A New Approach to In‐Situ “Micromanufacturing”: Microfluidic Fabrication of Magnetic and Fluorescent Chains Using Chitosan Microparticles as Building Blocks

Abstract

An in situ microfluidic assembly approach is described that can both produce microsized building blocks and assemble them into complex multiparticle configurations in the same microfluidic device. The building blocks are microparticles of the biopolymer chitosan, which is intentionally selected because its chemistry allows for simultaneous intraparticle and interparticle linking. Monodisperse chitosan-bearing droplets are created by shearing off a chitosan solution at a microfluidic T-junction with a stream of hexadecane containing a nonionic detergent. These droplets are then interfacially crosslinked into stable microparticles by a downstream flow of glutaraldehyde (GA). The functional properties of these robust microparticles can be easily varied by introducing various payloads, such as magnetic nanoparticles and/or fluorescent dyes, into the chitosan solution. The on-chip connection of such individual particles into well-defined microchains is demonstrated using GA again as the chemical "glue" and microchannel confinement as the spatial template. Chain flexibility can be tuned by adjusting the crosslinking conditions: both rigid chains and semiflexible chains are created. Additionally, the arrangement of particles within a chain can also be controlled, for example, to generate chains with alternating fluorescent and nonfluorescent microparticles. Such microassembled chains could find applications as microfluidic mixers, delivery vehicles, microscale sensors, or miniature biomimetic robots.

Microfluidic Fabrication of Bio-Inspired Microfibers with Controllable Magnetic Spindle-Knots for 3D Assembly and Water Collection

“…The diameters of the joint parts 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 13 constant magnetic field, each magnetic knot tends to establish an individual magnetic dipole aligned to the applied field, which provides a net torque to make the microfiber rotate until the direction of the microfibers is parallel with the rotating magnet bar. 49 show potential as mini/micro-mixers for local stirring and mixing.…”

Deformation of an elastic capsule in a rectangular microfluidic channel

“…In the area of interest of the present paper, the study of the motion and deformation of capsules and biological cells in microfluidic channels is motivated by a wide range of applications including drug delivery, cell sorting and cell characterization devices [1–3, 5, 7, 15, 27], fabrication of microcapsules with desirable properties [8, 17, 21, 26], determination of membrane properties [19, 24], microreactors with better mixing properties [4, 32], and of course its similarity to blood flow in vascular capillaries [22, 23]. …”

Tuning bubbly structures in microchannels

“…This can be accomplished by including an additional side channel. 41 Alternatively, the foam or emulsion could be compressed such that the effective length of the channel decreases by forcing the excess liquid out of the channel and causing the inclusions to deform and rearrange as necessary. 19 The bubble or droplet volume can also be controlled by the introduction of an automated system that would allow for a greater accessible range of bubble and droplet sizes, such as one that incorporates external valves.…”