Point-of-use robotic sensors for simultaneous pressure detection and chemical analysis

Abstract

The development of sensors for monitoring hazardous materials in security and environmental applications has been increasing in the last few years. In particular, organophosphates pose a serious health threat that affects the food and agriculture industries. Hence, their rapid on-site detection is highly desired, especially through remote robotic sampling that can minimize the exposure of humans to these hazardous chemicals. To handle sample collection, a robotic manipulator requires tactile feedback, to ensure that no damage will be done to either the robot or the other object in contact due to excessive force. To provide tactile feedback, porous polydimethylsiloxane pressure sensors based on a capacitive mechanism were chosen here, and integrated with enzyme-based electrochemical sensors specific for organophosphate compounds (e.g. methyl paraoxon). This results in a hybrid physical–chemical sensing glove that can simultaneously measure the pressure and chemical target without interference between the two sensors. Our pressure sensors showed >55% relative capacitance change per 10 kPa applied pressure, with an average sensitivity (S) of 0.057 ± 0.004 kPa⁻¹ in the 3–20 kPa range and a maximum sensitivity of 0.30 ± 0.08 kPa⁻¹ in the <0.05 kPa range. The chemical biosensors showed a detection range of 20–180 μM for methyl paraoxon in the liquid phase. We have thus combined low-cost chemical and pressure sensors together on disposable, retrofitting gloves, and demonstrated simultaneous tactile sensing and organophosphate pesticide detection in a point-of-use robotic field platform that is scalable, economical, and adaptable for different security, environmental, and food-safety applications.