Figure 4

Liquid-state physical sensing platforms. (a) Ionic liquid-based electrofluidic pressure sensor. Schematic illustration depicting the device architecture of the pressure sensor and optical image showing the as-fabricated device. The top electrofluidic circuit and the bottom microfluidic channel were filled with blue and red dyes, respectively. Adapted with permission from Ref. 41. Copyright 2011 The Royal Society of Chemistry. (b) Hybrid soft strain sensor. Optical image showing the as-fabricated sensor with its stretchability and bendability. Adapted with permission from Ref. 42. Copyright 2013 IEEE. (c) Metallic liquid-based microfluidic pressure sensor. Optical image showing the as-fabricated microfluidic pressure sensor with its channel features and dimensions. Adapted with permission from Ref. 43. Copyright 2015 MDPI AG. (d) Iontronic microdroplet array (IMA) flexible tactile sensor. Optical image illustrating the fully fabricated IMA tactile sensor array consisting of 12×12 elements. Adapted with permission from Ref. 105. Copyright 2014 The Royal Society of Chemistry. (e) Microfluidics-based three-dimensional tactile force sensor. Optical image showing the actual fabricated microfluidic tactile sensing devices for three-dimensional force measurements. Scale bar 2 mm. Inset shows the device architecture of the microfluidics-based three-dimensional tactile force sensor. Adapted with permission from Ref. 106. Copyright 2014 The Royal Society of Chemistry. (f) Liquid-state heterojunction sensor. Optical image depicting the actual fabricated liquid-state heterojunction sensor. Scale bar 2.5 mm. Adapted with permission from Ref. 102. Copyright 2014 Macmillan Publishers Limited. (g) Graphene oxide (GO) nanosuspension liquid-state microfluidic tactile sensing device. Optical image showing the fully fabricated liquid-state tactile sensor with its distinctive features. Adapted with permission from Ref. 107. Copyright 2016 Wiley-VCH Verlag GmbH & Co.