**5. Nanofluidics**

**4.2. Postage stamp-sized microplasmas on polymeric substrates**

16 Microfluidics and Nanofluidics

To reduce ownership, operation and fabrication costs, we developed and evaluated a variety of microplasmas on polymeric substrates (e.g., **Figures 11** and **12**) [144–146]. Although a critical microplasma dimension was in μm-meter regime (**Figure 11**), these microplasmas were formed inside **millifluidic channels** (e.g., ~2 mm wide). This was done for rapid prototyping [109] and to avoid accidental contact of the microplasma with the channel-walls

**Figure 11.** (a) Postage stamp-sized polymeric 3D-chips and (b) microplasma formed between electrodes E1 and E2. Depending on operating conditions, microplasmas with diameters of (b) ~750 μm, (c) ~400 μm and (d) ~200 μm were

**Figure 12.** 3D printed microplasma on a hybrid 3D-chip formed between electrodes E1 and E2 (coin has been included

formed. A 1 cent coin was included for size, the microplasma fit inside the letter a of the coin.

for size, the microplasma fit inside the letter a of the 1 cent coin).

The nanoscale [157–194] is a natural extension of the microscale (**Figure 1**) and it is defined as the science, technology and application of transport phenomena and of fluid-flow in channels ≤100 nm or around nano-size objects [158, 170]. This is not universally accepted, many consider nano-size as anything with one critical dimension ≤1 μm. The range between 100 nm and 1 μm is sometimes referred to as *"extended nanofluidics"* [181]. Nanofluidics is not new, although the name is [159, 160].
