pipette aspiration

Module: solid

Category: load

Type string: "pipette aspiration"

Parameters

Name	Description	Default	Units
pressure	pressure	0	[P]
radius	Pipette radius	0	[L]
center	Pipette center	{0,0,0}	[L]
normal	Pipette normal	{0,0,1}	[]

Description

Pipette aspiration is a common tool in biomechanics: A pipette is pressed against a tissue surface (contact problem) and a known negative pressure is typically applied through the pipette to aspirate the tissue. Then, some relevant material property may be extracted from the observed aspirated height of the tissue under the prescribed pressure. This pressure load is similar to the pressure load described in Section Pressure-Load, however it must be used on a surface which is also the primary surface in a sliding-elastic contact interface. The contact interface must be between a circular pipette with inner radius R and the tissue. (In other words, the pipette has to be modeled explicitly in this contact analysis). The purpose of this pipette aspiration load is to prescribe the pressure only on the faces of the selected contact surface which happen to be inside the pipette footprint. Therefore, the pressure is not applied on the portion of the contact surface which has a non-zero contact pressure, or on the faces that fall outside of the pipette footprint.

This pressure load only works with circular pipettes. However, the pipette wall thickness is only modeled via the explicit representation of the pipette, and the pipette tip need not be flat (e.g., it could be semi-circular or beveled, etc.). The radius R represents the circular edge of the contact region in the absence of deformation (in the reference condition). The model may employ planes of symmetry, since those do not affect the specification of radius, center, or normal.