Free-electron lasing with compact beam-driven plasma wakefield accelerator.

The possibility to accelerate electron beams to ultra-relativistic velocities over short distances by using plasma-based technology holds the potential for a revolution in the field of particle accelerators1-4. The compact nature of plasma-based accelerators would allow the realization of table-top machines capable of driving a free-electron laser (FEL)5, a formidable tool to investigate matter at the sub-atomic level by generating coherent light pulses with sub-ångström wavelengths and sub-femtosecond durations6,7. So far, however, the high-energy electron beams required to operate FELs had to be obtained through the use of conventional large-size radio-frequency (RF) accelerators, bound to a sizeable footprint as a result of their limited accelerating fields. Here we report the experimental evidence of FEL lasing by a compact (3-cm) particle-beam-driven plasma accelerator. The accelerated beams are completely characterized in the six-dimensional phase space and have high quality, comparable with state-of-the-art accelerators8. This allowed the observation of narrow-band amplified radiation in the infrared range with typical exponential growth of its intensity over six consecutive undulators. This proof-of-principle experiment represents a fundamental milestone in the use of plasma-based accelerators, contributing to the development of next-generation compact facilities for user-oriented applications9.

Use of perampanel oral suspension for the treatment of refractory and super-refractory status epilepticus.

INTRODUCTION: Status epilepticus (SE) is a medical emergency associated with a significant risk of disability and death. The treatment of SE follows a step-wise approach, with limited data on ideal antiseizure medications (ASMs) for refractory and super refractory SE (RSE/SRSE). Perampanel (PER), an AMPA receptor antagonist, has shown promise in animal models but still has limited data in humans. This study tried to evaluate optimal dosage and safety of PER in RSE and SRSE patients. MATERIALS AND METHODS: We retrospectively analysed 17 adult patients with RSE (1) or SRSE (16) treated with PER. Demographic and clinical data, including EEG patterns, ASMs administered, PER dosages, and PER plasma concentrations, were collected. For patients receiving a 24 mg PER loading dose (full dose group), the following treatment regimen was applied: 24 mg per day for 48 h following by 16 mg per day. The response to PER was assessed based on electroencephalographic (EEG) improvement from high to low epileptiform activity or from low to the absence of epileptiform activities. Safety was evaluated monitoring hepatic and renal function. RESULTS: A response rate of 58.82 % was observed, with significantly higher responses in the full dose group (81.82 %) compared to those receiving PER doses below 24 mg (low dose group) (16.67 %) (p-value = 0.004; OR 0.044, 95 % CI 0.003 to 0.621, p = 0.021). No other clinical factors significantly influenced treatment response. Hepatic enzymes become elevated in most patients (70.59 %) but spontaneously decreased. DISCUSSION: Our findings suggest that a 24 mg PER dose administered for 48 h may be more effective in managing RSE and SRSE compared to doses below 24 mg, potentially due to pharmacokinetic factors. CONCLUSION: More robust data on PER in RSE and SRSE, including standardized dosing procedures and plasma level monitoring are needed. PER's potential benefits should be explored further, particularly in patients with RSE and SRSE.

Criteria for melanocytic lesions in LC-OCT.

BACKGROUND: Line-field confocal optical coherence tomography (LC-OCT) is an emerging diagnostic tool with imaging depth reaching ~400 µm and a novel three-dimensional (3D) cube providing cellular resolution. As far as we are aware, there are only a limited number of papers that have reported diagnostic criteria for melanocytic lesions using this technique, and none of them have been multicentric. OBJECTIVES: Our aim was to establish the diagnostic criteria for melanocytic lesions using LC-OCT and identify the most significant architectural and cytologic features associated with malignancy. METHODS: A retrospective evaluation of 80 consecutive melanocytic lesions from a prospective multicentric data set spanning three European centres was conducted. We excluded facial, acral and mucosal lesions from the study. Dermoscopic and LC-OCT images were evaluated by a consensus of four observers. Multivariate logistic regression with backward elimination was employed. RESULTS: The main melanoma diagnostic criteria include detecting >10 pagetoid cells in 3D acquisition, irregular 3D epidermal architecture, disrupted dermoepidermal junction (DEJ) and clefting. Significant risk factors were irregular 3D epidermal architecture, >10 pagetoid cells, dendritic cells at DEJ without underlying inflammation. Novel malignancy criteria in vertical view were DEJ disruption and clefting around atypical melanocyte nests. Exclusive melanoma features were epidermal nests, epidermal consumption, dense dermal nests with atypia. Protective features in the absence of any malignancy indicators were DEJ ring pattern, cobblestone, elongated rete ridges (vertical), well-defined DEJ and wave pattern (vertical). CONCLUSIONS: A series of diagnostic criteria for the identification of melanocytic lesions with LC-OCT have been established. Validation of these criteria in clinical practice through future studies is essential to further establish their utility.

