Microflotronics: A Flexible, Transparent, Pressure‐Sensitive Microfluidic Film

Abstract

There is an increasing demand for sensitive, flexible, and low‐cost pressure sensing solutions for health monitoring, wearable sensing, robotic and prosthetic applications. Here, the first flexible and pressure‐sensitive microfluidic film is reported, referred to as a microflotronic, with high transparency and seamless integratability with the state‐of‐the‐art microelectronics. The microflotronic film represents the initial effort to utilize a continuous microfluidic layer as the sensing elements for large‐area dynamic pressure mapping applications, and meanwhile an ultrahigh sensitivity of 0.45 kPa−1 has been achieved in a compact, flexible, and transparent packaging. The response time of the device is in the millisecond range, which is at least an order of magnitude faster than that of its conventional flexible solid‐state counterparts. In addition, the fabrication process of the device is fully compatible with the industrial‐scale manufacturing of capacitive touchscreen devices and liquid‐crystal displays. The overall device packaging can be as thin as 200 μm with an optical transparency greater than 80%. Several practical applications were successfully demonstrated, including surface topology mapping and dynamic blood pressure monitoring. The microflotronic devices offer an alternative approach to the solid‐state pressure sensors, by offering an unprecedented sensitivity and ultrafast response time in a completely transparent, flexible and adaptive platform.

Enhanced Sensitivity of Iontronic Graphene Tactile Sensors Facilitated by Spreading of Ionic Liquid Pinned on Graphene Grid

“…All the elements in the i‐GTS sensors are environmentally stable and mechanically flexible. The ionic liquid used in this experiment exhibits extremely low vapor pressure, indicating long‐term stability under ambient conditions, which is appropriate for an active element in a tactile sensor. In addition, no remaining ionic liquid satellites on the top electrode surface are detected after dynamic cyclic tests.…”

Ultrathin and Wearable Microtubular Epidermal Sensor for Real‐Time Physiological Pulse Monitoring

“…Taken as a whole, we observed that the sensor was very responsive to external pressures and demonstrated negligible electrical hysteresis. Indeed, unlike resistive nanocomposites that suffered from endemic low recovery and mechanical hysteresis, [51] our microtubular sensor responded to force changes within 5 ms at a frequency up to 75 Hz.…”

Monitoring of Vital Signs with Flexible and Wearable Medical Devices

“…[ 39,[70][71][72][73][74][75] These novel pressure sensors are typically in the form factor of capacitors, which use either a compressible dielectric to induce a change in capacitance or a piezoelectric dielectric to induce a voltage across the device. The signal from the capacitive elements are either amplifi ed by an external instrument or a monolithically integrated device on the same substrate, typically a thin fi lm transistor (TFT).…”

“…An addressable array of pressure sensors can be scanned to fi nd the pixel with the strongest pulse signal, as demonstrated by Li et al, avoiding the need to precisely place a wearable sensor. [ 71 ] Additionally, having an array of high-resolution sensors would make it possible to measure pulse delay between different locations, an important but infrequently used technique to assess cardiac health. [ 69 ] Despite the plethora of sensors demonstrated to measure the pulse pressure, few reports attempted to correlate the measured signals to blood pressure.…”