Design, Fabrication, and Testing of a 3D Printer Based Microfluidic System

A pneumatically actuated PDMS based microfluidic devices were designed and fabricated by soft-lithography. Two types of molds were fabricated out of different material for this experiment. The first mold, (device 1), was fabricated from a sheet of Polymethyl methacrylate (PMMA) material, similar to Plexiglas. The device features were micro-engraved onto the face of the material. The second mold, (device 2), was fabricated from the use of fused deposition modeling (FDM) 3D printing. The pumping efficiency of the PDMS devices was analyzed through the characterization of the micro-pumps flowrate with respect to the pumps driving pressure and the actuation frequency. Tested at a driving pressure of 10psi, the flowrate for device 1 peaked at 75µL/min with a 7Hz actuation frequency before failing, while device 2 peaked at 498µL/min with a 15Hz actuation frequency. Using the techniques of rapid prototyping and fused deposition modelling a pneumatically actuated 3D printer based micro-pump and micro-mixer are fabricated. The devices were fabricated using a thermoplastic elastomer (TPE) material as an alternative material to the present polydimethylsiloxane (PDMS). The micro-pump’s fluid flow output was analyzed through the characterization of the micro-pumps flowrate with respect to the pumps driving pressure and the actuation frequency. Testing showed that a maximum flowrate of 1120µL/min was achieved at an actuation frequency of 10Hz with an applied driving pressure of 40psi. A qualitative mixing performance was conducted with the micro-mixer. The diffusion of two dyes was tested under an active mix and non-active mix condition. Testing showed that the active mixing condition resulted in a complete diffusion as opposed to the non-mixing condition which partially diffused. As a proof of concept for biological testing, E. coli and E.coli anti-bodies were mixes to measure the capturing efficiency. The results showed that the active mixing resulted in about 50% capturing efficiency as opposed to the non-mixing which resulted in 33% capturing efficiency

Implantable Microsystem Technologies For Nanoliter-Resolution Inner Ear Drug Delivery

Advances in protective and restorative biotherapies have created new opportunities to use site-directed, programmable drug delivery systems to treat auditory and vestibular disorders. Successful therapy development that leverages the transgenic, knock-in, and knock-out variants of mouse models of human disease requires advanced microsystems specifically designed to function with nanoliter precision and with system volumes suitable for implantation. The present work demonstrates a novel biocompatible, implantable, and scalable microsystem consisted of a thermal phase-change peristaltic micropump with wireless control and a refillable reservoir. The micropump is fabricated around a catheter microtubing (250 μm OD, 125 μm ID) that provided a biocompatible leak-free flow path while avoiding complicated microfluidic interconnects. Direct-write micro-scale printing technology was used to build the mechanical components of the pump around the microtubing directly on the back of a printed circuit board assembly. In vitro characterization results indicated nanoliter resolution control over the desired flow rates of 10–100 nL/min by changing the actuation frequency, with negligible deviations in presence of up to 10× greater than physiological backpressures and ±3°C ambient temperature variation. A biocompatibility study was performed to evaluate material suitability for chronic subcutaneous implantation and clinical translational development. A stand-alone, refillable, in-plane, scalable, and fully implantable microreservoir platform was designed and fabricated to be integrated with the micropump. The microreservoir consists two main components: a cavity for storing the drug and a septum for refilling. The cavity membrane is fabricated with thin Parylene-C layers, using a polyethylene glycol (PEG) sacrificial layer. The septum thickness is minimized by pre-compression down to 1 mm. The results of in vitro characterization indicated negligible restoring force for the optimized cavity membrane and thousands of punctures through the septum without leakage. The micropump and microreservoir were integrated into microsystems which were implanted in mice. The microtubing was implanted into the round window membrane niche for infusion of a known ototoxic compound (sodium salicylate) at 50 nL/min for 20 min. Real-time shifts in distortion product otoacoustic emission thresholds and amplitudes were measured during the infusion. The results match with syringe pump gold standard. For the first time a miniature and yet scalable microsystem for inner ear drug delivery was developed, enabling drug discovery opportunities and translation to human

Microfabrication Technology for Isolated Silicon Sidewall Electrodes and Heaters

This paper presents a novel microfabricationtechnology for highly doped silicon sidewall electrodesparallel to – and isolated from – the microchannel. Thesidewall electrodes can be utilised for both electricaland thermal actuation of sensor systems. Thetechnology is scalable to a wide range of channelgeometries, simplifies the release etch, and allows forfurther integration with other Surface ChannelTechnology-based systems. Furthermore, thefabrication technology is demonstrated through thefabrication of a relative permittivity sensor. The sensormeasures relative permittivity values ranging from 1 to80, within 3% accuracy of full scale, including waterand water-containing mixtures

Velocity-independent thermal conductivity and volumetric heat capacity measurement of binary gas mixtures

In this paper, we present a single hot wire suspended over a V-groove cavity that is used to measure the thermal conductivity ($k$) and volumetric heat capacity ($\rho c_p$) for both pure gases and binary gas mixtures through DC and AC excitation, respectively. The working principle and measurement results are discussed

3D Printed Microfluidic Devices

3D printing has revolutionized the microfabrication prototyping workflow over the past few years. With the recent improvements in 3D printing technologies, highly complex microfluidic devices can be fabricated via single-step, rapid, and cost-effective protocols as a promising alternative to the time consuming, costly and sophisticated traditional cleanroom fabrication. Microfluidic devices have enabled a wide range of biochemical and clinical applications, such as cancer screening, micro-physiological system engineering, high-throughput drug testing, and point-of-care diagnostics. Using 3D printing fabrication technologies, alteration of the design features is significantly easier than traditional fabrication, enabling agile iterative design and facilitating rapid prototyping. This can make microfluidic technology more accessible to researchers in various fields and accelerates innovation in the field of microfluidics. Accordingly, this Special Issue seeks to showcase research papers, short communications, and review articles that focus on novel methodological developments in 3D printing and its use for various biochemical and biomedical applications

Microfluidics for Biosensing

There are 12 papers published with 8 research articles, 3 review articles and 1 perspective. The topics cover: Biomedical microfluidics Lab-on-a-chip Miniaturized systems for chemistry and life science (MicroTAS) Biosensor development and characteristics Imaging and other detection technologies Imaging and signal processing Point-of-care testing microdevices Food and water quality testing and control We hope this collection could promote the development of microfluidics and point-of-care testing (POCT) devices for biosensing