Stable Operation of a Free-Electron Laser Driven by a Plasma Accelerator.

The breakthrough provided by plasma-based accelerators enabled unprecedented accelerating fields by boosting electron beams to gigaelectronvolt energies within a few centimeters [1-4]. This, in turn, allows the realization of ultracompact light sources based on free-electron lasers (FELs) [5], as demonstrated by two pioneering experiments that reported the observation of self-amplified spontaneous emission (SASE) driven by plasma-accelerated beams [6,7]. However, the lack of stability and reproducibility due to the intrinsic nature of the SASE process (whose amplification starts from the shot noise of the electron beam) may hinder their effective implementation for user purposes. Here, we report a proof-of-principle experiment using plasma-accelerated beams to generate stable and reproducible FEL light seeded by an external laser. FEL radiation is emitted in the infrared range, showing the typical exponential growth of its energy over six consecutive undulators. Compared to SASE, the seeded FEL pulses have energies 2 orders of magnitude larger and stability that is 3 times higher.

Ink-jet printing and drop-casting deposition of 2H-phase SnSe2and WSe2nanoflake assemblies for thermoelectric applications.

The development of simple, scalable, and cost-effective methods to prepare Van der Waals materials for thermoelectric applications is a timely research field, whose potential and possibilities are still largely unexplored. In this work, we present a systematic study of ink-jet printing and drop-casting deposition of 2H phase SnSe2and WSe2nanoflake assemblies, obtained by liquid phase exfoliation, and their characterization in terms of electronic and thermoelectric properties. The choice of optimal annealing temperature and time is crucial for preserving phase purity and stoichiometry and for removing dry residues of ink solvents at inter-flake boundaries, while maximizing the sintering of nanoflakes. An additional pressing is beneficial to improve nanoflake orientation and packing, thus enhancing electric conductivity. In nanoflake assemblies deposited by drop casting and pressed at 1 GPa, we obtained thermoelectric power factors at room temperature up to 2.2 × 10-4mW m-1K-2for SnSe2and up to 3.0 × 10-4mW m-1K-2for WSe2.

Invited review: Hygienic quality, composition, and technological performance of raw milk obtained by robotic milking of cows.

Automatic milking systems (AMS), first introduced on dairy farms in the 1990s, rapidly spread across many countries. This technology is based on the voluntary milking of dairy cattle in a completely automated process, which relies on computer management, with a substantial average increase in milking frequency. Compared with conventional milking, AMS significantly alters herd management, with important implications on economic, technical, and social aspects of farming, on animal physiology, health, and well-being. These aspects are explored in an extensive body of research. In contrast, the effects of AMS adoption on milk quality are often overlooked. This review draws together both positive and negative effects of AMS on the milk production chain, particularly emphasizing the variations of hygienic and compositive characteristics of raw milk and their interplay, as compared with milk obtained with conventional milking. Scattered and sometimes conflicting literature exists on whether and how these variations may influence quality and yield of the derived dairy products. Current scientific knowledge on these crucial aspects is thus reviewed, with particular focus on milk technological suitability for being processed into dairy products having the target characteristics in terms of taste, structure, on-storage stability, and sustainability. Provided the managing conditions are optimized, AMS allow increased milk production, mostly due to more frequent milking, without compromising the milk characteristics that are crucial to food industry for processing. Nevertheless, specific biochemical aspects related to the changed milking interval, which determines the duration of enzyme activities and bacterial growth in milk, need further research.

Effect of temperature on the microstructure of fat globules and the immunoglobulin-mediated interactions between fat and bacteria in natural raw milk creaming.

