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This study reports on the first all-printed vertically stacked organic electrochemical transistors (OECTs) operating in accumulation mode; the devices, relying on poly([4,4?-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-2,2?-bithiophen-5,5?-diyl]-alt-[thieno[3,2-b]thiophene-2,5-diyl]) (pgBTTT) as the active channel material, are fabricated via a combination of screen and inkjet printing technologies. The resulting OECTs (W/L ≈5) demonstrate good switching performance; gm, norm ≈13 mS cm?1, µC* ≈21 F cm?1 V?1 s?1, ON?OFF ratio > 104 and good cycling stability upon continuous operation for 2 h. The inkjet printing process of pgBTTT is established by first solubilizing the polymer in dihydrolevoglucosenone (Cyrene), a non-toxic, cellulose-derived, and biodegradable solvent. The resulting ink formulations exhibit good jettability, thereby providing reproducible and stable p-type accumulation mode all-printed OECTs with high performance. Besides the environmental and safety benefits of this solvent, this study also demonstrates the assessment of how the solvent affects the performance of spin-coated OECTs, which justifies the choice of Cyrene as an alternative to commonly used harmful solvents such as chloroform, also from a device perspective. Hence, this approach shows a new possibility of obtaining more sustainable printed electronic devices, which will eventually result in all-printed OECT-based logic circuits operating in complementary mode., This project received funding from the European Union's Horizon 2020 research and innovation program under grant agreement no. 964677 (MITICS). The authors would like to thank Jessica Åhlin for valuable electrolyte discussions. A.M. and P.A.E. thank Vinnova for financial support (grant agreement no. 2023-01337). W.M., L.B., and A.G. thank the FWO Vlaanderen for financial support (WEAVE project G025922N and Ph.D. grant 1S70122N)

Technological advances and applications of printed electronic devices rely on novel organic semiconductor (OSC) materials and cutting-edge advanced manufacturing technologies. A growing number of solution- processable organic electronic materials has paved the way towards cost- efficient fabrication techniques, fostering the growth and emergence of printed electronics research in recent decades. Organic semiconductor materials are unique because of mixed ionic and electronic transport of charges that may translate biological signals into electrical ones or vice versa. The organic electrochemical transistor (OECT) is a type of transistor where the active material (channel) is made of an organic mixed ionic-electronic conductor (OMIEC). Since OECTs may serve as organic bioelectronic devices that encompass high ionic and electronic conductivity, they also represent a groundbreaking technology by forming communication channels between living systems and external electronic circuits used for recording. Highly conductive and stable OMIECs, sustainable solvents for ink formulations, bio-based substrates, new device architectures and redefined manufacturing strategies are the keys that unlock highly sensitive OECT-based (bio)sensor devices and OECT-based electronic circuits with high gain and low power consumption. This dissertation explores and unveils the effects of different additive manufacturing strategies, channel materials, ink formulations and device architectures on the performance and applications of all-printed OECT devices. The key findings of this thesis are summarized in four first-authored scientific journal articles. In the first article, we redefined the manufacturing approach to create high performance all-printed OECTs exhibiting very short switching times; this approach was further verified by printing OECT-based inverters operating at a frequency beyond 100 Hz and five-stage ring oscillators. In the second article, we developed an all-printed sensor, Teknologiska framsteg och tillämpningar inom tryckt elektronik är beroende av nya organiska halvledarmaterial och avancerad tillverkningsteknik. Ett stort urval av organiska elektroniska material och kostnadseffektiva additiva tillverkningstekniker har möjliggjort framväxten av forskningsområdet tryckt elektronik under de senaste decennierna. Organiska halvledarmaterial är unika, dels för att de kan processas från lösning, men också på grund av att kombinationen av både jon- och elektrontransport kan användas för att översätta biologiska signaler till elektriska, eller vice versa. En organisk elektrokemisk transistor (OECT) är en typ av transistor där det aktiva kanalmaterialet är baserat på ett organiskt material som leder både joner och elektroner, t.ex. en konjugerad polymer. Tack vare detta kan OECTs användas inom bioelektroniska tillämpningar, som banbrytande teknik för att underlätta kommunikationen mellan levande system och elektronisk mätutrustning. Organiska halvledare med hög ledningsförmåga och bra stabilitet, miljövänliga lösningsmedel för bläckformuleringar, biobaserade substrat, nya komponentstrukturer och nytänkande kring tillverkningsstrategier är viktiga parametrar för att erhålla hög känslighet i OECT-baserade (bio)sensorer samt OECT-baserade elektroniska kretsar med hög förstärkning och låg effektförbrukning. Denna avhandling syftar till att utforska och förstå hur olika additiva tillverkningsstrategier, material, bläckformuleringar och komponentstrukturer påverkar prestandan hos helt tryckta OECTs, och i vilka tillämpningsområden de kan användas. De viktigaste resultaten av detta arbete sammanfattas i fyra artiklar. I den första artikeln kombinerade vi två olika tryckteknologier för att skapa högpresterande heltryckta OECTs med korta switchtider; detta tillvägagångssätt verifierades också genom att trycka ringoscillatorer samt OECT-baserade inverterare som kunde drivas vid en frekvens på över 100 Hz. I den andra artikeln utvecklade vi helt tr

