Nature-inspired chemical engineering, a transformative methodology for innovation

Some of our greatest challenges involve clean energy, water, the environment, dwindling resources, sustainable manufacturing, and healthy ageing. To approach them, chemical engineers are well equipped with the basic tools: balances, systems modeling, thermodynamics, kinetics and transport phenomena. Nevertheless, how these tools are employed in process and product design requires rethinking. Tackling Grand Challenges requires step-changes through transformative approaches and lateral thinking across disciplines, beyond incremental variations on traditional designs. Nature is filled with well-integrated, “intensified” systems, optimized over the eons, to satisfy stringent constraints for survival by scalable processes with emergent properties. We propose to take nature as a source of inspiration, leveraging fundamental mechanisms underpinning desirable properties (like scalability, resilience or efficiency) and applying these to engineering designs, with suitable adaptations to satisfy the different contexts of technology and nature. We call this approach Nature-Inspired Solutions for Engineering (NISE), and its application to chemical engineering problems Nature-Inspired Chemical Engineering (NICE) [1]. The need to think about the context of technological applications, and the consistent use of fundamental scientific insights rather than superficial similarities, sets nature-inspired engineering apart from biomimetics or biomimicry. Examples from architecture and structural engineering will be given to illustrate this difference [2]. This lecture will introduce NICE as a systematic methodology [1] that is thematically structured around ubiquitous, fundamental mechanisms in nature, in particular: (T1) hierarchical transport networks, (T2) force balancing, (T3) dynamic self-organization, and (T4) control mechanisms in ecosystems, biological networks and modularity. Thus, NICE looks at nature with the eyes of an engineer, employing scientific tools to derive nature-inspired concepts that are, subsequently, systematically used in the nature-inspired design of solutions to real problems, aided by mathematical and computational modeling and experimentation. In our examples, we will see how we learn from trees, lungs, kidneys, and dunes to intensify chemical and energy processes, and how we discover materials for biomedicine and the built environment, using the NICE methodology [1-6]. The NICE approach is powerful, because it allows us to merge creativity with rational design. Being thematic and systematic, once validated for one problem, NICE can be employed to solve various similar problems in other fields, e.g., from fluidized beds to fuel cells, and from catalysts to dental materials. Ultimately, the NICE methodology is a practical pathway for innovation and design. References [1] M.-O. Coppens, 2012, A nature-inspired approach to reactor and catalysis engineering. Curr. Op. Chem. Eng. 1, 281-289. [2] A.S. Perera and M.-O. Coppens, 2018, Re-designing materials for biomedical applications: From biomimicry to nature-inspired chemical engineering. Phil. Trans. Roy. Soc. A. 377(2138): 20180268. [3] M.-O. Coppens and G. Ye, 2018, Nature inspired optimization of transport in porous media. In Diffusive Spreading in Nature, Technology and Society (ed.: A. Bunde, J. Caro, J. Kärger and G. Vogl), Springer. [4] P. Trogadas, M. Nigra and M.-O. Coppens, 2016, Nature-inspired optimization of hierarchical porous media for catalytic and separation processes. New J. Chem. 40, 4016-4026. [5] K. Wu, L. de Martín and M.-O. Coppens, 2017, Pattern formation in pulsed gas-solid fluidized beds - the role of granular solid mechanics. Chem. Eng. J. 329, 4-14. [6] P. Trogadas, J.I.S. Cho, T.P. Neville, J. Marquis, B. Wu, D.J.L. Brett and M.-O. Coppens, 2018, A lung-inspired approach to scalable and robust fuel cell design. Energy & Env. Sci. 11, 136

A vacuum set-up for fundamental studies of self- and transport diffusion in porous media

Here, we propose experiments that emulate processes that occur in disordered mesoporous media, on a macroscopic scale, by using a special designed high-vacuum system and 3D-printed channels to investigate features of complex porous media, such as fractal pores [3]. This set-up allows us to validate Knudsen diffusion theory in complex geometries more directly than has ever been the case. Some preliminary results will be shared, including features of the vacuum set-up, and Knudsen diffusion results in channels of varying geometry, including channels with a 3D-printed fractal surface

Cell Membrane‐Inspired Graphene Nanomesh Membrane for Fast Separation of Oil‐in‐Water Emulsions

Graphene exhibits fascinating prospects for preparing high-performance membranes with fast water transport, due to its low friction with water and extreme thinness. However, for graphene-assembled membranes, each molecule passing through the membrane should bypass many graphene sheets, which lengthens the molecular pathways and increases the mass transfer resistance. Herein, a graphene nanomesh (GNM) membrane is fabricated that is inspired by cell membranes, including aquaporins with their hydrophilic gate for selective transport and hydrophobic channel for low friction with water, thus resulting in fast water transport, as well as hydrophilic polymer brushes on the membrane surface for fouling resistance. GNM is synthesized by etching nanopores on graphene oxide (GO) nanosheets to significantly shorten the water transport channels, whereas the hydrophobic graphene sheets lead to low water friction; in combination, ultra-fast, selective water flux is achieved. Also, hydrophilic polymer chitosan is utilized to modify GNM to construct a hydration layer, which suppresses foulants from touching the membrane surface. Accordingly, the permeance of the cell membrane-inspired graphene nanomesh membrane reaches almost 4000 L m–2 h–1 bar–1, which is about 260 times the permeance in a GO membrane, and the membranes show superior antifouling properties for separating various surfactant-stabilized oil-in-water emulsions

