A flexible high-sensitivity piezoresistive sensor comprising a Au nanoribbon-coated polymer sponge

Abstract

Development of pressure sensors which display high sensitivity, and are flexible, inexpensive, and easy to manufacture has drawn significant interest due to their diverse applications such as tactile skin sensors (e.g.''electronic skin''), pulse detectors, speech recognition elements, and others. While varied technologies and molecular constructs have been demonstrated for pressure sensing, considerable conceptual and technical challenges still hamper broad implementation of many such systems. A novel flexible piezoresistive sensor comprising a conductive Au-coated elastomeric polymer sponge is presented. The piezoresistive sponge is prepared through a simple chemical route in which Au nanoribbons are spontaneously grown upon an aminefunctionalized polyurethane framework. The Au nanoribbon layer coats the internal surfaces within the polymer pore network, resulting in electrical current modulation upon pressure application/release through changes in the overall contact areas between the conductive surfaces. The Au-polyurethane piezoresistive sensor exhibits excellent functionalities, including enhanced sensitivity, low detection threshold, high fidelity, and physical stability. Application of the sensor is demonstrated for high resolution monitoring of wrist arterial pulses. Experimental section MaterialsHAuCl 4 Á3H 2 O, KSCN, branched polyethylenimine (b-PEI) with average M w B 25 000 by LS average M n B 10 000 by GPC, N-hydroxysuccinimide (NHS), 2-(N-morpholino)ethane sulfonic acid (MES) and

Silver Nanoflower Decorated Graphene Oxide Sponges for Highly Sensitive Variable Stiffness Stress Sensors

“…The strength could be controlled by changing the polymer concentration. Overall, the initial sensitivity (0.572 kPa −1 ) of the GO‐AgNF‐PI sponge was two times greater than the maximum value (0.31 kPa −1 ) of resistance‐type GO sponges in literature . The operating stress range (0–10 kPa) was wide that can be further expanded by changing the polymer concentration.…”

“…[2] In order to improve elasticity and strength, different types of polymers such as polydimethylsiloxane (PDMS), polyimide (PI), epoxy, and polyurethane (PU) were added to the 3D GO sponge structure. [2,[10][11][12][13][14] However, the addition of polymers caused a decrease in electrical conductivity. [14] The sensitivity, which is the normalized resistance change over pressure difference, was also low (maximum: 0.26 kPa −1 ) over a limited operation range when GO-polymer sponges were employed as resistance-type stress sensors in literature.…”

“…[14] The sensitivity, which is the normalized resistance change over pressure difference, was also low (maximum: 0.26 kPa −1 ) over a limited operation range when GO-polymer sponges were employed as resistance-type stress sensors in literature. [10][11][12][13]15] In order to enhance the electrical conductivity, platinum and silver nanoparticles were incorporated to the pure GO sponges. [16] These nanoparticles increased the electrical conductivity from 0.1 to 1 S m −1 (platinum) and 3.2 (silver) S m −1 .…”

“…The pure GO sponges are fragile and can be damaged under the applied stress . In order to improve elasticity and strength, different types of polymers such as polydimethylsiloxane (PDMS), polyimide (PI), epoxy, and polyurethane (PU) were added to the 3D GO sponge structure . However, the addition of polymers caused a decrease in electrical conductivity .…”

“…However, the addition of polymers caused a decrease in electrical conductivity . The sensitivity, which is the normalized resistance change over pressure difference, was also low (maximum: 0.26 kPa −1 ) over a limited operation range when GO‐polymer sponges were employed as resistance‐type stress sensors in literature …”