Nature-Inspired Engineering

Nature serves as an inspiration in practically every discipline. Engineering is no exception. Recently researchers from MIT designed a "tree-on-a-chip," a device that passively pumps water. This chip is based on the mechanism by which trees and other plants absorb water in their leaves, shuttle sugar down to their roots, and circulate nutrients throughout their tissues. Requiring no external parts or pumps, the chip has the capacity to act passively; pumping water and sugar at steady rates for several days.

The Design & Mechanism

The tree-on-a-chip was designed to mimic all elements of a tree's pumping system, namely the xylem, phloem, and leaves. This last specification, the leaves, serves the valuable role of producing sugar, an element left out of previous (unsuccessful) designs of microfluidic pumps. The structure of the chip consists of dual plastic slides sandwiched together, through which micro channels are drilled, mimicking the xylem and phloem. The xylem channel is filled with water, and the phloem channel with water and sugar. Separating the two slides is a semipermeable substance, designed like the actual membrane that exists between the xylem and phloem. A second membrane was set above the phloem channel slide, with a sugar cube on top to signify the extraneous sugar source circulating from the tree's leaves down to the phloem. The chip was attached to a tube, to allow water to travel from the tank to the chip. This design improved the constant flow rate duration from multiple minutes to multiple days.

The Implications

Dr. Anette "Peko" Hosoi, professor of Mechanical Engineering at MIT, notes that the passive action of the chip may make it useful as a rudimentary hydraulic actuator for miniature robots. To clarify, an actuator is a mechanical component whose purpose is the movement or control of a mechanism. Acting as a hydraulic actuator, the chip would offer a simple, inexpensive solution to a current problem; that being the difficulty and cost of manufacturing small, active parts and pumps to fuel the intricate movements of micro robots. "The goal of this work," noted Hosoi, "is cheap complexity, like one sees in nature...if we could make the building blocks that enable cheap complexity, that would be super exciting. I think these [microfluidic pumps] are a step in that direction." With this compelling research, it's clear that sometimes the best solutions come from the simplest places, and include the simplest ingredients. Who knows, sugar may be the future of micro robotics! Sometimes science is just so sweet.

Source: Nature Plants journal, Massachusetts Institute of Technology, and Science daily.