The mixing of oil and water is generally something most of us have no use for, with the two known to be immiscible liquids—meaning they do not combine together and eventually separate into layers. Researchers at Lawrence Berkeley National Laboratory are currently studying how these types of mixtures could be helpful in a variety of different scientific applications though. Their findings are discussed in a recently published paper, ‘Harnessing liquid-in-liquid printing and micropatterned substrates to fabricate 3-dimensional all-liquid fluidic devices,’ authored by Wenqian Feng, Yu Chai, Joe Forth, Paul D. Ashby, Thomas P. Russell, and Brett A. Helms.
In harnessing liquid structures to create 3D fluidic devices, the researchers explained that such an exercise is an ‘emerging design paradigm’ for chemists today interested in manipulating soft matter and figuring out ways to produce them on demand.
“Still nascent in their development, structured liquids presently lack clear design rules for controlling their 2D or 3D architectures, spatially directing functional components within each liquid phase, and coupling physiochemical processes across the liquid−liquid interface so as to create autonomous chemical systems capable of performing useful work, processing information, or executing logical functions,” state the scientists.
To make such devices, glass supports were coated with superhydrophobic polymers. Next, the researchers used photo-patterning with superhydrophilic channel architectures, also accompanied by an aqueous dispersion of anionic 2D nanoclays.
“Interfacial forces are effective in pinning and confining the aqueous phase in arbitrarily complex geometries and a wide range of channel widths,” stated the research team.
The manipulated systems are able to reach the desired steady state quickly, and nanoparticle−polymer surfactants (NPS) topography was presented after the researchers employed atomic force microscopy. They reported that their data demonstrated ‘well-packed nanoclays’ at the interface with no structural problems. The researchers also noted that only microchannels with NPS walls could guide flow at the desired rate. Without them, the aqueous phase proceeded to build up at the channel entrance. The team also noted that maximum flow is completely reliant on the channel’s cross-section and overall architecture.
The team also went on to investigate membrane permeability, functionalization, and further chemical transformations regarding the fluidic devices with the requisite NPS walls. With the use of NPS films, they found that added microchannels were ‘straightforward to introduce’ direct-write methods.
“To contextualize this advance, without the aid of micropatterned substrates and NPS films, constructing channel-like aqueous threads in oil is not typically possible, as the thermodynamic driving force required to reduce interfacial area breaks up aqueous threads into droplets,” stated the researchers.
The fabricated microchannels offered such a stable structure during research and evaluation that the researchers found they could use them as bridges either connecting separate regions on the substrate, or in connecting the device to an exogeneous entity.
“Our studies uncover a latent learning ability in such devices, in that physiochemical sensing or detection of channel properties and contents can be used to direct the architecture of the device to achieve a specific outcome. Maturation of the design concept led to devices that can execute complex tasks in a logical manner by reversible compartmentalization of function and direction of chemo-energetic flows that operate far from equilibrium conditions,” concluded the researchers.
“The potential for this system to exhibit autonomous learning is evident. Such devices may also be arrayed to generate deep or dark data for machine learning, e.g., from all-liquid (bio)chemical transformations and screens, to build knowledge and understanding from chemical logic.”
Fabrications methods used in 3D design and 3D printing today span many different industries and intricate applications, but you may be surprised to explore further into the science of materials, hardware, and software, and realize how many chemists are using the technology from use in continuous flow systems to studies centered around miniaturization and complex designs in microfluidics. Learn more about current processes in liquid-in-liquid printing here.
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