Butterflies and moths, constituting the order Lepidoptera, have inspired decades of engineering research in aerodynamics, optics, and navigation. This project focuses on the lepidopteran proboscis, which is poorly explored from an engineering perspective. The goal is to develop fundamental principles of fiber-based microfluidics inspired by the lepidopteran fluidic system, and apply these principles to the design, fabrication, and manipulation of a new class of fiber-based devices capable of transporting and probing a previously impossible range of liquids. These principles will be validated using biological data from Lepidoptera. Through collaboration of engineers, chemists, and biologists, bioinspired proboscises will be fabricated by taking advantage of modern fiber technology, which offers fiber multifunctionality such as mechanical/electromagnetic memory, improved absorbency, and controlled wettability. A biomimetic approach will be developed for actuation, sensing, and control of the synthetic proboscis. The advantages will be illustrated for an artificial proboscis to probe fluids from individual vascular smooth muscle cells. The lepidopteran fluidic system is envisioned as shifting the current microfluidic paradigm from stationary channel-like structures to fiber-based microfluidic devices, providing distributed actuation, sensing, and manipulation with minute amounts of fluids. The project will serve as a catalyst for development of novel science, engineering, and technology at the interface of biology, chemistry, materials science, and mechanical, electrical, and bioengineering. The basic principles, identified by a multidisciplinary group, will impact multiple fields, including (i) integrative biology by providing insight into the physical function of the lepidopteran fluidic system, (ii) materials science by offering new knowledge on fluid-fiber interactions and relevant fiber design parameters, (iii) robotics and control by developing biomimetic methods for shape and fluid control, and (iv) bioengineering by developing proboscis-inspired tissue-fluid probes. The basic principles can be applied to the design of a wide range of future devices, as in applications requiring low-volume fluid retrieval and analysis coupled with controlled manipulation, such as environmental monitoring and biomedical and forensic probing.
The structure of the butterfly proboscis presents a paradox. The proboscis needs to be slender to enter narrow floral tubes and generate capillary forces to pull in the nectar, but it must be large enough to facilitate flow. A detailed analysis of the food-canal morphology and experimental measurements of transport properties of the proboscis indicate that pressures greater than 1 atmosphere are needed for fluid flow in a resting proboscis. Our observations of the feeding behavior of butterflies, using X-ray phase-contrast imaging at Argonne National Laboratory and high-speed optical microscopy, provided insights into how the 1-atmosphere limitation can be overcome. We discovered that the sizes of the pores in the distal portion of the proboscis are altered by sliding the galeae against each other. Another discovery concerned the hydrophobic/hydrophilic dichotomy of the proboscis materials. A new mechanism of food acquisition based on partitioning of the liquid column by bubble trains also was revealed. Thus, butterflies with their small, thin, tapered, and deceptively passive-looking proboscises can behaviorally overcome potential mechanical restrictions and modify the functional range in ways not previously imagined. We successfully fabricated artificial proboscises, based on the insights and ideas gained from these studies of the natural feeding devices of biological organisms. These artificial proboscises were validated as probes that are able to detect mRNA at concentrations corresponding to the level in a single cell. This is a first successful step toward the development of highly efficient fiber-based PCR probes for gene-expression analysis, confirming that the artificial proboscises are able to absorb minute amounts of mRNA, with PCR providing reliable and reproducible data. A rich library of synthetic materials has been employed to fabricate artificial proboscises. We modeled and developed magnetic fiber-based grabbers that are able to perform as artificial proboscises with a controlled positioning of their tips, using a magnetic field. Different modes of operation of this autonomous grabber have been modeled, designed, and tested in experiments to show the robustness of these artificial proboscises. The collaboration among biologists, materials scientists, and engineers provided new insights and applications of technical tools for testing hypotheses about the function of butterfly proboscises. The collaboration also enabled the application of these fundamental findings to engineering problems related to the development of artificial proboscises for probing minute amount of fluids. The work laid the groundwork for establishing a model of successful interactions between researchers working in life sciences and engineering. These tight interactions allowed disparate groups to look at the challenging problems in their professions from a different perspective. This project generated groundbreaking discoveries that challenged common textbook knowledge. It provided broad public interest, evident from the media coverage. Students successfully defended their MS (2) and PhD dissertations (4). Postdocs earned academic (1) and industrial positions (3). Undergraduates and high school students regularly participated in the research. This project ignited the interest of a broad scientific community and attracted the attention of a diverse community of biologists, chemists, physicists, and engineers. Two successful international symposia (2011, 2013) on the core research topic were organized by the Principal Investigators. The research provided examples for the social sciences of the need and value of preserving biodiversity and for serving as stewards of Nature because of the vast potential to acquire insights and solutions to some of society’s major challenges. Our work with natural and artificial proboscises has implications and applications for enhancing medical diagnoses by using less invasive nano- and microsampling devices. The work provides the potential for developing commercial samplers based on Nature’s engineering solutions.
