24 MOMENTUM • VIRGINIA TECH MECHANICAL ENGINEERING
Virginia Tech lab proves the concept of a natural approach to antiperspirants
Sweating is a natural function of the human body , allowing a body to cool itself as sweat emerges from glands and evaporates . Separately , this process may produce odors as bacteria present on the skin break down sweat proteins . A deodorant kills the bacteria that produce the odor , while an antiperspirant clogs sweat ducts to prevent sweat from emerging in the first place .
This clogging is commonly achieved by the use of metallic salts . There remains debate as to whether or not these metallic salts contribute to heath risks such as cancer , but demand by consumers for more natural alternatives to antiperspirants containing these metals ( a sort of “ just-in-case ” scenario ) is rapidly growing .
The Virginia Tech Nature-Inspired Fluids and Interfaces Lab , led by Associate Professor Jonathan Boreyko , has just made a major breakthrough in the study of natural antiperspirants . Their theory is this : If the sweat can begin to evaporate while still inside of the sweat duct , before it emerges onto the skin , the sweat ’ s own minerals will crystallize to clog the duct . In other words , the mixture of sodium , chloride potassium , calcium , urea , and bicarbonates naturally present in sweat can do the same work as the metallic salts used in commercial antiperspirants .
Testing the theory
To explore this idea , the group constructed an artificial “ sweat rig ” to investigate the possibilities . They used a microchannel made from pulled glass to serve as an artificial sweat duct , and created the function of a sweat gland by using pressurized gas to push synthetic sweat across tubing and into the connected glass duct .
To prove the concept , three different scenarios were tested . The first was a control , where no product was placed near the artificial sweat duct . For the second test , researchers placed a dry cube of the organic , silicon-based polymer PDMS near the exit of the duct . Finally , for the third test , the PDMS cube was infused with propylene glycol , a chemical that is highly attractive to water . These three scenarios allowed for a direct comparison of how sweat flowed when the duct was completely open , versus near a regular object , versus near an evaporation-inducing object .
The team observed the flow of the synthetic sweat , which has the same minerals as natural sweat , by focusing a microscope on the artificial duct . For the first two scenarios , the sweat flowed freely from the outlet of the sweat duct , which would correspond to sweat emerging onto the skin . But for the third scenario , where the duct was placed