Lab on a Chip Blog

Malaysian scientists have created a flexible and environmentally friendly microfluidic device using a cloth decorating technique for printing wax onto cotton.

Dedy Wicaksono at the University of Technology Malaysia was inspired by his batik-patterned clothes to create the device. ‘Batik processing is wax patterning to create regions of differing hydrophilicity and hydrophobicity on cloth,’ says Dedy. The technique is traditionally used to prevent dye spreading from one area of cloth to another, creating coloured patterns. Using wax printing methods for paper and silk based microfluidic devices is known, but these have required specialist equipment or expensive materials.

Wicaksono’s method needs neither of these things. First, his team prepared the cotton by scouring it with sodium hydroxide and anhydrous sodium carbonate solutions. The treatment removes the outer layer, exposing underlying cellulose fibres. Both the chemical composition (increased oxygen content) and physical structure (increased surface roughness) of the fibre surface were altered, increasing the wettability and wicking rate.

Then, they printed the pattern for the microfluidic device onto paper. The paper was dipped into hot batik wax, then dried, before the pattern was cut from the sheet and attached to the scoured cloth using a few pins. Heat treatment melted the wax again, and it spread onto the surface and into the cloth, filling the gaps in the weave and within the fibres. The fatty acids in the wax increase the hydrophobicity of the fibres where they are applied, creating barriers to liquid flow.

Dedy’s group made both 2D and 3D devices; the latter was made by folding layers of the patterned cloth. A test using ink solutions revealed the ink moving along the cloth’s hydrophilic channels, filling a device in minutes. In a further test, the team was able to detect the protein bovine serum albumin colorimetrically using the devices, with the result visible to the naked eye.

‘A key innovation here is the batik-inspired method of transferring patterned wax on paper to cotton cloth,’ comments Shashi Murthy, an expert in microfluidic devices at Northeastern University, US. He adds that the technology ‘has the potential to provide a rapid and low cost readout for analytes characterised by relatively simple colorimetric assays’.

Dedy is now investigating ways to exert more control over the liquid flow so that more complex microfluidic devices can be developed. ‘By making the channels inside a flexible cloth, we are envisioning an embeddable wearable lab in the very near future,’ he says.

Flexible microfluidic cloth-based analytical devices using a low-cost wax patterning technique
Azadeh Nilghaz, Dedy H. B. Wicaksono, Dwi Gustiono, Fadzilah Adibah Abdul Majid, Eko Supriyanto and Mohammed Rafiq Abdul Kadir
Lab Chip, 2012, Advance Article
DOI: 10.1039/C1LC20764D

Original article published at Chemistry World

The study of brain development and degeneration is hindered by a lack of physiologically realistic models. French scientists have now developed a way to reconstruct neuronal networks in a microfluidic system to more closely mimic the directional neuronal pathways found in the brain.

Current experimental brain models include neuronal cell cultures and whole animal models; however, the former lack the complex architecture found in vivo, and the latter restrict studies at the cellular level. Aiming to bridge the gap between these models, Jean-Louis Viovy of the Curie Institute, Paris, and coworkers have developed a microfluidic device that allows for the growth of oriented and functional synaptic connections in vitro.

The device consists of two cell culture chambers connected by microchannels, through which axons – nerve fibres that conduct impulses away from the body of the nerve cell – can penetrate to form neuronal networks. In previous setups, replication of the unidirectional networks found in vivo could not be achieved since axons were sent from each chamber to the one opposite, travelling in both directions across the microchannel.

Inspired by the observation that axons can be mechanically constrained, the team modified the device to include asymmetric, funnel-shaped microchannels, termed ‘axon diodes’, to allow axons to grow from only one chamber to the other and not the opposite way. The concept was verified by experiments with mouse cortical neurons, in which the axon projection was 97 per cent selective for the ‘correct’ direction.

Next, by seeding cortical neurons (from the outer part of the brain) on the emitting side of the device and striatal neurons (from the inner part of the brain) on the receiving side, the team demonstrated the reconstruction of an active neuronal pathway involving two different neuronal subtypes. Furthermore, these networks were routinely maintained for three weeks in vitro, which would allow for both short and long-term experimentation.

‘I was struck by the simplicity of the system, it is beautiful,’ remarks Bonnie Firestein, an expert in cellular neurobiology from Rutgers University, New Jersey, US. ‘It is very easy to make and to use, and allows the recreation of what happens in vivo in an in vitro system.’

Such a device has many potential applications in neurobiological research. An initial motivation for this work was the requirement of a model to study the progression of neuronal damage in degenerative diseases such as Alzheimer’s. Additionally, Viovy believes the system is also an important platform for research into brain development and cognitive science. ‘How neurons communicate regarding information transmission is also an area in which we currently lack a model of the kind we have proposed here,’ he says. The team are currently working on further increasing the complexity of the networks, to more accurately model the neuronal organisation of the brain.

Interested? Read Sarah Farley’s full Chemistry World article here or download the Lab on a Chip paper:

Axon diodes for the reconstruction of oriented neuronal networks in microfluidic chambers
Jean-Michel Peyrin, Bérangère Deleglise, Laure Saias, Maéva Vignes, Paul Gougis, Sebastien Magnifico, Sandrine Betuing, Mathéa Pietri, Jocelyne Caboche, Peter Vanhoutte, Jean-Louis Viovy and Bernard Brugg
Lab Chip, 2011, Advance Article
DOI: 10.1039/c1lc20014c