Finding a low-cost and effective method at low temperatures for producing reduced graphene oxide (rGO) has been the focus of many efforts in the research community for almost two decades. Overall, rGO is a promising candidate for use in supercapacitors, batteries, biosensors, photovoltaic devices, corrosion inhibitors, and optical devices. Herein, we report the formation of rGO from two electrically insulating polymers, polytetrafluoroethylene (PTFE) and meta-polybenzimidazole fiber (m-PBI), using an excimer pulsed laser annealing (PLA) method. The results from X-ray diffraction, scanning electron microscopy, electron backscattered diffraction, Raman spectroscopy, and Fourier-transform infrared spectroscopy confirm the successful generation of rGO with the formation of a multilayered structure. We investigated the mechanisms for the transformation of PTFE and PBI into rGO. The PTFE transition occurs by both a photochemical mechanism and a photothermal mechanism. The transition of PBI is dominated by a photo-oxidation mechanism and stepwise thermal degradation. After degradation and degassing procedures, both the polymers leave behind free molten carbon with some oxygen and hydrogen content. The free molten carbon undergoes an undercooling process with a regrowth velocity (<4 m·s⁻¹) that is necessary for the formation of rGO structures. This approach has the potential for use in creating future selective polymer-written electronics.

Medical grade polyethylene-based skeletal implants exhibit osteo-disintegration, erosion, and modest hemocompatibility. Herein, we report on the fabrication of highly adherent undoped and Si-containing DLC (Si-DLC) coatings for biomedical implant applications by utilizing plasma and laser-based processing techniques on thermally sensitive polyethylene (PE) substrates. Scratch testing reveals a strong interfacial shear strength of 620 MPa for DLC coatings deposited on PE. A contact stress of ∼32 MPa induced cracking of the DLC thin film. The Si-DLC films demonstrated a higher critical failure load and less cracking compared to undoped DLC films. The contact angle for PE increased from 90° to 110° when it was coated with the Si-DLC thin film. A high optical bandgap of 2.5 eV was calculated for the 21 at% Si-DLC thin films. Pulsed laser annealing (PLA) of Si-DLC films at 0.3 J cm⁻² increased the amount of sp² bonded carbon, resulting in an improvement in lubricity, hydrophobicity, and electrical conductivity properties. In addition, the laser patterned pristine DLC films showed the formation of reduced graphene oxide, which possessed sizeable properties for wearable electronics and biosensing applications (R_s = 0.6 kΩ □⁻¹). This study indicates that PLA is a useful technique for modifying the properties of DLC thin films on flexible polymeric substrates for state-of-the-art biomedical and electronic sensing applications.

Opioid drugs are extremely potent synthetic analytes, and their abuse is common around the world. Hence, a rapid and point-of-need device is necessary to assess the presence of this compound in body fluid so that a timely countermeasure can be provided to the exposed individuals. Herein, we present an attractive microneedle sensing platform for the detection of the opioid drug fentanyl in real serum samples using an electrochemical detection method. The device contained an array of pyramidal microneedle structures that were integrated with platinum (Pt) and silver (Ag) wires, each with a microcavity opening. The working sensor was modified by graphene ink and subsequently with 4 (3-Butyl-1-imidazolio)-1-butanesulfonate) ionic liquid. The microneedle sensor showed direct oxidation of fentanyl in liquid samples with a detection limit of 27.8 μM by employing a highly sensitive square-wave voltammetry technique. The resulting microneedle-based sensing platform displayed an interference-free fentanyl detection in diluted serum without conceding its sensitivity, stability, and response time. The obtained results revealed that the microneedle sensor holds considerable promise for point-of-need fentanyl detection and opens additional opportunities for detecting substances of abuse in emergencies.