Natural creaming of raw milk is the first step in production of Grana Padano and Parmigiano Reggiano Protected Denomination of Origin cheeses. This process decreases the fat content and plays an important role in the removal of clostridia species that may cause late-blowing defects in ripened cheeses. Partial coalescence of fat globules-that may influence fat behavior in cheese making and affect the microstructure of fat in the final cheese product-was observed at creaming temperatures higher than 22°C by confocal laser scanning microscopy. The widespread practice of heating of milk at 37°C before creaming at 8°C resulted in important changes in the size distribution of fat globules in raw milk, potentially altering the ability of fat to entrap clostridia spores. We investigated the role of immunoglobulin classes in both the clustering of fat globules and the agglutination of Clostridium tyrobutyricum to fat globules during creaming. Immunogold labeling and transmission electron microscopy showed that IgA and IgM but not IgG were involved in both clustering and agglutination. Both vegetative cells and spores were clearly shown to agglutinate to fat droplets, a process that was suppressed by thermal denaturation of the immunoglobulins. The debacterization of raw milk through natural creaming was improved by the addition of purified immunoglobulins. Overall, these findings provide not only a better understanding of the phenomena occurring during the natural creaming but also practical insights into how the process of creaming may be optimized in cheese production plants.

Lysozyme affects the microbial catabolism of free arginine in raw-milk hard cheeses.

Lysozyme (LZ) is used in several cheese varieties to prevent late blowing which results from fermentation of lactate by Clostridium tyrobutyricum. Side effects of LZ on lactic acid bacteria population and free amino acid pattern were studied in 16 raw-milk hard cheeses produced in eight parallel cheese makings conducted at four different dairies using the same milk with (LZ+) or without (LZ-) addition of LZ. The LZ-cheeses were characterized by higher numbers of cultivable microbial population and lower amount of DNA arising from lysed bacterial cells with respect to LZ + cheeses. At both 9 and 16 months of ripening, Lactobacillus delbrueckii and Lactobacillus fermentum proved to be the species mostly affected by LZ. The total content of free amino acids indicated the proteolysis extent to be characteristic of the dairy, regardless to the presence of LZ. In contrast, the relative patterns showed the microbial degradation of arginine to be promoted in LZ + cheeses. The data demonstrated that the arginine-deiminase pathway was only partially adopted since citrulline represented the main product and only trace levels of ornithine were found. Differences in arginine degradation were considered for starter and non-starter lactic acid bacteria, at different cheese ripening stages.

New insight on crystal and spot development in hard and extra-hard cheeses: Association of spots with incomplete aggregation of curd granules.

Chemical composition and structure of different types of macroparticles (specks, spots) and microparticles (microcrystals) present in hard and extra-hard cheeses were investigated. Light microscopy revealed that the small hard specks had the structure of crystalline tyrosine, as confirmed by amino acid analysis. Spots showed a complex structure, including several curd granules, cavities, and microcrystals, and were delimited by a dense protein layer. Spots contained less moisture and ash than the adjacent cheese area, and more protein, including significantly higher contents of valine, methionine, isoleucine, leucine, tyrosine, and phenylalanine. Microcrystals were observed by light and electron microscopy and analyzed by confocal micro-Raman. Among others, calcium phosphate crystals appeared to consist of a central star-shaped structure immersed in a matrix of free fatty acids plus leucine and phenylalanine in free form or in small peptides. A hypothetical mechanism for the formation of these structures has been formulated.

Mechanisms of Clostridium tyrobutyricum removal through natural creaming of milk: A microscopy study.

Clostridium tyrobutyricum is the main spoilage agent of late blowing defect (LBD) in Grana Padano and Parmigiano-Reggiano cheeses; LBD is characterized by openings and holes and is sometimes accompanied by cracks and an undesirable flavor. Even a very few spores remaining in the cheese curd may cause LBD; thus, it is essential to eradicate them during milk natural creaming. By this process, most of the bacteria, somatic cells, and spores rise to the top of the milk, together with the fat globules, and are removed with the cream. Previous studies suggested that milk immunoglobulins mediate the interactions between fat globules and bacteria that occur upon creaming but no direct evidence for this has been found. Moreover, other physical chemical interactions could be involved; for example, physical entrapment of spores among globule clusters. To maximize the efficiency of the natural creaming step in removing Cl. tyrobutyricum, it is essential to understand the nature of spore-globule interactions. With this aim, raw milk was contaminated with spores of Cl. tyrobutyricum before going to creaming overnight at 8°C, after which spore and bacteria removal was >90%. The obtained cream was analyzed by light interference contrast and fluorescence microscopy and by transmission electron microscopy (TEM). Results showed that most of the vegetative cells and spores, which were stained with malachite green before addition to milk, adhered tightly to the surface of single fat globules, the membranes of which appeared heterogeneous when stained with the fluorescent dye DilC18(3)-DS. Using the same dye, we observed transient and persistent interactions among globules, with formation of clusters of different sizes and partial coalescence of adhering membranes. Transmission electron microscopy examination of replicates of freeze-fractured cream allowed us to observe tight adhesion of spores to fat globules. Ultrathin sections revealed that this adhesion is mediated by an amorphous, slightly electron-opaque material, sometimes granular in appearance. Bacteria also adhered to different fat globules, linking them together, which suggests that adhesion was strong enough to maintain a stable contact. Although we cannot exclude physical entrapment of bacteria among fat globule clusters, we show for the first time that most of the bacteria are adhered to fat globules by an electron-opaque material whose nature has yet to be determined. Immunoglobulins are certainly the best candidates for adhesion but other compounds may be involved.