This work demonstrates sensitive and low-cost piezoelectric sensors on skin-friendly, ultrathin, and conformable substrates combined with organic electrochemical transistors (OECTs) for the detection and amplification of alternating low-voltage input signals. The fully screen-printed (SP) piezoelectric sensors were manufactured on commercially available tattoo paper substrates, while the all-printed OECTs, relying on an extended gate electrode architecture, were manufactured either by solely using SP or by combining SP and aerosol jet printing (AJP) on PET substrates. Applying a low-voltage signal (±25 mV) to the gate electrode of the SP+AJP OECT results in approximately five times higher current modulation as compared to the fully SP reference OECT. The tattoo paper-based substrate enables transfer of the SP piezoelectric sensor to the skin, which in turn allows for radial pulse monitoring when combined with the SP+AJP OECT; this is possible due to the ability of the conformable sensor to convert mechanical vibrations into voltage signals along with the highly sensitive current modulation ability of the transistor device to further amplify the output signal. The results reported herein pave the way toward all-printed fully conformable wearable devices with high sensitivity to be further utilized for the real-time monitoring of electrophysiological signals.

Microfluidic surface chemistry can enable control of capillary-driven flow without the need for bulky external instrumentation. A novel pondered nonhomogeneous coating defines regions with different wetting properties on the microchannel walls. It changes the curvature of the liquid–air meniscus at various channel cross-sections and consequently leads to different capillary pressures, which is favorable in the strive toward automatic flow control. This is accomplished by the deposition of hydrophilic coatings on the surface of multilevel 3D-printed (3DP) microfluidic devices via inkjet printing, thereby retaining the surface hydrophilicity for at least 6 months of storage. To the best of our knowledge, this is the first demonstration of capillary flow control in 3DP microfluidics enabled by inkjet printing. The method is used to create “stop” and “delay” valves to enable preprogrammed capillary flow for sequential release of fluids. To demonstrate further utilization in point-of-care sensing applications, screen printed organic electrochemical transistors are integrated within the microfluidic chips to sense, sequentially and independently from external actions, chloride anions in the (1–100) × 10-3 m range. The results present a cost-effective fabrication method of compact, yet comprehensive, all-printed sensing platforms that allow fast ion detection (<60 s), including the capability of automatic delivery of multiple test solutions., Peer Reviewed, Postprint (published version)

Microfluidic surface chemistry can enable control of capillary-driven flow without the need for bulky external instrumentation. A novel pondered nonhomogeneous coating defines regions with different wetting properties on the microchannel walls. It changes the curvature of the liquid–air meniscus at various channel cross-sections and consequently leads to different capillary pressures, which is favorable in the strive toward automatic flow control. This is accomplished by the deposition of hydrophilic coatings on the surface of multilevel 3D-printed (3DP) microfluidic devices via inkjet printing, thereby retaining the surface hydrophilicity for at least 6 months of storage. To the best of our knowledge, this is the first demonstration of capillary flow control in 3DP microfluidics enabled by inkjet printing. The method is used to create “stop” and “delay” valves to enable preprogrammed capillary flow for sequential release of fluids. To demonstrate further utilization in point-of-care sensing applications, screen printed organic electrochemical transistors are integrated within the microfluidic chips to sense, sequentially and independently from external actions, chloride anions in the (1–100) × 10−3 m range. The results present a cost-effective fabrication method of compact, yet comprehensive, all-printed sensing platforms that allow fast ion detection (<60 s), including the capability of automatic delivery of multiple test solutions. © 2023 The Authors., Correspondence Address: P. Andersson Ersman; RISE Research Institutes of Sweden, Digital Systems, Smart Hardware, Printed, Bio- and Organic Electronics, Norrköping, 60233, Sweden. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska‐Curie grant agreement no. 813863 (BORGES).

This work demonstrates a novel fabrication approach based on the combination of screen and aerosol jet printing to manufacture fully printed organic electrochemical transistors (OECTs) and OECT-based logic circuits on PET substrates with superior performances. The use of aerosol jet printing allows for a reduction of the channel width to ≈15 µm and the estimated volume by a factor of ≈40, compared to the fully screen printed OECTs. Hence, the OECT devices and OECT-based logic circuits fabricated with the proposed approach emerge with a high ON/OFF ratio (103?104) and remarkably fast switching response, reaching an ON/OFF ratio of >103 in 4?8 ms, which is further demonstrated by a propagation delay time of just above 1 ms in OECT-based logic inverter circuits operated at a frequency of 100 Hz. All-printed monolithically integrated OECT-based five-stage ring oscillator circuits further validated the concept with a resulting self-oscillation frequency of 60 Hz., Funding: This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 813863 (BORGES) and the European Union's Horizon 2020 research and innovation programme under the grant agreement No 825339 (WEARPLEX).