Four degree of freedom liquid dispenser for direct write capillary self-assembly with sub-nanoliter precision

Abstract

Capillary forces provide a ubiquitous means of organizing micro- and nanoscale structures on substrates. In order to investigate the mechanism of capillary self-assembly and to fabricate complex ordered structures, precise control of the meniscus shape is needed. We present a precision instrument that enables deposition of liquid droplets spanning from 2 nl to 300 μl, in concert with mechanical manipulation of the liquid-substrate interface with four degrees of freedom. The substrate has sub-100 nm positioning resolution in three axes of translation, and its temperature is controlled using thermoelectric modules. The capillary tip can rotate about the vertical axis while simultaneously dispensing liquid onto the substrate. Liquid is displaced using a custom bidirectional diaphragm pump, in which an elastic membrane is hydraulically actuated by a stainless steel syringe. The syringe is driven by a piezoelectric actuator, enabling nanoliter volume and rate control. A quantitative model of the liquid dispenser is verified experimentally, and suggests that compressibility in the hydraulic line deamplifies the syringe stroke, enabling sub-nanoliter resolution control of liquid displacement at the capillary tip. We use this system to contact-print water and oil droplets by mechanical manipulation of a liquid bridge between the capillary and the substrate. Finally, we study the effect of droplet volume and substrate temperature on the evaporative self-assembly of monodisperse polymer microspheres from sessile droplets, and demonstrate the formation of 3D chiral assemblies of micro-rods by rotation of the capillary tip during evaporative assembly.

Straight-Line Mechanisms as One Building Element of Small Precise Robotic Devices

“…When is talked about gripping of small object is one important requirement connected by moving of fingers. Many tasks require that movement of finger of gripper will be moving parallelly with all gripper's fingers [14,15], in case of planar devices it mean movement of two fingers. But parallel movement of some fingers is possible to gain only by utilization of straight-line structure in structure of whole gripper.…”

A predictive thermal dynamic model for parameter generation in the laser assisted direct write process

“…Flow-based DW requires high precision micro-dispensing technology which could be in the form of a precise pneumatic pump or an extrusion process. A precision instrument that enables deposition of liquid droplets spanning from 2 nano litre to 300 micro litre has been developed utilizing piezoelectric actuators for volume control [36][37][38][39][40]. The material delivered is through a very small orifice of a needle, restricting the size of the particles that can populate a composite ink.…”

Direct-Write Self-Assembly of 3d Colloidal Microstructures

“…Figure 1: (a) Liquid dispensing system (adapted from [3]); (b) schematic of 4-DOF motion control, and (c) schematic of directwrite assembly process.…”

“…To facilitate this study, we designed and built a precision instrument (Fig. 1a, [3]), which can simultaneously deposit and manipulate nano-and microliter liquid droplets on a temperature controlled substrate, in four degrees of freedom (Fig. 1b).…”