Parametric study of protein solution evaporation inside the microwells for micropatterning

In this study, evaporation of bovine serum albumin aqueous solution (BSA(aq)) inside microwells was investigated. A droplet of BSA(aq) was dispensed on a cleaned glass slide, followed by placing a polydimethylsiloxane (PDMS) stamp with microwell array on top of the droplet. Different deposited structures at micro/nano scale were obtained after complete evaporation of the solution. The operating parameters such as the dimensions of the microwells and solution concentrations were studied. It is found that, at lower solution concentration (e.g. 0.5–6 wt%), the ring structures were formed. As the solution concentration increased, part of the BSA molecules began to deposit inside the ring structures. The plateau-like structures were formed when the solution concentration exceeded 10 wt%. Meanwhile, more BSA molecules deposited outside the microwells to form the sedimentation layer. By taking the natural logarithm of the normalized height of the deposited structures and solution concentration, data points merged to form a master curve. It was also demonstrated that the deposited structures can be used as the mask for dry etching process. This method provides a relatively simple and reliable alternative for micro/nanopatterning.

► Evaporation of protein solution inside PDMS microwells is investigated and a phenomenological mechanism is proposed.
► The obtained structures are ring-like at lower solution concentration and plateau-like as the concentration exceeds 10 wt%.
► Master curve is acquired by taking logarithm plot of the height of the deposited structures versus solution concentration.
► The deposited protein structures can be used as the mask for ICP-RIE dry etching of silicon substrate.