Nature-inspired chemical engineering processes

Nature is fascinating. It is even more awesome when scru-tinised from a scientific, mechanistic angle across lengthscales, down to the nanoscale, unravelling complex structuresand patterns. Natural systems consist of a dynamic, complexassembly of interacting components and systems, leadingto emergent behaviour, achieving tasks ultimately aiming atsurvival, which, very roughly, translates into sustaining cur-rent activities. Such activities include processing matter andenergy, transporting fluids, changing phase state to obtainproducts of high quality, and communication. The similar-ity is striking with what processes in chemical engineeringare intended for, since they also deal with the processing ofmatter, energy and data..

From Biomimicking to Bioinspired Design of Electrocatalysts for CO2 Reduction to C1 Products

The electrochemical reduction of CO2 (CO2RR) is a promising approach to maintain a carbon cycle balance and produce value-added chemicals. However, CO2RR technology is far from mature, since the conventional CO2RR electrocatalysts suffer from low activity (leading to currents 200 mA cm−2, >8000 h, >90 % selectivity). Significant improvements are possible by taking inspiration from nature, considering biological organisms that efficiently catalyze the CO2 to various products. In this minireview, we present recent examples of enzyme-inspired and enzyme-mimicking CO2RR electrocatalysts enabling the production of C1 products with high faradaic efficiency (FE). At present, these designs do not typically follow a methodical approach, but rather focus on isolated features of biological systems. To achieve disruptive change, we advocate a systematic design methodology that leverages fundamental mechanisms associated with desired properties in nature and adapts them to the context of engineering applications

Kidney-inspired membranes with superior antifouling properties

Membranes are a versatile separation technology, used in a multitude of industrial settings. They pose several inherent advantages, such as easy scale up and separation with no requirement for additives. This has caused increasing popularity in water purification and bio-separations. However, the major challenge of this technology is fouling, leading to a declining flux, which requires frequent, extensive cleaning to correct. Fouling is influenced by factors on different scales; macroscopically, the characteristics of the feed and the hydrodynamics of the membrane module will influence fouling. Interactions between foulants and the membrane surface, however, also affect fouling and are governed by fundamental physical forces, such as electrostatic interactions. Thus, all scales must be considered when designing membranes that are less prone to fouling. To solve this problem, we can turn to nature, which provides us with a treasure trove of clever solutions to a wide range of engineering problems, such as those experienced in membrane processes. The kidney, for instance, is a remarkable organ capable of producing over four million liters of effectively protein-free urine over a lifetime with no significant fouling (1). The glomerulus is a bundle of specialized blood vessels, which carries out the first stage of kidney filtration, the stage most comparable to membrane separations. Within the lumen of these blood vessels, a brush-like structure is present, composed of proteoglycans and glycoproteins, which are responsible for the overall negative charge and hydrophilicity of this layer. The glomerulus also has notable macroscopic properties that can create hydrodynamic regimes that promote the back transport of adsorbed foulants. The combination of the brush structure and the resulting hydrodynamics of the system are believed to be key causes behind the superior anti-fouling properties of the kidney. To translate this inspiration into membrane processes, the design that has been employed in this work is the grafting of polyelectrolyte polymer brushes as an antifouling layer onto commercial membranes. This grafting is achieved through surface-initiated controlled radical polymerization (SI-CRP) using ARGET ATRP (Activators Regenerated by Electron Transfer Atomic Transfer Radical Polymerization). The stimuli-responsive polymer brushes reduce fouling through steric and electrostatic repulsion, due to the negative charge of the layer in solvents. This has been demonstrated, thus far, in the filtration of silica nanoparticles and albumin as model foulants in water purification and bio-separations. In both cases, the flux decline over a fixed time for the polymer brush modified membranes showed significant improvement over the commercial membrane with maximum reductions in flux decline of 43% and 42% in the filtration of albumin and silica nanoparticles, respectively. The combination of other macroscopic influences, together with further optimization of the polymer brush antifouling layer, has the potential to leverage the superior antifouling properties of the kidney to synthesize a class of next-generation membranes. 1. Hausmann R et al. The glomerular filtration barrier function: new concepts. Curr Opin Nephrol Hypertens. 2012;21(4):441–9

Intensification of liquid mixing and local turbulence using a fractal injector with staggered conformation

Two self-similar, tree-like injectors of the same fractal dimension are compared, demonstrating that other geometric parameters besides dimension play a crucial role in determining mixing performance. In one injector, when viewed from the top, the conformation of branches is eclipsed; in the other one, it is staggered. The flow field and the fractal injector induced mixing performance are investigated through computational fluid dynamics (CFD) simulations. The finite rate/eddy dissipation model (FR/EDM) is modified for fast liquid-phase reactions involving local micromixing. Under the same operating conditions, flow field uniformity and micromixing are improved when a staggered fractal injector is used. This is because of enhanced jet entrainment and local turbulence around the spatially distributed nozzles. Compared with a traditional double-ring sparger, a larger reaction region volume and lower micromixing time are obtained with fractal injectors. Local turbulence around the spatially distributed nozzles in fractal injectors improves reaction efficiency