on a control or comparison sample in some embodiments of the present invention the well 10 comprises at least one ligand or anti ligand in yet other embodiments the well 10 comprises reactive chemical groups grafted thereto techniques for grafting such groups on plastic are well known to those skilled in the art the well may also comprise a chromogen or a species which emits light or fluoresces under the conditions of the assay in a preferred embodiment of the present invention shown in fig1 4 the projections 20 extending upward from the well bottom 25 are pyramidal however the projections may be of any shape which will increase the surface area of the well 10 without creating areas that are hard to wash e g crevices and capillaries according to preferred embodiments of the present invention the projections are pyramidal columnar conical rectangular cylindrical or dome shaped the projections are spaced to form interconnecting channels therebetween to enable the sample and reagents to spread over the well bottom 25 devices according to the present invention offer advantages with respect to increased surface area for binding of the ligand or anti ligand and reproducibility it is desirable to increase the surface area of the well bottom 25 so as to maximize formation of reaction product such as in assays of substances.