the scum that formed on activated sludge plants.

Biofoams is a broad umbrella term that covers a large variety of topics including naturally occurring foams, as well as foams produced from biological materials such as soy oil and cellulose. Biofoams have been a topic of continuous research because synthesized biofoams are being considered as alternatives to traditional petroleum-based foams. Due to the variable nature of synthesized foams, they can have a variety of characteristics and material properties that make them suitable for packaging, insulation, and other applications.

Foams can form naturally within a variety of living organisms. For example, wood, cork, and plant matter all can have foam components or structures. Fungi are generally composed of mycelium, which is made up of hollow filaments of chitin nanofibers bound to other components. Animal parts like cancellous bone, horseshoe crab shells, toucan beaks, sponge, coral, feathers, and antlers all contain foam-like structures which decrease overall weight at the expense of other material properties.

Structures like bone, antlers, and shells have strong materials housing weaker but lighter materials within. Bones tend to have compact, dense external regions, which protect the internal foam-like cancelous bone. The same principle applies to horseshoe crab shells, toucan beaks, and antlers. The barbs and shafts of feathers similarly contain closed-cell foam.

Protective foams can be formed externally by parent organisms or by eggs interacting with the environment: tunicate egg mix with sea water to create a liquid-based foam; tree frog eggs grow in protein foams above and on water (see Figure 1); certain freshwater fish lay eggs in surface foam from their mucus; deep sea fish produce eggs in swimbladders of dual layered foams; and some insects keep their larvae in foam.

Honeycomb refers to bioinspired patterns that provide a lightweight design for energy absorbing structures. Honeycomb design can be found in different structural biological components such as spongy bone and plant vasculature. Biologically inspired honeycomb structures include Kelvin, Weaire and Floret honeycomb (see Figure 2); each with a slightly different structure in comparison to the natural hexagonal honeycomb. These variations on the biological design have yielded significantly improved energy absorption results in comparison to traditional hexagonal honeycomb biofoam.

Due to these increased energy absorption performances, honeycomb inspired structures are being researched for use inside vehicle crumple zones. By using honeycomb structures as the inner core and surrounding the structure with a more rigid structural shell, these components can absorb impact energy during a crash and reduce the amount of energy the driver experiences.

Aerogels are able to fill large volumes with minimal material yielding special properties such as low density and low thermal conductivity. These aerogels tend to have internal structures categorized as open or closed cell structures, the same cell structure that is used to define many 3-dimensional honeycomb biofoams. Aerogels are also being engineered to mirror the internal foam structures of animal hairs (see Figure 3). These biomimetic aerogels are being actively researched for their promising elastic and insulative properties.