Development of a skin-adapted absorbent core for adult-type briefs. A: Illustration of a generic diaper design. AC corresponds to the absorbent core, SP corresponds to the side panels. Side panels can be made from plastic films (including micro-perforated films) which are virtually impervious to air or from nonwovens with extremely high air-permeability characteristics. B: Schematic illustration of a "skin-adapted" incontinence brief design. 1 - corresponds to the top sheet which is in direct contact with the skin; 2 - curled fiber cellulose layer; 3 - standard cellulose fluff containing superabsorbent polymers; 4 - cellulose distribution layer to facilitate fluid distribution and the utilization of superabsorbent polymers which did not have had direct initial contact with fluid/urine; 5 - outer sheet. C: pH gradient within the skin-adapted product design. A colored pH indicator clearly demonstrates the gradient inside the product. Within minutes after wetting the curled fiber layer stains intensively red indicating an acidic environment on the skin facing surface (left picture). Inside the brief the superabsorbent polymer-containing fluff stains yellow to green (middle picture) which indicates a pH where the superabsorbent polymer has its absorption optimum. This internal gradient is stable for several hours. Red corresponds to pH values around 4.0, yellow to a pH around 6.0, green to a pH around 7.0 (right picture). D: Surface pH measurements after repeated loading of the incontinence brief. 500 ml 0.9% NaCl solution (urine replacement solution) with a starting pH of 6.8 were rapidly applied (within 30 seconds) to the absorption core of the briefs. pH measurements were taken after 1, 3, 5, 10, 15 and 20 minutes. To simulate multiple micturition, the brief was left untouched and loaded with 200 ml of the fluid after 120 minutes and after 300 min. Time of pH value readings are indicated on the x-axis, the y-axis indicates the pH value. Black squares correspond to the surface pH of the skin-adapted incontinence brief design; black circles correspond to the conventional design of incontinence briefs. The experiments were done in triplicates in two independent series.