A new non-thermal method of altering the shape of cartilage to create mechanically stable new morphologies was developed using low DC voltage electric fields (electroforming). In cartilage electroforming, voltage is applied to the surfaces of cartilage specimens held in mechanical deformation by a jig made of two large surface area electrodes for 2-5 minutes. Following removal of the specimen from the jig, permanent shape change is observed. Electric resistance and mechanical stress were monitoring during electroforming. Strong correlation between resistance and stress was observed suggesting that the mechanism of stress relaxation is electrically mediated and may provide a mean to monitor electroforming.
Much interest has been placed on the permanent reshaping of cartilage for facial reconstructive surgery using lasers. An alternate way to reshape cartilage is to heat the tissue in a water bath while maintaining the specimen in mechanical deformation. The objective of this study was to measure the circular bend angle of a cartilage specimen produced by varying the temperature and immersion time in a water bath. Rectangular cartilage specimens (18 x 4 x 1.5 mm) were bent in a semicircular jig (diameter 11 mm) and then immersed in a saline bath at temperatures between 50 - 80°C. The immersion times were 5, 20, 80, 160 and 320 seconds at each temperature. The distance between the ends of each specimen was measured before reshaping and at 15 minutes and 24 hours after immersion in order to calculate the resulting bend angle. The largest bend angle occurred in the specimen immersed in saline at 74°C for 320 seconds, illustrating a definite thermal influence on the physical shape of the cartilage sample. The critical immersion times and bath temperatures where definite shape change occurred were determined.
Dielectric properties of cartilage have received comparatively little interest and few studies have examined the effect of the applying electric currents to mechanically deformed cartilages. The objective of this study was to determine the dependence of shape change on electrode composition during a process we have described as “electroforming.” Porcine nasal septal cartilage specimens (16 x 5 x 2 mm) were mechanically deformed between two semicircular electrodes. Direct current (DC) current was applied to establish charge separation and electrical streaming potential. Voltage (<10 V) and application time (0-6 minutes) were varied, and shape change was measured using analytic representation. Surface features were evaluated using light microscopy. While shape change strongly correlated with voltage and time for all electrode materials, the voltage and application time that produced maximum shape change (curvature of the jig, ~ 160°) varied for each material. Aluminum is more effective for electroforming than gold as it yields the lowest set of plateau values. Surface features indicated that electrodeposition occurs depending upon the voltage and the standard reduction potential of electrodes. The results from this study provide insight into the dependence of shape change on the external electrical environment of cartilage and how optimal shape change can be produced with nominal electrodeposition.