Integration of silicon chip microstructures for in-line microbial cell lysis in soft microfluidics

The paper presents fabrication methodologies that integrate silicon components into soft microfluidic devices to perform microbial cell lysis for biological applications. The integration methodology consists of a silicon chip that is fabricated with microstructure arrays and embedded in a microfluidic device, which is driven by piezoelectric actuation to perform cell lysis by physically breaking microbial cell walls via micromechanical impaction. We present different silicon microarray geometries, their fabrication techniques, integration of said micropatterned silicon impactor chips into microfluidic devices, and device operation and testing on synthetic microbeads and two yeast species (S. cerevisiae and C. albicans) to evaluate their efficacy. The generalized strategy developed for integration of the micropatterned silicon impactor chip into soft microfluidic devices can serve as an important process step for a new class of hybrid silicon-polymeric devices for future cellular processing applications. The proposed integration methodology can be scalable and integrated as an in-line cell lysis tool with existing microfluidics assays

Soft Microreactors for the Deposition of Conductive Metallic Traces on Planar, Embossed, and Curved Surfaces

Advanced manufacturing strategies have enabled large‐scale, economical, and efficient production of electronic components that are an integral part of various consumer products ranging from simple toys to intricate computing systems; however, the circuitry for these components is (by and large) produced via top‐down lithography and is thus limited to planar surfaces. The present work demonstrates the use of reconfigurable soft microreactors for the patterned deposition of conductive copper traces on flat and embossed two‐dimensional (2D) substrates as well as nonplanar substrates made from different commodity plastics. Using localized, flow‐assisted, low‐temperature, electroless copper deposition, conductive metallic traces are fabricated, which, when combined with various off‐the‐shelf electronic components, enabled the production of simple circuits and antennas with unique form factors. This solution‐phase approach to the patterned deposition of functional inorganic materials selectively on different polymeric components will provide relatively simple, inexpensive processing opportunities for the fabrication of 2D/nonplanar devices when compared to complicated manufacturing methods such as laser‐directed structuring. Further, this approach to the patterned metallization of different commodity plastics offers unique design opportunities applicable to the fabrication of planar and nonplanar electronic and interconnect devices, and other free‐form electronics with less structural “bloat” and weight (by directly coating support elements with circuitry)

Soft Microfluidic Reactors for the Deposition/Synthesis of Morphologically Controlled Inorganic Crystals

Hybrid or hierarchical nanomaterials with precisely controlled size, shape, and composition have potential applications in, for example, energy storage and conversion, photo-catalysis, and bio-sensing. While several strategies exist for the synthesis of hybrid or hierarchical structures, they are limited to the control of parameters such as, time, temperature, chemistry, and concentration. Strategies that take advantage of flow effects are relatively less explored, and present the opportunity to tune additional parameters (e.g., flow velocity and direction), providing higher levels of control in the bottom-up synthesis of nanomaterials. In the present work, the fabrication of soft, stretchable microfluidic systems via 3D printing and soft-lithography using elastomeric polymers, and their application to the controlled synthesis or deposition of inorganic materials is reported. The micro-reactors are reversibly sealed via compression or tension to various planar and non-planar substrates, and enable: (i) sequential synthesis or depositions, (ii) easy reuse of the reactors or substrates, and (iii) characterization of the device or substrate. Additionally, by tuning the compressive stress applied, the channel morphology and dimensions can be controlled. This phenomenon was further investigated using finite elemental analysis method (FEM) and experimental observations, and led to the fabrication of soft robotic systems with “programmable” transport properties that have integrated touch and actuation sensing. The soft micro-reactors were applied to: (i) synthesis of graded arrays of ZnO nanorods with spatial and compositional control through the rational control of the mass-transport phenomena, and (ii) the deposition of conductive copper traces on arbitrary substrates through a process referred to as microfluidic-directed electroless copper deposition (micro-DECD). The methods and insights emerging through these studies can be applied to the controlled synthesis and deposition of materials with diverse functional properties (e.g., optical, magnetic, electronic) with applications in the fields of micro-electronics, energy conversion, point-of-care diagnostics, etc. In addition to their synthetic applications, the bi-layered channel networks were also used in fabrication of a microfluidic system for infield sampling and analysis. Furthermore, the fabrication skills gained through this research were helpful in developing an educational and outreach activity that introduces soft robotics and general fabrication strategies such as 3D printing, soft lithography, replica molding, etc., to students as they build their own soft robot

Crystallization at Droplet Interfaces for the Fabrication of Geometrically Programmed Synthetic Magnetosomes

Many organisms rely on the precise growth, assembly, and/or organization of inorganic crystals to achieve vital functions, for example, three-dimensional structural support (i.e., skeletal systems based on calcite) or environmental sensing (i.e., magnetosomes based on magnetite). Mimicking the production of the complex products observed in these biomineralization processes, synthetically, remains challenging. Herein, a method for the synthesis of artificial magnetosomes with programmable magnetic domains was developed. Specifically, precursors were compartmentalized inside different surfactant-stabilized aqueous-phase droplets suspended in oil and microfluidic technologies were implemented to control their interactions precisely. When reactive droplets were brought into contact with one another, a lipid bilayer formed, allowing transport of reagents between droplets. This process led to interface-confined magnetite growth. These polarized magnetic domains were used to manipulate the synthetic magnetosomes using external magnetic fields, thus providing a convenient method for droplet manipulation and transport. This method of producing synthetic magnetosomes provides a route toward useful materials with applications in areas such as drug delivery and microfluidics

Reversible Mechanical Deformations of Soft Microchannel Networks for Sensing in Soft Robotic Systems

Microfluidics has enabled numerous applications in, for example, analytical chemistry, medical diagnostics, microelectronics, and soft robotics. In most of these applications, the geometries of the microchannels are of fixed dimensions that (ideally) remain invariant during operation. In soft robotics, however, the geometries of the microchannels contained in soft actuation systems are inherently dynamic, and the specific dimensions are expected to change during operation, and, by extension, the fluid transport properties of the system are variable. If this characteristic is not properly considered, or if methods are not developed to control it, the progress of soft robotic devices with distributed fluid transport systems can be hampered. Herein, the deformation of soft micro- channel networks is investigated using a finite-element method and experimental observations, and the understandings are applied to imbibe sensing capabilities in soft robots that have integrated microfluidic networks with dynamic channel geometries of predictable dimensions. This approach enables the fabrication of soft fluid transport systems with deterministic deformation characteristics—a capability that is specifically applied to touch and actuation sensing in soft actuators. This work provides insight into the channel deformation processes expected in soft robotic systems with embedded networks of microchannels, enabling devices with reliable/predictable transport properties