This disclosure provides microwell capsule array devices. The microwell capsule array devices are generally capable of performing one or more sample preparation operations. Such sample preparation operations may be used as a prelude to one more or more analysis operations. For example, a device of this disclosure can achieve physical partitioning and discrete mixing of samples with unique molecular identifiers within a single unit in preparation for various analysis operations. The device may be useful in a variety of applications and most notably nucleic-acid-based sequencing, detection and quantification of gene expression and single-cell analysis.