A sample-to-result ddPCR platform based on a microfluidic chip with a dual-function flow-focusing structure enabling droplet generation via forward flow and droplet readout via reflux by rotating the rotary valve was developed.

Indium tin oxide (ITO) is a functional material with great transparency, machinability, electrical conductivity and thermo–sensitivity. Based on its excellent thermoelectric performance, we designed and fabricated a multilayer transparent microfluidic chip with multiple sets of on–chip heating, local temperature measurement and positive on–chip cooling function units. Temperature control plays a significant role in microfluidic approaches, especially in the devices that are designed for bioengineering, chemical synthesis and disease detection. The transparency of the chip contributes to achieve the real–time observation of fluid flow and optical detection. The chip consists of a temperature control layer made with an etched ITO deposited glass, a PDMS (polydimethylsiloxane) fluid layer, a PDMS cooling and flow control layer. The performances of the ITO on–chip microheaters, ITO on–chip temperature sensors and two coolants were tested and analyzed in different working conditions. The positive on–chip heating and cooling were proved to be area-specific under a large temperature–regulating range. This PDMS–ITO–glass based chip could be applied to both temporal and spatial stable temperature–regulating principles for various purposes.

In regular biosample cryopreservation operations, dropwise pipetting and continuous swirling are ordinarily needed to prevent cell damage (e.g. sudden osmotic change, toxicity and dissolution heat) caused by the high-concentration cryoprotectant (CPA) addition process. The following CPA removal process after freezing and rewarming also requires multiple sample transfer processes and manual work. In order to optimize the cryopreservation process, especially for trace sample preservation, here we present a microfluidic approach integrating CPA addition, sample storage, CPA removal and sample resuspension processes on a 30 × 30 × 4 mm³ three-layer chip. The sample solution could be added into CPA solution with pre-generated increasing concentration to decrease possible osmotic damage. Utilizing specially designed microfluidic structure and fluid field analysis, on-chip sample enrichment and CPA removal were achieved. A novel dead-end micro valve strategy with a simplified control module was applied and evaluated to assist on-chip mixing and sample pellet resuspension. The entire biosample cryopreservation process was also performed that verified the functions of the integrated microfluidic platform. Altogether, this developed platform could be an effective approach to realize automatic, all-in-one, low-damage cryopreservation operation.