A simple and reliable microfabrication process for a programmable microvalve array.

We describe our reliable methodology for fabricating a complex programmable microvalve array (PMA) and its integration with a glass microcapillary electrophoresis chip. This methodology is applicable to any device that requires multilayered PDMS, multiple alignment processes, selective PDMS bonding, and multilayered integration with downstream sensing systems. Along with the detailed step-by-step process, we discuss essential quality assurance checks that can be performed throughout fabrication to assist in troubleshooting and maximizing chip yield.•Comprehensive instructions for designing and fabricating a programmable microvalve array.•Selective bonding of PDMS and glass by microcontact printing.•Numerous quality control procedures to boost chip yield.

Digital microfluidics using a differentially polarized interface (DPI) to enhance translational force.

Direct current (DC)-digital microfluidics (DMF) enables the manipulation of droplets to revolutionize medical diagnostics, environmental assays, and fundamental biology. However, DC-DMF requires high voltages to generate droplet motion, which often breaks dielectric layers at the micro/nano scale, causing electrolysis. To minimize these issues, oil-fillers are commonly used to decrease the voltage requirement by reducing the surface tension of the droplet to the surrounding fluid. However, these oil-fillers increase DC-DMF complexity and decrease versatility. In this study, by adapting a differentially polarized interface (DPI) to generate an effective electromechanical force, the voltage required to manipulate a droplet was reduced from 600 V to 85 V without an oil-filler or special dielectric materials. By analyzing the temporal profiles of the contact angles during droplet motion under this DPI condition, this study, for the first time, distinguished the contributions of electrowetting and electromechanical forces to the translational movement of droplets. Dominant contribution of electrowetting is observed at the initial stage of the droplet translation with 52.8% reduction in the advancing contact angle and 20% reduction in the receding contact angle. However, after saturation in the temporal change of the contact angle, the effect of electrowetting contribution gradually decreases and electromechanical forces predominate. DPI-based digital microfluidics reduces the overall cost and complexity of stand-alone DC-DMF platforms, enabling filler-less and low-voltage applications for manipulating a wide range of liquid samples.

Feasibility of Detecting Bioorganic Compounds in Enceladus Plumes with the Enceladus Organic Analyzer.

Enceladus presents an excellent opportunity to detect organic molecules that are relevant for habitability as well as bioorganic molecules that provide evidence for extraterrestrial life because Enceladus' plume is composed of material from the subsurface ocean that has a high habitability potential and significant organic content. A primary challenge is to send instruments to Enceladus that can efficiently sample organic molecules in the plume and analyze for the most relevant molecules with the necessary detection limits. To this end, we present the scientific feasibility and engineering design of the Enceladus Organic Analyzer (EOA) that uses a microfluidic capillary electrophoresis system to provide sensitive detection of a wide range of relevant organic molecules, including amines, amino acids, and carboxylic acids, with ppm plume-detection limits (100 pM limits of detection). Importantly, the design of a capture plate that effectively gathers plume ice particles at encounter velocities from 200 m/s to 5 km/s is described, and the ice particle impact is modeled to demonstrate that material will be efficiently captured without organic decomposition. While the EOA can also operate on a landed mission, the relative technical ease of a fly-by mission to Enceladus, the possibility to nondestructively capture pristine samples from deep within the Enceladus ocean, plus the high sensitivity of the EOA instrument for molecules of bioorganic relevance for life detection argue for the inclusion of EOA on Enceladus missions. Key Words: Lab-on-a-chip-Organic biomarkers-Life detection-Planetary exploration. Astrobiology 17, 902-912.

A fully automated microfluidic micellar electrokinetic chromatography analyzer for organic compound detection.

An integrated microfluidic chemical analyzer utilizing micellar electrokinetic chromatography (MEKC) is developed using a pneumatically actuated Lifting-Gate microvalve array and a capillary zone electrophoresis (CZE) chip. Each of the necessary liquid handling processes such as metering, mixing, transferring, and washing steps are performed autonomously by the microvalve array. In addition, a method is presented for automated washing of the high resistance CZE channel for device reuse and periodic automated in situ analyses. To demonstrate the functionality of this MEKC platform, amino acids and thiols are labeled and efficiently separated via a fully automated program. Reproducibility of the automated programs for sample labeling and periodic in situ MEKC analysis was tested and found to be equivalent to conventional sample processing techniques for capillary electrophoresis analysis. This platform enables simple, portable, and automated chemical compound analysis which can be used in challenging environments.

Fabrication of PDMS Nanocomposite Materials and Nanostructures for Biomedical Nanosystems.

Recent applications of PDMS nanocomposite materials and nanostructures have dramatically increased in biomedical fields due to optical, mechanical and electrical properties that are controllable by nanoengineering fabrication processes. These applications include biomedical imaging, biosensing, and cellular bioengineering studies using PDMS engineered structures with nanoparticles, nanopillars and functional nanoporous membranes. This article reviews the recent progress of PDMS nanocomposite materials and nanostructures and provides descriptions of various fabrication techniques. Together with these fabrication techniques, we discuss how these nanocomposite PDMS biomedical devices are revolutionizing biomedical science and engineering fields.

Biomimetic cardiac microsystems for pathophysiological studies and drug screens.

Microfabricated organs-on-chips consist of tissue-engineered 3D in vitro models, which rely on engineering design and provide the physiological context of human organs. Recently, significant effort has been devoted to the creation of a biomimetic cardiac system by using microfabrication techniques. By applying allometric scaling laws, microengineered cardiac systems simulating arterial flow, pulse properties, and architectural environments have been implemented, allowing high-throughput pathophysiological experiments and drug screens. In this review, we illustrate the recent trends in cardiac microsystems with emphasis on cardiac pumping and valving functions. We report problems and solutions brought to light by existing organs-on-chip models and discuss future directions of the field. We also describe the needs and desired design features that will enable the control of mechanical, electrical, and chemical environments to generate functional in vitro cardiac disease models.