title: Apparatus for measuring the finite load-deformation behavior of a sheet of epithelial cells cultured on a mesoscopic freestanding elastomer membrane.
abstract: Details are given for the design, calibration, and operation of an apparatus for measuring the finite load-deformation behavior of a sheet of living epithelial cells cultured on a mesoscopic freestanding elastomer membrane, 10 microm thick and 5 mm in diameter. Although similar in concept to bulge tests used to investigate the mechanical properties of micromachined thin films, cell-elastomer composite diaphragm inflation tests pose a unique set of experimental challenges. Composite diaphragm (CD) specimens are extremely compliant (E<50 kPa), experience large displacements when subject to small inflation pressures (approximately 100 Pa), and must be continuously immersed in a bath of liquid culture medium during the acquisition of load-deformation measurements. Given these considerations, we have constructed an inflation apparatus consisting of an air-piston-cylinder pump integrated with a modular specimen mounting fixture that constitutes a horizontally semi-infinite reservoir of liquid culture medium. In a deformation-controlled inflation test, pressurized air is used to inflate a CD specimen into the liquid reservoir with minimum disturbance of the liquid-air interface. Piston displacements and absolute pump chamber air pressures are utilized as feedback to cycle the displaced (or inflated) CD volume V in a 0.05 Hz triangular or sinusoidal wave form (V(MIN)=0 microl, V(MAX)<or=40 microl) while simultaneously recording the inflation pressure acting at the fixed boundary of the specimen, p(r=a). Using a carefully prescribed six-cycle inflation test protocol, the apparatus is shown to be capable of measuring the [V, p(r=a)] inflation response of a cell-elastomer CD with random uncertainties estimated at +/-0.45 microl and +/-2.5 Pa, respectively.
authors: Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 West Green Street, Urbana, Illinois 61801, USA.
authors: John C
authors: JC
authors: Selby
authors: Mark A
authors: MA
authors: Shannon
mesh_terms: D001696:Biomechanical Phenomena / Q000295:instrumentation*; D002478:Cells, Cultured; D004548:Elasticity; D020724:Elastomers / Q000737:chemistry*; D004847:Epithelial Cells; D006801:Humans; D015603:Keratinocytes; D008567:Membranes, Artificial
chemical_list: D020724:Elastomers; D008567:Membranes, Artificial