Characterization of Electrospinning Fiber Diameter Distributions and Process Dynamics for Development of Real-Time Contr
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0948-B07-02
Characterization of Electrospinning Fiber Diameter Distributions and Process Dynamics for Development of Real-Time Control Xuri Yan1, Michael Gevelber1, Jian Yu2, and Gregory Rutledge2 1 Boston University, Brookline, MA, 02446 2 MIT, Cambridge, MA, 02139 ABSTRACT An integrated data acquisition/actuator control system is developed to conduct experiments investigating the fundamental dynamics for different operating conditions in an electrospinning system. The relation between measured variables (fiber current, whipping angle, jet length, and expulsion cone volume) to the resulting fiber diameter distribution is analyzed. INTRODUCTION In many emerging electrospinning applications, the fiber diameter distribution has important implications for yield, material utilization, and production rate. This paper reports our results on analyzing the relation between the operating point, the dynamics of electrospinning process, and the resulting diameter distributions. EXPERIMENTAL MEASUREMENT SYSTEM AND APPROACH The electrospinning system consists of a syringe needle (1 mm ID), high voltage power supply (Gamma High Volt. Res. XRM30P), syringe pump (Harvard PHD 2000), set up in a plexiglass enclosure with a grounded plate of variable offset distance (35 cm. nominal). A computer based data acquisition and actuator control system is used to map the operating conditions for achieving different expulsion cone-jet shapes for several Polyethylene oxide (PEO, Aldrich, 4×105 average molecular weight) concentrations in distilled water. Figure 1 is a schematic of the measurement system [1], including a vision system which measures at a 5 Hz rate the variations in the upper cone-jet volume, ∀ cone, the upper jet diameter, duj, the length of the straight jet, Luj, and the angle θ of the whipping region. In addition, the current conducted to the plate is measured and recorded at the same time, If. Figure 2 shows an image of A the upper cone of the expulsion area (left), B an individual fiber at the start of the whipping region (center), and C an image obtained with longer exposure time used to obtain the whipping region angle (right). The computer system also controls the solution flow rate, Qpump, and the applied voltage, E, which makes it easy to set the operating conditions in response to the observed variables. To conduct the experiments, the voltage is varied for a desired flow rate until a desired expulsion volume is observed. The computer acquisition/control system, with a user interface that display’s real time images and values of the measurement variables, enables rapid determination of operating conditions to perform a desired experiment.
Qpump E: voltage
∀ cone
Luj
C
θ
duj
θ: angle
A
A
B
Figure 2. Real-time image of electrospinning process A). Expulsion Taylor cone B). Individual fiber C). Whipping angle θ
If: current
Figure 1. Measured parameters for electrospinning system.
The vision system is implemented with 3 CMOS cameras (Basler A602f), with appropriate lens to resolve both the upper jet area and
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