The efficacy of traditional chemotherapy often suffers from rapid clearance and off-target toxicity. Drug delivery systems and controlled release are applied to improve the therapeutic efficiencies of small-molecule drugs. In this work, two novel oxidative/reductive (Ox/Re) -sensitive and one non-sensitive Paclitaxel (PTX) prodrugs were synthesized with a maleimide group, which rapidly conjugates with albumin in vivo. Albumin serves as a good vehicle to deliver more prodrug to tumors due to the enhanced permeation and retention (EPR) effect. PTX was then released from the prodrugs in glutathione(GSH)/ reactive oxygen species(ROS)-rich tumor microenvironments. This bioresponsive prodrug strategy demonstrates potent chemotherapeutic efficiency in vivo and may be utilized in clinical cancer therapy.

In this paper, we propose a novel tactile sensor with a “fingerprint” design, named due to its spiral shape and dimensions of 3.80 mm × 3.80 mm. The sensor is duplicated in a four-by-four array containing 16 tactile sensors to form a “SkinCell” pad of approximately 45 mm by 29 mm. The SkinCell was fabricated using a custom-built microfabrication platform called the NeXus which contains additive deposition tools and several robotic systems. We used the NeXus’ six-degrees-of-freedom robotic platform with two different inkjet printers to deposit a conductive silver ink sensor electrode as well as the organic piezoresistive polymer PEDOT:PSS-Poly (3,4-ethylene dioxythiophene)-poly(styrene sulfonate) of our tactile sensor. Printing deposition profiles of 100-micron- and 250-micron-thick layers were measured using microscopy. The resulting structure was sintered in an oven and laminated. The lamination consisted of two different sensor sheets placed back-to-back to create a half-Wheatstone-bridge configuration, doubling the sensitivity and accomplishing temperature compensation. The resulting sensor array was then sandwiched between two layers of silicone elastomer that had protrusions and inner cavities to concentrate stresses and strains and increase the detection resolution. Furthermore, the tactile sensor was characterized under static and dynamic force loading. Over 180,000 cycles of indentation were conducted to establish its durability and repeatability. The results demonstrate that the SkinCell has an average spatial resolution of 0.827 mm, an average sensitivity of 0.328 $\mathsf{m}\mathsf{\Omega }/\mathsf{\Omega }/\mathsf{N}$, expressed as the change in resistance per force in Newtons, an average sensitivity of 1.795 µV/N at a loading pressure of 2.365 PSI, and a dynamic response time constant of 63 ms which make it suitable for both large area skins and fingertip human–robot interaction applications.

In this paper, we present the design, fabrication, integration, and performance evaluation of SkinCell sensors, a novel tactile array targeting human-robot interaction applications. A polyimide sheet is selected as the substrate of the sensor, and gold electrodes with circular inter-digitated finger patterns are deposited through DC sputtering, creating a 4 by 4 sensor array with 16 tactile elements. Sensing elements are completed with a thin layer of spin coated PEDOT:PSS organic polymer solution. Two individual sensor sheets are being laminated in a back-to-back fashion to create a half-Wheatstone-bridge configuration to reduce temperature coupling while improving sensitivity. The sensor array is then sandwiched between two layers of silicone elastomer with internal dimples and cavities to improve sensitivity, repeatability, and center of force detection resolution. A COMSOL® simulation was performed to study the influence of adding the silicone encapsulation as well as design parameters to the sensor substrate. Our simulation results indicate an effective improvement of touch – voltage sensitivity by employing the featured encapsulation. Characterization experiments have been conducted to identify the sensitivity profile of each sensor on the array, which indicates an average sensitivity of 26.5μV/N. In subsequent experiments, the calibration profiles are used to identify the resultant force during pressing, as well as the location of the center of pressure on the SkinCell sensor. Finally, SkinCell sensors have been integrated into the OctoCan, a structural electronic device that can acquire squeezing pressure data during physical human-robot interaction.

Inkjet printing for fabricating microstructures has gained popularity during the last decade, making it possible to realize complex electronic circuits, components, and devices previously manufactured using 2D lithographic processes. Aerosol jet printing enables the deposition of feature sizes in the micron-scale order. Investigated in this work, is a tactile sensor featuring a strain gauge in a circular pattern and using aerosol inkjet printing delivered from the NeXus, a custom-built microfabrication platform that can deposit silver ink on a flexible printed circuit (FPC) substrate. Also presented is the finite element analysis (FEA) to evaluate the performance of the tactile sensor, packaged in between cover and bedding created with elastomer to fit the tactile sensor. The elastomer covering and bedding contains a dimple and cavity complying with external deformation, which concentrates the applied indented force. Simulation was used to optimize the configuration of the dimple size, cover, and bedding design required to improve the sensor performance. The fabrication method for creating 10mm diameter circular strain gauge tactile sensors include an annealing process using the oven, developed by comparing different curing time. Finally, experimental indentation tests were carried out under varying curing schedules, evaluated by loading packaged sensors with increasing weight, and indented force profile from 0.5-2.0N. Results show a 67% decrease in resistance from 2-20 hours of oven cure and about a 0.08% increase in sensitivity.