Graded-size microlens array by the pyro-electrohydrodynamic continuous printing method

Abstract

In the present work, the pyro-electrohydrodynamic technique was used for the realization of tunable-size microlens arrays. Poly(methyl methacrylate) dissolved in different solvent mixtures was used as the polymeric material for the realization of the microstructures. By controlling the experimental parameters and in particular, the volume of the drop reservoir, graded-size square arrays of tens of microlenses with focal length in the range 1.5-3 mm were produced. Moreover, the optical quality and geometrical features were investigated by profilometric and interferometric analysis.

Nanocomposite polymer carbon-black coating for triggering pyro-electrohydrodynamic inkjet printing

“…5 Regarding polymers handling, e.g., for the fabrication of optical components, EHD provides advantages in capabilities over conventional ink-jet approaches, but at the same time complex set-up including high-voltage generators, external electrodes, and additional micro components are needed. [15][16][17][18] Recently, an alternative technology, named pyro-EHD printing, [18][19][20][21][22] has been discovered. The pyro-EHD allows to manipulate liquids in a no-contact mode and avoids the use of nozzles and external electrodes, thus overcoming some severe limitations of ink-jet printing, like, for example, nozzle-clogging.…”

“…23 Even if the pyro-EHD approach adds important advantages in processing functional materials by simply applying a temperature gradient onto a pyro-electric crystal, some limitations are still encountered in printing small volumes of polymers at high resolution. 22 In fact, some polymers like polydimethylsiloxane (PDMS) and poly(methyl methacrylate) (PMMA), which are commonly employed in different fields of technology from electronic to biomicrofluidics, are very difficult to dispense even by pyro-EHD. Here, we propose an innovative method for the activation of the pyro-EHD inkjet system that allows the handling of very high viscous polymers and their direct printing.…”

Microlens Fabrication by Replica Molding of Electro-Hydrodynamic Printing Liquid Mold

“…Q is the flow rate, T is pulse width time, d is the duty ratio, and f is the pulse frequency. Therefore, deposited pattern diameter can be expressed as [27]…”

“…It enables the direct, additive patterning of materials with a resolution that can extend below 100 nm, and can print drop on demand. It has been applied to manufacture flexible electronics, sensors, transistors, microfluidic chip, and so on [22][23][24][25][26][27]. Therefore, it is promising to be used to manufacture sub-micron diameter microlens and microlens array molds quickly and cost-effectively.…”

Pyro-EHD ink-jet printing for direct functionalization of 3D lab-on-chip devices

“…Once a thermal gradient is applied it causes the pyroelectric effect, namely a change in P s as a function of temperature leading to an excess or lack of screening charges on the LN surface. Such uncompensated charge's density, ρ = Δ (P s -σ sc ), generates a high electric field as large as 10 6 -10 8 V/cm 19,20 . The relationship between the change in temperature and the change in spontaneous polarization is linear and can be written as ΔP i = p i ΔT, where P i is the coefficient of the polarization vector, p i is the pyroelectric coefficient (-4 × 10 -5 C/(m 2 K)), and ΔT is the temperature variation.…”