Insights into fast-track colon surgery: a plea for a tailored program.

BACKGROUND: This retrospective study compared the fast-track colon surgery program to conventional perioperative care and assessed factors that influence postoperative length of stay. DESIGN: This retrospective study included 124 fast-track and 119 conventional care colon surgical patients. Exclusion criteria were primary rectal disease, stoma, American Society of Anesthesiologists score IV, and Association Française de Chirurgie index 3 or 4. Laparoscopy was the preferred approach. Variables influencing length of stay were analyzed by multivariate linear and logistic regression. RESULTS: Overall mortality and complication rates were not significantly different between groups (fast-track vs. controls 0 vs. 0.8 %, 30.6 vs. 38.6 % respectively). As expected, median length of stay was significantly reduced in fast-track patients (3 vs. 6 days, p < 0.001), but emergency readmission rate was higher (16.9 vs. 7.6 %, p = 0.026), although rehospitalization rates were similar (8 vs. 4.2 %, not significant). Independent risk factors of increased length of stay were identified as age >69 years (p = 0.001), laparotomy (p = 0.011), and conventional perioperative care (p < 0.001). CONCLUSIONS: The introduction of a fast-track program reduced postoperative length of stay without increasing complication rate. This study proposes a modulation of the program according to patient age and surgical approach.

Rapid determination of sodium in milk and milk products by capillary zone electrophoresis.

A capillary zone electrophoresis method for the determination of Na in milk and milk products was developed and compared with an International Organization for Standardization/International Dairy Federation standard method that is based on flame atomic absorption spectrometry. The adoption of a background electrolyte consisting of 10 mM imidazole adjusted to pH 3.75 by the addition of oxalic acid allowed baseline separation of Na from other milk cations and from Li ion, which was adopted as an internal standard. Method validation was performed and the results for linearity, precision, limit of detection, limit of quantification, and recovery are presented. The procedure was tested on commercial milk samples differing in fat content (whole, semiskimmed, and skimmed) and processing conditions (pasteurization, UHT sterilization, and microfiltration). The reliability of the method was confirmed for different varieties of cheese and other milk products. The method enables the routine measurement of Na content by a rapid and accurate capillary zone electrophoresis procedure.

Test of "crab-waist" collisions at the DAPhiNE Phi factory.

The electron-positron collider DAPhiNE, the Italian Phi factory, has been recently upgraded in order to implement an innovative collision scheme based on large crossing angle, small beam sizes at the crossing point, and compensation of beam-beam interaction by means of sextupole pairs creating a "crab-waist" configuration in the interaction region. Experimental tests of the novel scheme exhibited an increase by a factor of 3 in the peak luminosity of the collider with respect to the performances reached before the upgrade. In this Letter we present the new collision scheme, discuss its advantages, describe the hardware modifications realized for the upgrade, and report the results of the experimental tests carried out during commissioning of the machine in the new configuration and standard operation for the users.

AFM nanopatterning of transition metal oxide thin films.

In this paper we show diverse methods for patterning transition metal oxide (TMO) thin films by Local Anodic Oxidation (LAO) using an Atomic Force Microscope (AFM). At first, direct lithography by current-controlled LAO of TMO thin films and selective wet etching is presented. For insulating films or those whose AFM patterns cannot be selectively removed by wet etching, fabrication of nanomasks is required; thus, the fabrication of Molybdenum and TMO nanomasks is reported. As a further development, we show the AFM fabrication of Mo/poly(methylmethacrylate) (PMMA) nanomasks through multistep processes combining LAO of Mo and dry etching of PMMA. Detailed discussions and comparisons between these methods are presented.

