Marc Madou

A Computer-Controlled Near-Field Electrospinning Setup and Its Graphic User Interface for Precision Patterning of Functional Nanofibers on 2D and 3D Substrates

Electrospinning is a versatile technique for production of nanofibers. However, it lacks the precision and control necessary for fabrication of nanofiber-based devices. The positional control of the nanofiber placement can be dramatically improved using low-voltage near-field electrospinning (LV-NFES). LV-NFES allows nanofibers to be patterned on 2D and 3D substrates. However, use of NFES requires low working distance between the electrospinning nozzle and substrate, manual jet initiation, and precise substrate movement to control fiber deposition. Environmental factors such as humidity also need to be controlled. We developed a computer-controlled automation strategy for LV-NFES to improve performance and reliability. With this setup, the user is able to control the relevant sensor and actuator parameters through a custom graphic user interface application programmed on the C#.NET platform. The stage movement can be programmed as to achieve any desired nanofiber pattern and thickness. The nanofiber generation step is initiated through a software-controlled linear actuator. Parameter setting files can be saved into an Excel sheet and can be used subsequently in running multiple experiments. Each experiment is automatically video recorded and stamped with the pertinent real-time parameters. Humidity is controlled with ±3% accuracy through a feedback loop. Further improvements, such as real-time droplet size control for feed rate regulation are in progress.

An application specific multi-channel stimulator for electrokinetically-driven microfluidic devices

This paper presents a sixteen-channel sinusoidal generator with independent control of frequency and amplitude for each channel. This generator has application as stimulator of microfluidic devices that use electrokinetic forces for particle manipulation. The stimulator is based on a CMOS application specific circuit and an interface card. Several generator techniques were compared based on frequency range, total harmonic distortion (THD), and on-chip required area. The selected approach is based in a triangle-to-sine converter and presents a frequency range of 8kHz to 21MHz, an output voltage range of 0V to 3.1VPP, and a maximum THD of 5.11%. The device, fabricated in a 0.35μm CMOS technology, has a footprint of 1560μm×2030μm. Additional electronics in the interface card extends the frequency and voltage ranges to 50Hz-21MHz and 0–20VPP. The generator functionality was tested by implementing an experimental set-up where particle trapping was performed. The experimental set-up consisted of a micromachined channel with embedded electrodes configured as two electrical ports located at different positions along the channel. By choosing specific amplitude and frequency values from the generator, different particles suspended in a fluid were simultaneously trapped at different ports. The multichannel stimulator presented here can be used in many other microfluidic experiments and devices focused on particle trapping, separation and characterization.