Electrohydrodynamic Processing of Micro- and Nanometer Biological Materials - Biomaterials Fabrication and Processing - page 275

11

Electrohydrodynamic
Processing of Micro- and
Nanometer Biological Materials

Yiquan Wu and Robert Lewis Clark

CONTENTS

11.1 Introduction ......................................................................................................................... 275
11.2 Electrospraying.................................................................................................................... 276
11.2.1 Defi nition ................................................................................................................ 276
11.2.2 Background............................................................................................................. 277
11.2.3 Mechanisms and Modes of Electrospraying........................................................... 279
11.2.4 Processing Parameters............................................................................................ 280
11.2.5 Theory Description and Modeling ......................................................................... 283
11.2.5.1 Physical Model of Liquid Cone Jet ......................................................... 283
11.2.5.2 Theory and Modeling of Jet Breakup ..................................................... 285
11.2.6 Basic Electrospraying System ................................................................................ 287
11.2.7 Characteristics of Electrospraying.......................................................................... 287
11.2.8 Fabrication of Biological Materials ........................................................................ 288
11.2.8.1 Drug Delivery Carriers ........................................................................... 288
11.2.8.2 Deposition of Bioactive Coatings and Films........................................... 297
11.2.8.3 Patterned Nanostructure Biomaterials .................................................... 308
11.2.8.4 Encapsulated Electrospraying of Biomaterials ....................................... 314
11.2.8.5 Aerosolization of Biomaterials ............................................................... 321
11.3 Summary ............................................................................................................................. 329
References ...................................................................................................................................... 330

11.1 INTRODUC TION
Electrohydrodynamic processing, in which a solution with a controlled fl ow rate is pumped into a
nozzle to initiate aerosol jets under an electric fi eld, is a novel and cost-effective technique capable
of producing particles in a range of micrometer to nanometer scales by altering the processing
parameters. Instead of using the inertial forces, a uniform electrohydrodynamic force is used to
break up the liquids into fi ne jets when the charge density on the droplet surface exceeds a critical
value known as the Rayleigh limit [1-4]. This process has recently attracted the attention of many
researchers, because this technique has been used to prepare both micro- and nanometer architec-
tures with application to patterned materials, bioactive fi lms and coatings, drug-delivery carriers,
and particles with controllable structures [5-10].
In a typical electrohydrodynamic process, a liquid precursor is fed through a nozzle and a
droplet forms at the nozzle. When a strong electric fi eld is applied over this droplet, a charge is
induced on the surface of the droplet. Infl uenced by the electrostatic fi eld, the droplet at the tip of
the nozzle forms a conical-shaped jet. When the electrostatic fi eld is suffi ciently strong, the charges

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