Detection of milk powder and caseinates in Halloumi cheese.

Halloumi cheese is traditionally manufactured from fresh milk. Nevertheless, dried dairy ingredients are sometimes illegally added to increase cheese yield. Lysinoalanine and furosine are newly formed molecules generated by heating and drying milk protein components. The levels of these molecular markers in the finished Halloumi have been investigated to verify their suitability to reveal the addition of skim milk powder and calcium caseinate to cheese milk. Because of the severe heating conditions applied in curd cooking, genuine Halloumi cheeses (n=35), representative of the Cyprus production, were characterized by levels of lysinoalanine (mean value=8.1 mg/100g of protein) and furosine (mean value=123 mg/100g of protein) unusual for natural cheeses. Despite the variability of the values, a good correlation between the 2 parameters (R=0.975) has been found in all cheeses, considering both the fresh and mature cheeses as well as those obtained from curd submitted to a prolonged cooking following a traditional practice adopted by a very small number of manufacturers. Experimental cheeses made by adding as low as 5% of skim milk powder, or calcium caseinate, or both, to cheese milk fell outside the prediction limits at +/-2 standard deviation of the above-reported correlation regardless of curd cooking conditions or ripening length. This correlation may be adopted as a reliable index of Halloumi cheese genuineness.

Bone turnover, osteopenia and vascular calcifications in hemodialysis patients. A histomorphometric and multislice CT study.

BACKGROUND: Several classical risk factors are at the base of vascular calcifications in hemodialysis patients. Among these, according to a general opinion, also bone turnover plays a role, which, however, requires a better definition. In addition, it has been suggested that there is a relationship between primary osteoporosis and vascular calcifications. This bone biopsy-based study on a hemodialysis patient cohort is a contribution to the evaluation of these alleged relations. METHODS: This study has been carried out on a cohort of 32 patients on maintenance hemodialysis, who were subjected to transiliac bone biopsy for histomorphometric, histodynamic and bone aluminum deposit evaluation. The patients were also examined with multislice computerized tomography for quantitation of heart and coronary calcifications. RESULTS: The patients were affected by renal osteodystrophy with a wide range of bone formation rate values. A significant negative correlation was found between the rate of bone turnover and log-transformed cardiac calcification score (p < 0.003). There were also negative significant correlations between the cardiac and coronary calcification score log and trabecular number (p < 0.02 and p < 0.05, respectively), while the correlations were positive with trabecular separation (p < 0.03 and p < 0.05, respectively). However, multiregression analysis, forward method, selected only age, hemodialysis age and serum Ca as predictive variables of cardiac and coronary calcification score log, while the histomorphometric and histodynamic variables were excluded. CONCLUSIONS: In this study, in spite of the suggestive findings of the univariate statistical approach, a further multivariate analysis was indicative of a spurious association between calcification scores and both bone turnover and histomorphometric parameters of trabecular mass and connectivity. Bone turnover and trabecular mass do not appear to be prominently connected with the extent of cardiac and coronary calcifications in hemodialysis patients.

A fluorescence in situ staining method for investigating spores and vegetative cells of Clostridia by confocal laser scanning microscopy and structured illuminated microscopy.

Non-pathogenic spore-forming Clostridia are of increasing interest due to their application in biogas production and their capability to spoil different food products. The life cycle for Clostridium includes a spore stage that can assist in survival under environmentally stressful conditions, such as extremes of temperature or pH. Due to their size, spores can be investigated by a range of microscopic techniques, many of which involve sample pre-treatment. We have developed a quick, simple and non-destructive fluorescent staining procedure that allows a clear differentiation between spores and vegetative cells and effectively stains spores, allowing recovery and tracking in subsequent experiments. Hoechst 34580, Propidium iodide and wheat germ agglutinin WGA 488 were used in combination to stain four strains of Clostridia at different life cycle stages. Staining was conducted without drying the sample, preventing changes induced by dehydration and cells observed by confocal laser scanner microscopy or using a super-resolution microscope equipped with a 3D-structured illumination module. Dual staining with Hoechst/Propidium iodide differentiated spores from vegetative cells, provided information on the viability of cells and was successfully applied to follow spore production induced by heating. Super-resolution microscopy of spores probed by Hoechst 34580 also allowed chromatin to be visualised. Direct staining of a cheese specimen using Nile Red and Fast Green allowed in situ observation of spores within the cheese and their position within the cheese matrix. The proposed staining method has broad applicability and can potentially be applied to follow Clostridium spore behaviour in a range of different environments.

Microfiltration and ultra-high-pressure homogenization for extending the shelf-storage stability of UHT milk.

Fat separation, gelation or sedimentation of UHT milk during shelf-storage represent instability phenomena causing the product rejection by consumers. Stability of UHT milk is of increasing concern because access to emerging markets currently implies for this product to be stable during shipping and prolonged storage, up to 12 months. The role of microfiltration prior to UHT process in avoiding or retarding the gelation or sediment formation was studied by comparing microfiltered UHT milk to conventional UHT milk. A second trial was set up to study the effects of double ultra-high pressure homogenization in delaying the cream rising and UHT milk homogenized once at lower pressure was taken as control. All milk samples were produced at industrial plant level. Milk packages were stored at 22 °C, opened monthly for visually inspecting the presence of cream layer, gel or sediment and then analysed. Microfiltration markedly delayed the formation of both gel particles and sediment, with respect to the control, and slowed down the proteolysis in terms of accumulation of peptides although no correlation was observed between the two phenomena. The double homogenization, also evaluated at ultra-structural level, narrowed the fat globule distribution and the second one (400 MPa), performed downstream to the sterilization step, disrupted the fat-protein aggregates produced in the first one (250 MPa). The adopted conditions avoided the appearance of the cream layer in the UHT milk up to 18 months. This study contributes important knowledge for developing strategies to delay instability phenomena in UHT milk destined to extremely long shelf storage.

Impact assessment of traditional food manufacturing: The case of Grana Padano cheese.

The dairy sector is recognised as one of the most impacting agricultural activities. In Italy approximately 24% of cow's milk is destined to Grana Padano, a Protected Designation of Origin long ripening cheese. The Grana Padano production has increased by 10% in the last decade and approximately reached 183,000 t in 2015. Around 38% of this production is exported to Germany, US, France and to the rest of the world. This study evaluated the environmental impact of production of Grana Padano, through a "cradle to cheese factory gate" Life Cycle Assessment. The study involved an Italian cheese factory that produces about 3.6% of the total production of Grana Padano cheese and a group of 5 dairy farms, chosen among the farms that sold all milk produced to the cheese factory. The functional unit was 1 kg of Grana Padano cheese 12-month ripened. Environmental impacts of co-products: whey, cream, butter and buttermilk were also evaluated. Two sensitivity analyses were conducted: the first one had the aim to explore the effect of different allocation methods based on dry matter content, economic or nutritive value of cheese, respectively; the second one considered the variation of the impacts of milk production and its effect on cheese environmental impact. Milk production phase gave the most important contribution to the environmental impact of cheese, with a percentage of 93.5-99.6% depending on the impact category. Excluding milk production from the system boundary, milk transport and use of electricity were the main responsible of the environmental impact of cheese-making process. The climate change impact for the production of 1 kg Grana Padano was 10.3 kg of CO2 eq, using a dry matter allocation method, while 16.9 and 15.2 kg of CO2 eq adopting economic and nutritive value allocation methods, respectively.

Ultralow friction of ink-jet printed graphene flakes.

We report the frictional response of few-layer graphene (FLG) flakes obtained by the liquid phase exfoliation (LPE) of pristine graphite. To this end, we inkjet print FLG on bare and hexamethyldisilazane-terminated SiO2 substrates, producing micrometric patterns with nanoscopic roughness that are investigated by atomic force microscopy. Normal force spectroscopy and atomically-resolved morphologies indicate reduced surface contamination by solvents after a vacuum annealing process. Notably, the printed FLG flakes show ultralow friction comparable to that of micromechanically exfoliated graphene flakes. Lubricity is retained on flakes with a lateral size of a few tens of nanometres, and with a thickness as small as ∼2 nm, confirming the high crystalline quality and low defects density in the FLG basal plane. Surface exposed step edges exhibit the highest friction values, representing the preferential sites for the origin of the secondary dissipative processes related to edge straining, wear or lateral displacement of the flakes. Our work demonstrates that LPE enables fundamental studies on graphene friction to the single-flake level. The capability to deliver ultralow-friction-graphene over technologically relevant substrates, using a scalable production route and a high-throughput, large-area printing technique, may also open up new opportunities in the lubrication of micro- and nano-electromechanical systems.